NINETEENTH INTERNATIONAL SUMMER SCHOOL ON
VACUUM, ELECTRON AND ION TECHNOLOGIES
21 - 25 September 2015
SOZOPOL, BULGARIA
PROGRAM
ABSTRACTS
Editors: M. Dimitrova, M. Damyanova, Ch. Ghelev and E. Vasileva
INSTITUTE OF ELECTRONICS
BULGARIAN ACADEMY OF SCIENCES
72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria
Phone: +359 2 875 0077, Fax: +359 2 975 32 01, http://www.ie-bas.dir.bg
The Institute of Electronics carries out research and educational activities in the
fields of Physical Electronics, Quantum Electronics and Radiophysics. The research is
focused on: studying the processes of generation and control of beams of electrons, ions and
photons, and especially on their interaction with matter; development of experimental and
industrial equipment for surface modification, thin-film deposition and analysis; welding
and melting of metals; low-temperature plasma, and plasma-chemical processes; plasmaassisted formation of thin films and coatings; interaction of laser radiation with matter and
thin-film formation; development of laser sources and systems for spectroscopy, metrology,
modification and analysis of materials; non-linear optical phenomena in fibers and
semiconductors; generation and propagation of electromagnetic waves; non-linear
phenomena in a wide MW-frequency range; scattering of electromagnetic waves from
homogeneous and inhomogeneous media, signal detection, data acquisition and processing;
development of electronic systems for the MW and optical ranges; systems for remote
sounding of the atmosphere and sensing of the sea and Earth surface.
DUTCH INSTITUTE FOR FUNDAMENTAL ENERGY RESEARCH
FOM Institute DIFFER, De Zaale 20, 5612 AJ Eindhoven, The Netherlands
Phone: +31 (0) 40 333 49 99, https://www.differ.nl/en
DIFFER was started in 2012 as the focal energy research activity of the Dutch
organisation for scientific research NWO and of its physics branch FOM, the foundation for
fundamental research on matter. The institute expands the previous FOM Institute for
Plasma Physics Rijnhuizen into a multidisciplinary national home for basic energy research.
We perform fundamental energy research in the fields of nuclear fusion and solar fuels,
actively working together with academic researchers. DIFFER also connects to research and
development at enterprises and industries. To accelerate technology innovation, we are
building an active national community on energy research.
DIFFER has two fusion research programs, which both address high priority topics in
the European Fusion Roadmap. We explore the intense plasma surface interactions expected
at the wall of future fusion power plants with our unique high-flux plasma generators
Magnum-PSI and Pilot- PSI.
On the shorter timescale, the big challenge in the energy transition is to integrate
fluctuating sustainable electricity in an infrastructure which demands predictable power
production. This is closely connected to the issue of global energy storage and transport, and
at DIFFER we aim to tackle this challenge by converting intermittent sustainable energy
into fuels. For instance, DIFFER investigates the splitting of water into hydrogen or the
activation of carbon dioxide into carbon monoxide, and the processing of these products
into a hydrocarbon fuel. The research involves the synthesis and design of novel materials
and processes to obtain scalable, efficient and cost-effective systems.
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
ORGANIZED BY
INSTITUTE OF ELECTRONICS
BULGARIAN ACADEMY OF SCIENCES, SOFIA, BULGARIA
DUTCH INSTITUTE FOR FUNDAMENTAL ENERGY RESEARCH
EINDHOVEN, THE NETHERLANDS
CO-FINANCED BY
the MINISTRY OF EDUCATION
AND SCIENCE of BULGARIA
CHAIRS OF THE SCHOOL
M. Dimitrova,
Institute of Electronics, Bulgarian Academy of Sciences, Sofia, Bulgaria
M.C.M. van de Sanden,
Dutch Institute for Fundamental Energy Research, Eindhoven, The Netherlands
INTERNATIONAL ADVISORY COMMITTEE
Bulgarian Academy of Sciences, Sofia, Bulgaria
Czech Academy of Sciences, Prague, Czech Republic
Czech Academy of Sciences, Prague, Czech Republic
Institut Jean Lamour (IJL), Ecole des Mines de Nancy, Nancy, France
Th. Czerwiec
Forschungszentrum Dresden-Rossendorf, Dresden, Germany
W. Möller
IOM and Leipzig University, Leipzig, Germany
B. Rauschenbach
IEAP University of Kiel, Kiel, Germany
H. Kersten
University of Patras, Patras, Greece
D. Mataras
Instituto Superior Técnico, Lisboa, Portugal
V. Guerra
National Institute for Laser, Plasma and Radiation Physics,
G. Dinescu
Magurele Bucharest, Romania
Institute of Physics, Belgrade, Serbia
Z. Petrovic
"Jozef Stefan" Institute, Ljubljana, Slovenia
M. Mozetic
Uppsala University, Uppsala, Sweden
K. Larsson
Uppsala University, Uppsala, Sweden
I. Katardjiev
M.C.M. (Richard) Dutch Institute for Fundamental Energy Research (DIFFER),
Eindhoven, The Netherlands
van de Sanden
Istanbul Technical University, Istanbul, Turkey
M. Ürgen
Sheffield Hallam University, Sheffield, UK
A. Ehiasarian
University of Illinois, Urbana, IL, USA
I. Petrov
N. Guerassimov
M. Dimitrova
R. Panek
4
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
LOCAL ORGANIZING COMMITTEE
Ch. Angelov, M. Damyanova, M. Dimitrova (Chair), Ch. Ghelev, E. Vasileva
MAIN SCIENTIFIC TOPICS:
• THIN FILMS DEPOSITION
• SURFACES AND THIN FILMS PROCESSING AND ANALYSIS
• COATINGS FOR ADVANCED APPLICATIONS
• PLASMA-SURFACE INTERACTION AND PLASMA DIAGNOSTICS
• MODELING AND COMPUTER SIMULATION
PLENARY AND POSTER SESSIONS:
A: PLASMA-SURFACE INTERACTION AND PLASMA DIAGNOSTICS.
MODELING AND COMPUTER SIMULATION
B: SURFACES AND THIN FILMS PROCESSING AND ANALYSIS
C: THIN FILMS DEPOSITION.
COATINGS FOR ADVANCED APPLICATIONS
ABBREVIATIONS:
TL – TOPIC LECTURE
PR – PROGRESS REPORT
OP – ORAL PRESENTATION
PA – POSTER SESSION A
PB – POSTER SESSION B
PC – POSTER SESSION C
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
PROGRAM
MONDAY, 21 SEPTEMBER
10:00
OFFICIAL OPENING
10:10 – 11:20 PLENARY SESSION 1
Chairman: S. Gateva
Title of the lecture
10:10
TL-1 M. Mozetic
Tailoring surface properties of delicate materials by neutral reactive plasma species
11:00
OP-1 T. Bogdanov
Theoretical investigation of coaxial discharge based on 1d fluid model
11:20 – 11:45 COFFEE BREAK
11:45 – 13:05 PLENARY SESSION 2
Chairman: P. Hovsepian
Title of the lecture
11:45
PR-1 R. Panek
Recent results in edge plasma studies on the
COMPASS tokamak
12:15
PR-2
M. Berta
Li-beam diagnostic system for the COMPASS tokamak
12:45
OP-2
P. Marinova
Reaction kinetics, heavy particles and rate
coefficients in HF and MW discharges in argon at atmospheric pressure
13:05
LUNCH
15:30 – 16:40 PLENARY SESSION 3
Chairman: R. Panek
Title of the lecture
15:30
PR-3 J. Gunn
Heat loads on tungsten divertor targets in
ITER
16:00
OP-3 E. Yordanova
Measurements of nonlinear susceptibility of
multicomponent glassy matrix processing by
using femto second z-scan method
16:20
OP-4 S. Karatodorov
Optical emission spectroscopy of plasma
produced by laser ablation of ferrous sulfide
16:40 – 17:00 COFFEE BREAK
17:00 – 19:00 POSTER SESSION A
20:00
WELCOME PARTY
Plasma-surface interaction and plasma diagnostics. Modeling and computer simulation
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
6
TUESDAY, 22 SEPTEMBER
10:00 – 11:20 PLENARY SESSION 4
Chairman: M. Mozetič
Title of the lecture
10:00
TL-2 J. Gerlach
Ion-beam assisted deposition of thin films
10:50
PR-4 G. Henrion
High time-resolution optical investigations
of PEO discharges: towards a better understanding of what is going on during plasma
electrolytic oxidation of light alloys
11:20 – 11:45 COFFEE BREAK
11:45 – 13:05 PLENARY SESSION 5
Chairman: M. Urgen
Title of the lecture
11:45
PR-5 N. Puac
OES and mass spectrometry characterization of atmospheric pressure plasma jets
12:15
PR-6 G. Dinescu
Atmospheric pressure processing with cold
radiofrequency plasma jets
12:45
OP-5 A. Kuzminova
Fabrication of metal oxide nanoparticles using gas aggregation source combined with
auxiliary oxygen RF plasma
13:05
LUNCH
15:30 – 16:50 PLENARY SESSION 6
Chairman: G. Dinescu
Title of the lecture
15:30
PR-7 M. Urgen
Effect of different bias modes on structure
and properties of coatings and diffusion layers produced by cathodic arc PVD
16:00
OP-6 A. Kovalenko
Gradual annealing effect and thermal stability of bulk-heterojunction solar cells using
DPP(TBFu)2 derivatives as donor materials
16:20
OP-7 G. Tsigaras
Detection of power formation in SiH4/H2
glow discharge
16:40
I. Petrov
IUVSTA
16:50 – 17:10 COFFEE BREAK
17:00 – 19:00 POSTER SESSION B
Surfaces and thin films processing and analysis.
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
WEDNESDAY, 23 SEPTEMBER
10:00 – 11:20 PLENARY SESSION 7
Chairman: J. Gerlach
Title of the lecture
10:00
TL-3 I. Petrov
Control of micro- and nanostructures in
transition metal nitrides: recent advances
10:50
PR-8 N. Ghafoor
Structuring on a nanoscale to manufacturing hard thin films
11:20 – 11:45 COFFEE BREAK
11:45 – 13:05 PLENARY SESSION 8
Chairman: J. F. Pierson
Title of the lecture
11:45
PR-9
From Ab-initio design to synthesis of multifunctional thin film coatings with enhanced
hardness and toughness
12:15
PR-10 P. Hovsepian
Three approaches to producing application
tailored Me-carbon films
12:45
OP-8 B. Blagoev
Resistivity in Al doped ZnO nanolayers obtained by atomic layer deposition
13:05
LUNCH
V. Chirita
15:30 – 16:40 PLENARY SESSION 9
Chairman: Z. Petrovic
Title of the lecture
15:30
PR-11 O. Yordanov
Fractal vs random field characterization of
complex morphologies and patterns
16:00
OP-9 V. Vrakatseli
Comparative study of RF reactive magnetron sputtering and SOL-GEL deposition of
UV induced superhydrophilic TiOx thin
films
16:20
OP-10 A. Ayrapetov
Stand for coating deposition and coating/material testing
16:40 – 17:00 COFFEE BREAK
17:00 – 19:00 POSTER SESSION C
Thin films deposition. Coatings for advanced applications
THURSDAY, 24 SEPTEMBER
10:00 – 11:20 PLENARY SESSION 10
Chairman: I. Petrov
Title of the lecture
10:00
Mesoscopic models as a tool to describe and
interpret surface phenomena
TL-4 V. Guerra
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
8
10:50
PR-12 J. F. Pierson
Local epitaxial growth effect in reactively
sputtered oxide thin films
11:20 – 11:45 COFFEE BREAK
11:45 – 13:05 PLENARY SESSION 11
Chairman: H. Kersten
Title of the lecture
11:45
PR-13 M. Gleeson
Surface interactions of plasma-generated
species
12:15
PR-14 G. van Rooji
Plasmolysis as a novel approach to CO2-tofuel conversion
12:45
OP-11 V. Sauchyn
Investigation of arc spot motion along the
electrodes in a plasma torch
13:05
LUNCH
14:00
EXCURSION
20:00
OFFICIAL DINNER
FRIDAY, 25 SEPTEMBER
10:00 – 11:20 PLENARY SESSION 12
Chairman: V. Guerra
Title of the lecture
10:00
TL-5 H. Kersten
Non-conventional plasma and sheath diagnostics
10:50
PR-15 A. Sobota
Atmospheric pressure plasma jets in helium
– the electric field and the charge delivered
to a dielectric surface
11:20 – 11:45 COFFEE BREAK
11:45 – 12:35 PLENARY SESSION 13 Title of the lecture
Chairman: N. Guerassimov
11:45
PR-16 V. Ignatova
ASML: Pushing the boundaries of what is
physically possible in precision engineering
12:05
OP-12 S. Boyadjiev
WO3 nanoparticles and WO3/TiO2 core-shell
nanocomposites prepared by annealing and
atomic layer deposition (ALD) for gas sensing, photocatalytic and electrochromic applications
12:25
CLOSING
13:00
LUNCH
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
ABSTRACTS
TOPIC LECTURES
Page
TL–1
M. Mozetič
Tailoring surface properties of delicate
materials by neutral reactive plasma species
21
TL–2
J.W. Gerlach
Ion-beam assisted deposition of thin films
22
TL–3
I. Petrov
Control of micro- and nanostructures in
transition metal nitrides: recent advances
23
TL–4
V. Guerra
Mesoscopic models as a tool to describe
and interpret surface phenomena
24
TL–5
H. Kersten, S. Bornoldt, A. Spethmann,
V. Schneider, T. Trottenberg
Non-conventional plasma and sheath diagnostics
26
PROGRESS REPORTS
Page
PR–1
R. Panek, J. Adamek, P. Bilkova,
Recent results in edge plasma studies on
P. Cahyna, R. Dejarnac, M. Dimitrova,
the COMPASS tokamak
P. Hacek, J. Havlicek, M. Hron,
M. Imrisek, M. Komm, T. Markovic,
M. Peterka, J. Seidl, J. Stockel,
P. Vondracek, V. Weinzettl and the
COMPASS team
29
PR–2
M. Berta, G. Anda, A. Bencze,
Li-beam diagnostic system for the COMD. Dunai, P. Hacek, J. Krbec, R. Panek, PASS tokamak
G. Veres, S. Zoletnik
30
PR–3
J. P. Gunn
Heat loads on tungsten divertor targets in
ITER
31
PR–4
G. Henrion, A. Nominé,
S.C. Troughton, J. Martin,
A.V. Nominé, T.W. Clyne, T. Belmonte
High time-resolution optical investigations of PEO discharges: towards a
better understanding of what is going
on during plasma electrolytic oxidation of light alloys
32
PR–5
N. Puač, D. Maletić, N. Selaković,
G. Malović and Z.Lj. Petrović
OES and mass spectrometry characterization of atmospheric pressure
plasma jets
33
PR–6
G. Dinescu
Atmospheric pressure processing
with cold radiofrequency plasma jets
34
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
10
Page
PR–7
M. Ürgen, S. Öncel
Effect of different bias modes on structure
and properties of coatings and diffusion
layers produced by cathodic arc PVD
34
PR–8
N. Ghafoor
Structuring on a nanoscale to manufacturing hard thin films
35
PR–9
V. Chirita
From Ab-initio design to synthesis of
multifunctional thin film coatings with
enhanced hardness and toughness
36
PR–10
P. Eh. Hovsepian and A. P. Ehiasarian
Three approaches to producing application tailored Me-carbon films
37
PR–11
O. Yordanov
Fractal vs random field characterization
of complex morphologies and patterns
38
PR–12
J.F. Pierson, Y. Wong, J. Ghanbaja,
F. Soldera, D. Horwat, F. Mücklich
Local epitaxial growth effect in reactively
sputtered oxide thin films
39
PR–13
M.A. Gleeson, T. Zahria, A.W. Kleyn, Surface interactions of plasma-generated
and M.C.M van de Sanden
species
40
PR–14
G.J. van Rooij, D.C.M. van den Bekerom, Plasmolysis as a novel approach to CO2N. den Harder, T. Minea,
to-fuel conversion
G. Berden, W.A. Bongers, R. Engeln,
M.F. Graswinckel, E. Zoethout, and
M.C.M. van de Sanden
41
PR–15
A. Sobota, E.T. Slikboer, O. Guaitella
Atmospheric pressure plasma jets in helium – the electric field and the charge
delivered to a dielectric surface
42
PR–16
V. Ignatova
ASML: Pushing the boundaries of what
is physically possible in precision engineering
43
CONTRIBUTED PAPERS
ORAL PRESENTATIONS
Page
OP–1
T. Bogdanov, E. Benova
Theoretical investigation of coaxial discharge based on 1d fluid model
47
OP–2
P. Marinova, M. Atanasova,
E. Benova
Reaction kinetics, heavy particles and rate
coefficients in HF and MW discharges in
argon at atmospheric pressure
48
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
Page
Measurements of nonlinear susceptibility 49
of multicomponent glassy matrix
processing by using femto second z-scan
method
OP–3
G. Yankov and E. Iordanova
OP–4
S Karatodorov, V Mihailov and
M Grozeva
Optical emission spectroscopy of plasma
produced by laser ablation of ferrous sulfide
49
OP–5
A. Kuzminova, J. Hanus,
A. Shelemin, O. Kylian and
H. Biederman
Fabrication of metal oxide nanoparticles
using gas aggregation source combined
with auxiliary oxygen RF plasma
50
OP–6
A. Kovalenko, J. Honová, M. Vala,
S. Luňák, L. Fekete,
I. Kratochvílová, P. Horáková,
L. Dokládalová, L. Kubáč and
M. Weiter
Gradual annealing effect and thermal stability of bulk-heterojunction solar cells
using DPP(TBFu)2 derivatives as donor
materials
51
OP–7
G. Alexiou, G. Tsigaras,
A. Kalampounias, E. Amanatides,
D. Mataras
Detection of power formation in SiH4/H2
glow discharge
52
OP–8
B. S. Blagoev, D. Z. Dimitrov,
V. B. Mehandzhiev, J. B. Leclercq,
P. K. Sveshtarov
Resistivity in Al doped ZnO nanolayers
obtained by atomic layer deposition
53
OP–9
V.E. Vrakatseli, E. Amanatides and
D. Mataras
Comparative study of RF reactive magnetron sputtering and SOL-GEL deposition
of UV induced superhydrophilic TiOx
thin films
54
OP–10
A.A. Ayrapetov, L.B. Begrambekov Stand for coating deposition and coatA.E. Evsin, A.V. Grunin,
ing/material testing
A.A. Gordeev, A.M. Zakharov,
A.M. Kalachev, Ya.A. Sadovskiy,
P.A. Shigin
55
OP–11
V. Sauchyn, I. Khvedchyn
Investigation of arc spot motion along the
electrodes in a plasma torch
56
OP–12
S. Boyadjiev, V. Georgieva and
I. M. Szilágyi
WO3 nanoparticles and WO3/TiO2 coreshell nanocomposites prepared by annealing and atomic layer deposition (ALD)
for gas sensing, photocatalytic and electrochromic applications
57
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
12
POSTER SESSION A:
PLASMA-SURFACE INTERACTION AND PLASMA DIAGNOSTICS.
MODELING AND COMPUTER SIMULATION
Page
Investigation of the hydrogen neutrals
61
in discharge source used for production
of metal hydrides
PA–1
I. Bozhinova, S. Iordanova,
A. Pashov
PA–2
A. Georgiev, A. Pashov,
D. Michailova, St. Zapryanov and
A. Blagoev
A study of sputtered tungsten atoms by
laser induced fluorescence
61
PA–3
V. Mihailov, S. Karatodorov and
O. Ivanov
Laser ablation threshold determination
by surface photo-charge effect
62
PA–4
V. Tankova, K. Blagoev,
M. Grozeva, G. Malcheva
Qualitative and quantitative laserinduced breakdown spectroscopy of
bronze objects
62
PA–5
D. Yordanova, G. Malcheva,
V. Tankova, A. Pirovska,
M. Grozeva
LIBS analysis of valuable precious metal museum objects
63
PA–6
M. Stefanova, P. Pramatarov,
A. Saifutdinov and A. Kudryavtsev
Identification of metal samples by collisional electron spectroscopy (CES)
63
PA–7
S. I. Slaveeva, T. P. Chernogorova,
K. A. Temelkov
Determination of spatially- and timeresolved electron temperature in nanosecond pulsed longitudinal discharge
64
PA–8
K. A. Temelkov, S. I. Slaveeva and
Yu. I. Fedchenko
Theoretical study on thermal conductivity of various gas mixtures through generalized Lennard-Jones interaction potential for application in gas-discharge
lasers
65
PA–9
M. Mitov, V. Videkov, Tsv. Popov, Investigation of parameters of gas disK. Raykov, A. Bankova
charge in an argon-oxygen mixture for
optimization of the growth of oxide
films
66
PA–10
D. López-Bruna, Tsv. Popov,
E. de la Cal
Monte Carlo estimates of edge particle
sources in TJ-II plasmas
67
PA–11
A. Kasilov, L. Grigor’eva,
V. Chechkin, A. Beletskii,
R. Pavlichenko, A. Lozin,
M. Kozulya, N. Zamanov,
Y. Mironov, V. Voitsenya
Peripheral plasma characteristics in the
URAGAN-3M torsatron
68
PA–12
M. Dimitrova, N. Puac, N. Skoro,
K. Spasic, G. Malovic, Tsv. Popov,
F. Dias, Z. Lj. Petrovic
Radial profile of the electron energy
distribution function in RF capacitive
gas discharge plasma
69
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
Page
Power flux density in the divertor re69
gion of the COMPASS tokamak in ohmic ELMy H-modes
PA–13
M. Dimitrova, V. Weinzettl,
J. Matejicek, Tsv. Popov,
S. Marinov, S. Costea, R. Dejarnac,
J. Stöckel, J. Havlicek and
R. Panek and the COMPASS team
PA–14
M. Dimitrova, E. Hasan,
P. Ivanova, E. Vasileva,
Tsv. Popov, R. Dejarnac, J.
Stöckel, P. Junek and R. Panek and
the COMPASS team
Electron energy distribution function in
the divertor region of the COMPASS
tokamak
70
PA–15
P. Ivanova, M. Dimitrova,
Tsv. K. Popov, D. López-Bruna,
P. Vondráček, R. Dejarnac,
J. Stöckel, M. Aftanas, P. Böhm,
P. Bílková, P. Junek, M. Hron and
R. Panek and the COMPASS team
Radial profile of the plasma parameters
measured by horizontal reciprocating
Langmuir probes in the COMPASS tokamak
71
PA–16
M. Damyanova, S. Sabchevski,
I. Zhelyazkov, E. Vasileva,
E. Balabanova, P. Dankov,
P. Malinov
Development of problem-oriented software packages for numerical studies
and computer aided design (CAD) of
gyrotrons
72
PA–17
M. Damyanova, U. Hohm,
E. Balabanova, D. Barton
Thermophysical properties of CF4/O2
and SF6/O2 gas mixtures
73
PA–18
I. Asenova and E. Valcheva
Intersubband optical absorption in nitride superlattice grown by MBE
74
PA–19
E. Koleva, V. Dzharov,
M. Kardjiev, G. Mladenov
Automation of the electron beam welding process
74
PA–20
E. Koleva, L. Koleva, D. Todorov,
G. Mladenov
Electron beam characterization by tomographic approach
75
PA–21
I.P.Levchuk, V.I.Maslov,
I.N.Onishchenko, A.M.Yegorov,
V.B.Yuferov
Vertical plasma turbulence suppression
in crossed electrcal and magnetic fields
due to finite lifetime of electrons and
ions and due to finite system length
76
PA–22
I.P. Levchuk, V.I. Maslov,
I.N. Onishchenko
Providing homogeneous and identical
focusing of train of short relativistic
electron bunches by Wakefield plasma
lens
77
PA–23
M. Nikovski, Zh. Kiss'ovski,
E. Tatarova
Model of surface-wave discharge with
fixed profile of gas temperature
78
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
14
Page
78
PA–24
E. Taskova, E. Alipieva and
G. Todorov
Stray magnetic field influence on the
CPT resonance in a coated Rb vacuum
cell
PA–25
T. Gyergyek, J. Kovačič
A self-consistent one-dimensional multifluid model of the plasma-wall transition in the presence of two species of
negatively biased particles
79
PA–26
H. Nichev, M. Petrov,
K. Lovchinov, N. Tyutyundzhiev
Open DSS simulations of power fluctuations induced by a rooftop PV generator on a building LV electrical grid
80
POSTER SESSION B:
SURFACES AND THIN FILMS PROCESSING AND ANALYSIS
Page
83
PB–1
S. Muhl, J. Cruz, J. Restrepo
Plasma induced heating of the substrate
during magnetron sputtering
PB–2
T. Nurgaliev, B. Blagoev,
V. Strbik, S. Chromik, M. Sojkova
Investigation of resistive properties of
HTS/manganite bi-layers
83
PB–3
V. Štrbík, Š. Beňačka, Š. Gaži,
M. Španková, V. Šmatko,
Š. Chromik, N. Gál, M. Sojková
and M. Pisarčík
Transport
properties
of
YBa2Cu3Ox/La0.67Sr0.33MnO3 nanojunctions
84
PB–4
M. Sojková, V. Štrbík,
Š. Chromik, M. Španková,
T. Nurgaliev, B. Blagoev
Fabrication of hybrid thin film structures
from HTS and CMR materials
85
PB–5
P.A. Atanasov, N.E. Stankova,
N.N. Nedyalkov,
T.R. Stoyanchov, Ru.G. Nikov,
N. Fukata, J.W. Gerlach,
D. Hirsch, B. Rauschenbach
Properties of nanosecond laser processed
polydimethylsiloxane (PDMS)
85
PB–6
G. Atanasova, N. Stoeva,
R. Nickolov, I. Spassova
Preparation and characterization of copper catalysts supported on mesoporous
silica-carbon nanocomposites
86
PB–7
A.Og. Dikovska, G.B. Atanasova,
G.V. Avdeev
Thin nanocrystalline zirconia films prepared by pulsed laser deposition
87
PB–8
A.Og. Dikovska, G.V. Avdeev,
G.B. Atanasova
Effect of Al2O3 on the low temperature
degradation of Y-PSZ thin films
87
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
Page
Investigation of the aging process of
88
noble metal nanostructures fabricated by
nanosecond laser ablation in water
PB–9
R.G. Nikov, A.S. Nikolov,
N.N. Nedyalkov, E.L. Pavlov,
P.A. Atanasov, M.T. Alexandrov,
D.B. Karashanova
PB–10
Ru.G. Nikov, N.N. Nedyalkov,
P.A. Atanasov
Laser nanostructuring of Ag films deposited on different substrates
89
PB–11
N. Nedyalkov, M. Koleva,
R. Nikov, Y. Nakajima,
A. Takami, M. Terakawa
Laser-induced optical properties changes
in gold doped materials
89
PB–12
N.E. Stankova, P.A. Atanasov,
Ru.G. Nikov, R.G. Nikov,
N.N. Nedyalkov
Laser-assisted processing of PDMS elastomer as a material for precise neural
interface engineering
90
PB–13
A. Nikolov, T. Koutzarova,
Study of barium hexaferrite nanostrucR. Nikov, N. Nedyalkov,
tures produced by laser ablation in water
N. Stankova, S. Kolev, P. Peneva,
D. Karashanova and D. Kovacheva
90
PB–14
A. Daskalova, C. Nathala,
W.Husinsky
Pump-probe investigation of femtosecond laser induced modification of biopolymer thin films
91
PB–15
A.A. Grechnikov, V.B. Georgieva,
N.Y. Donkov, A.S. Borodkov,
A.V.Pento, Tc.A.Yordanov
Comparison of different substrates for
laser-induced electron transfer desorption/ionization of metal complexes
92
PB–16
J. Walkowicz, V. Zavaleyev,
E. Dobruchowska, D. Murzynski,
A. Zykova, V. Safonov,
S.Yakovin, N. Donkov
Corrosion properties of zirconium-based
ceramic coatings for micro-bearing and
biomedical applications
93
PB–17
N. Donkov, A. Zykova,
V. Safonov, A.Goltsev,
T. Dubrava, I. Rossokha,
S. Yakovin, D. Kolesnikov,
I. Goncharov
Surface modification of tantalum pentoxide coatings deposited by magnetron
sputtering and further correlation with
cell adhesion and proliferation in in vitro
tests
94
PB–18
A. Bankova, V. Videkov,
K. Raykov, B. Tzaneva, M. Mitov
Investigation of the mechanical stability
of anodic aluminum oxide with vacuumdeposited thin metal film
95
PB–19
V. Donchev, M. Milanova,
J. Lemieux, N. Shtinkov,
I.G. Ivanov
Surface photovoltage and photoluminescence study of thick Ga(In)AsN layers
grown by liquid-phase epitaxy
96
PB–20
E. Halova, N. Kojuharova,
S Alexandrova, A Szekeres
Interface characterization of nanoscaled
SiOx layers grown on RF plasma hydrogenated silicon
97
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
16
Page
98
PB–21
A. Bencurova, K.Vutova,
A.Konecnikova, P.Nemec,
P. Hrkut, E.Koleva, I. Kostic,
G. Mladenov
Study of the CSAR62 new positive tone
electron beam resist at 40 keV electron
energy
PB–22
L. Nedelchev, D. Nazarova,
N. Berberova, G. Mateev,
V. Salgueiriño, D. Schmool
Enhanced photoanisotropic response in
azopolymer doped with elongated goethite nanoparticles
99
PB–23
N. Berberova, D. Nazarova,
L. Nedelchev, B. Blagoeva,
D. Kostadinova, V. Marinova,
E. Stoykova
Photoinduced variation of the Stokes
parameters of light passing through thin
films of azopolymer-based hybrid organic/inorganic materials
99
PB–24
M. Ormanova, V. Angelov,
P. Petrov
Investigation of thermal processes in
electron-beam surface modification by
means of a scanning electron beam
100
PB–25
S. Valkov, D. Dechev, N. Ivanov,
P. Petrov
Electron-beam induced surface alloying
of titanium with aluminium
101
PB–26
M. Berova, M. Sandulov,
T. Tsvetkova, D. Karashanova and
L. Bischoff
Structural modification of Ga+-ion implanted ta-C film
101
PB–27
M. Berova, M. Sandulov,
T. Tsvetkova and L. Bischoff
Vibrational spectroscopy of Ga+-ion implanted ta-C films
102
PB–28
D. Dimitrov, L. Komsalova,
D. Lilova, M. Sendova-Vassileva,
G. Popkirov , P. Vitanov,
I. Gadjov, M. Ganchev
Chemical bath deposition of TiN sulphide thin films
103
PB–29
S. Kaschieva, Ch. Angelov,
S.N. Dmitriev
MeV Electron Irradiation of Si-SiO2
Structures with Magnetron Sputtered
Oxide
104
PB–30
K. Raykov, V. Videkov,
A. Bankova
Wire bonding on vacuum deposited thin
metal film over nanostructured aluminum oxide
104
PB–31
K.T. Popov, V.G. Sears and
B.J. Jones
Gold distribution on latent fingermarks
developed by vacuum metal deposition
105
PB–32
T. Hristova-Vasileva, I. Bineva,
A. Dinescu, D. Nesheva,
D. Arsova, B. Pejova
Thickness influence on the morphology
and the sensing ability of thermally deposited tellurium films
106
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
POSTER SESSION C:
THIN FILMS DEPOSITION. COATINGS FOR ADVANCED APPLICATIONS
Page
Slow highly-charged ions transmission 109
through carbon nanomembranes and graphene
PC–1
R.A. Wilhelm, E. Gruber,
R. Heller, S. Facsko, F. Aumayr
PC–2
P.G. Sennikov, R.A. Kornev,
S.V. Golubev
PC–3
N. Lukat, E. von Wahl, H. Kersten Mass-spectrometry investigation
plasma for parylene C deposition
PC–4
Plasma-assisted CVD production of isotopes of group IV and VI elements in the
form of thin films, nanoparticles and
bulk material
110
of
111
D. Nicheva, V. Ilcheva,
T. Petkova, I. N. Mihailescu,
G. Popescu-Pelin, G. Socol,
C. Ristoscu, P. Petkov
Influence of the preparation method on
the optical properties of GeS1.2 – AgI
films
112
PC–5
I.I. Maronchuk, D.D. Sankovitch,
H. Nichev, D. DimovaMalinovska
Study of the morphology of Ge quantum
dots grown by liquid phase epitaxy
112
PC–6
H. Nichev, N. Georgiev,
M. Petrov, K. Lovchinov,
D .Dimova-Malinovska,
V. Bojinov
Arenecarboximide derivatives as dyesensitizers applied in thin film solar cells
113
PC–7
Zh. Dimitrov, M. Nikovski,
Zh. Kiss'ovski
Deposition of carbon nanostructures on
metal substrates at atmospheric pressure
114
PC–8
G. Georgieva, D. Dimov, M. Vala, Vacuum deposited organic solar cell
M. Weiter, G. Dobrikov, and
structures
I. Zhivkov
114
PC–9
T. Nurgaliev, E. Mateev,
Magnetron sputtering of Fe-oxide magL. Slavov, B. Blagoev, G. Gajda, netic films on dielectric and superconI. Nedkov
ducting substrates
115
PC–10
I. Hilmi, E. Thelander,
Ph. Schumacher, J. W. Gerlach,
B. Rauschenbach
Influence of the pulsed laser deposition
parameters on the properties of epitaxial
GST films on Si(111)
116
PC–11
T. Ivanova, A. Harizanova,
A. Petrova
Morphological and optical investigation
of Sol-Gel ZnO films
117
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
18
Page
118
PC–12
T. Ivanova, A. Harizanova,
T. Koutzarova, B. Vertruyen
Synthesis and properties of ZnO:Al thin
films prepared by SOL-GEL method
PC–13
R. Andreeva, E. Stoyanova,
A. Tsanev, D. Stoychev
Influence of the surface pretreatment of
aluminium on the processes of formation
of cerium oxides protective films
119
PC–14
N.I. Balalykin, J. Huran,
M.A. Nozdrin, A.A. Feshchenko,
A.P. Kobzev, V. Sasinková
Transmission photocathodes based on
stainless steel mesh and quartz glass
coated with N doped DLC thin films
prepared by reactive magnetron sputtering
120
PC–15
S. Gozzinia, A. Lucchesinia,
C. Marinellia, L. Marmugi,
S. Gateva, S. Tsvetkov,
S. Cartaleva
Transformation of electromagnetically
induced transparency into absorption in
thermal K optical cell with spin preserving coating
121
PC–16
L. Duta, G.E. Stan,
M. Anastasescu, H. Stroescu,
M. Gartner, Zs. Fogarassy,
N. Mihailescu, C. Luculescu,
S. Bakalova, A. Szekeres,
I.N. Mihailescu
Structural, optical and vibrational properties of nanostructured aluminum nitride
films synthesized by multi-stage pulsed
laser deposition
122
PC–17
M. Duta, J. Calderon-Moreno,
Electrical properties of p-type In-N coS. Preda, P. Osiceanu, S. Mihaiu,
doped ZnO thin films deposited on difM. Zaharescu, M. Gartner, S.
ferent substrates
Simeonov, D. Spasov, A. Szekeres
123
PC–18
D. Stoyanova, S. Kitova,
J. Dikova, M. Kandinska,
A.Vasilev, I. Zhivkov,
A. Kovalenko
Impact of the active layer nanomorphology on the efficiency of organic
solar cells based on a squaraine dye as a
donor
124
PC–19
M. Sendova-Vassileva,
G. Popkirov, P. Vitanov,
G. Grancharov, V. Gancheva,
H. Dikov, E. Lazarova
Optimization of the series resistance in
bulk heterojunction polymer solar sells
125
PC–20
Ch. Dikov, P. Vitanov, T. Ivanova
Optical and electrical properties of nanolaminate dielectric structures
125
Theoretical study of surface-wavedischarges in vacuum–plasma and dielectric–plasma configurations
127
POST DEADLINE CONTRIBUTION
PA–27
K. Ivanov, T. Bogdanov,
E. Benova
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
TL–3
CONTROL OF MICRO- AND
NANOSTRUCTURES IN TRANSITION
METAL NITRIDES: RECENT ADVANCES
Ivan Petrov
TOPIC LECTURES
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
21
TL–1
TAILORING SURFACE PROPERTIES OF DELICATE MATERIALS BY NEUTRAL
REACTIVE PLASMA SPECIES
M. Mozetič
Department of Surface Engineering, Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana,
Slovenia
Non-equilibrium gaseous plasma contains a variety of charged as well as neutral reactive particles. Their concentration depends on the production and loss rates. The production is often predominantly by electron impact – electrons from the high energy tail of the distribution function
are capable of ionizing, dissociating and exciting gaseous molecules. The production therefore
depends on the electron density and temperature. The loss rate of reactive particles in plasma at
low pressure is often by surface reactions. The probability for such reactions depends on the
type of particles and material facing plasma. Positively charged ions are accelerated across the
sheath next to the surface, lose at least a fraction of their kinetic energy upon impinging on the
surface so they cannot re-enter the gas phase. The probability for surface neutralization of positive ions is thus close to unity. Neutral reactive particles do not feel an electric force so they
can be trapped on the surface only providing a rather strong chemical bond is established upon
interaction with a solid material. Different materials exhibit different affinity to bond neutral
particles so the surface loss depends on the type of the material. Of particular interest are radicals, such as molecular fragments including neutral atoms. These particles will interact extensively with materials capable of chemisorbing atoms but will be just reflected from the surface
providing no suitable anchor site is available. The first types of materials are called catalysts
while the others are inert. The density of molecular fragments including neutral atoms in the
gaseous plasma therefore depends on the surface reactions rather than on the electron density
and temperature. Obviously, the flux of neutral reactive particles onto the surface of a treated
object immersed into gaseous plasma could be adjusted by placing a material of selected catalytic property next to the object. An alternative is treatment of the objects in the flowing afterglow where the charged particles are absent.
Tailoring the concentration of neutral radicals by selective catalysts allows for a functionalization of materials by specific functional groups. A high concentration of such functional groups
is unstable so they may decay quickly if a material is exposed to plasma itself. In order to avoid
this unwanted effect the materials are rather exposed to plasma afterglows. Such a treatment
allows for an optimal functionalization of polymer materials without side-effects otherwise
likely to occur upon treatment of polymers by gaseous plasma. Several examples of application
of in bio-medicine will be presented.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
22
TL–2
ION-BEAM ASSISTED DEPOSITION OF THIN FILMS
J.W. Gerlach
Leibniz Institute of Surface Modification (IOM),
Permoserstrasse 15, D-04318 Leipzig, Germany
In modern human life thin and ultrathin films play a tremendous role, a fact, which is in many
cases unbeknownst to the person using them. For the deposition of such films, which possess
highly specific properties and functionalities, a variety of different physical and chemical vapor
phase techniques is available. Ion-beam-assisted deposition (IBAD) is an effective physical
vapor deposition technique. It provides manifold possibilities to intentionally modify or determine the physical properties of the prepared thin films. The technique is characterized by the
simultaneous bombardment of the growing thin film with energetic ions during the deposition
process. The typical ion energies used with IBAD range from several 10 eV to several 10 keV.
Apart from the preparation of pure single elemental films (using noble gas ion bombardment),
IBAD is particularly well suited for the deposition of compound thin films (e.g. nitrides,
oxides) by using reactive gas ions (e.g. nitrogen, oxygen). This stems from the separation and
the resulting good controllability of the different particle fluxes being involved in the film
growth process. Furthermore, the technique allows for the application of in situ analysis methods in order to investigate the growth process in detail.
In this lecture, a short overview of the IBAD technique is given. Principles and basics of the
technique are addressed. Typical components of an IBAD system are presented and the most
prominent process parameters are related to them. The ion bombardment induced effects at and
below the sample surface are explained. Special weight is put into the dependence of the different ion bombardment induced processes on the ion energy. The requirements in order to deposit high quality epitaxial thin films by IBAD are explained as well. All explanations are illustrated by results obtained from IBAD films. The lecture closes with a short outlook on future
developments of the IBAD technique.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
23
TL–3
CONTROL OF MICRO- AND NANOSTRUCTURES IN TRANSITION METAL
NITRIDES: RECENT ADVANCES
Ivan Petrov
Frederick Seitz Materials Research Laboratory and Materials Science Department, University
of Illinois, Urbana, Illinois 61801
Department of Physics (IFM), Linköping University, SE-581 83 Linköping, Sweden
petrov@illinois.edu
Polycrystalline TiN and related transition-metal nitride (TMN) thin films are typically deposited by reactive magnetron sputter deposition and employed as diffusion barriers in microelectronics as well as hard, wear-, and corrosion-resistant coatings in mechanical and optical
applications. We use a combination of HR-XRD, TEM, HR-XTEM, AFM, and STM analyses
to characterize micro- and nanostructures. We will review the fundamental film growth processes - nucleation, coalescence, competitive growth, and recrystallization - and their role in thin
film microstructure evolution as a function of substrate temperature. Special attention will paid
to in-situ substrate treatment by ion-irradiation and its effect on film microstructure and adhesion. Using spontaneous natural patterning processes, we show that self-organized nanostructures consisting of commensurate nanolamellae, nanocolumns, nanospheres, and nanopipes can
be synthesized to further extend the range of achievable properties. All of these structures are a
result of kinetic limitations and require low growth temperatures combined with low-energy
(less than the lattice atom displacement potential), very high flux, ion irradiation during deposition. We will also review recent advances in the selective use of metal ions during HIPIMS cosputtering to extend the attainable structures and properties in metastable TMN with examples
of Ti(1-x)AlxN, Ti(1-x)SixN, ad Ti(1-x)TaxN. We probe the effects of (i) metal versus rare-gas ion
irradiation as well as (ii) the type of metal ion uses (Ti vs Me). We employ a metastable NaClstructure Ti0.39Al0.61N as a model system to demonstrate that switching from Ar+- to Al+dominated bombardment eliminates phase separation, minimizes renucleation during growth,
reduces the high concentration of residual point defects, and thus results in dense, single-phase,
stress-free films.1
For metastable alloys, TiAlN and TiSiN, mechanical properties are shown to be determined by the average metal-ion momentum transfer per deposited atom
.2 Irradiation with
lighter metal-ion (Me = Al+ or Si+ during Me-HIPIMS/Ti-DCMS) procures fully-dense singlephase cubic Ti1-x(Me)xN films.3 In contrast, with higher-mass film constituents such as Ti,
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
24
easily exceeds the threshold necessary for phase segregation which results in precipitation of
second w-AlN or Si3N4 phases.
With the TiTaN system we show that synchronized pulsed ion bombardment in the hybrid system with the heavy-metal ions (Ta) permits to grow dense, hard, smooth, and stressfree thin films at lowered substrate temperature, with no external heating.4
Overall, we demonstrate that using synchronous bias to select the metal-rich portion of
the ion flux opens new dimension for ion-assisted growth in which momentum can be tuned by
selection of the metal ion in the hybrid/cosputtering configuration and stresses can be eliminated/reduced since the metal ion is a component of the film.
1
G. Greczynski, J. Lu, M. Johansson, J. Jensen, I. Petrov, J.E. Greene, and L. Hultman, Vacuum 86 (2012) 1036
2
G. Greczynski, J. Lu, J. Jensen, I. Petrov, J.E. Greene, S. Bolz, W. Kölker, Ch. Schiffers, O.
Lemmer and L. Hultman, JVSTA 30 (2012) 061504-1
3
G. Greczynski, J. Lu, J. Jensen, I. Petrov, J.E. Greene, et al, Thin Solid Films, 556 (2014) 87
4
G. Greczynski, J. Lu, I. Petrov, J.E. Greene, S. Bolz, W. Kölker, Ch. Schiffers, O. Lemmer
and L. Hultman, JVSTA 32 (2014) 041515
TL–4
MESOSCOPIC METHODS AS A TOOL TO DESCRIBE AND INTERPRET SURFACE
PHENOMENA
Vasco Guerra
Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa
1049-001 Lisboa, Portugal
This work addresses the question of modelling heterogeneous molecule formation on silica or
Pyrex surfaces. Despite the impressive evolution of semi-classical molecular dynamics calculations in recent years [1,2], its application to realistic conditions of molecule formation on silica
surfaces is still difficult. Moreover, the direct coupling with complex gas-phase chemistry
models remains unpractical. In this context, “coarse-grained” mesoscopic models describing
the surface in terms of fractional coverages of different adsorption sites, albeit the lack of a true
predictive capacity, continue to form powerful tools to describe and interpret surface phenomena.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
25
Two complementary approaches are explored. The first one relies on a deterministic description where the time-evolution of the adsorbed species and adsorption sites is ruled by a system
of reaction-rate differential equations associated with different elementary processes [3,4]. The
second one is to use a stochastic dynamical Monte Carlo scheme, as outlined in [5,6].
The formation of NO2 molecules on a Pyrex tube of inner radius 1 cm, as a result of NO oxidation by previously adsorbed O atoms on the wall [7,8] is taken as a case study, but other systems are investigated as well. It is shown that dynamical Monte Carlo methods, in particular
with an algorithm based on local update with lists, can be effectively used to simulate surface
kinetics and coupled gas phase and surface chemistries. These methods are particularly suited
to studying systems where surface diffusion of physisorbed atoms and/or molecules plays an
important role.
Acknowledgments
This work was partially funded by Portuguese FCT – Fundação para a Ciência e Tecnologia,
under Project UID/FIS/50010/2013.
References
[1] M. Rutigliano, C. Zazza, N. Sanna, A. Pieretti, G. Mancini, V. Barone and M. Cacciatore,
J. Phys. Chem. A 113 (2009) 15366–75.
[2] A. Bogaerts, M. Eckert, M. Mao and E. Neyts, J. Phys. D: Appl. Phys. 44 (2011) 174030.
[3] B.F. Gordiets and C.M. Ferreira, AIAA J. 36 (1998) 1643–51.
[4] V. Guerra, IEEE Trans. Plasma Sci. 35 (2007) 1397–412.
[5] K.A. Fichthorn and W.H. Weinberg, Chem. Phys. 95 (1991) 1090–6.
[6] V. Guerra J. Loureiro, Plasma Sources Sci. Technol. 13 (2004) 85–94.
[7] O. Guaitella, M. Hübner, S. Welzel, D. Marinov, J. Röpcke and A. Rousseau, Plasma
Sources Sci. Technol. 19 (2010) 45026.
[8] V. Guerra, D. Marinov, O.Guaitella and A. Rousseau, J. Phys. D: Appl. Phys. 47 (2014)
224012.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
26
TL–5
NON-CONVENTIONAL PLASMA AND SHEATH DIAGNOSTICS
H. Kersten, S. Bornoldt, A. Spethmann, V. Schneider, T. Trottenberg
Institute for Experimental and Applied Physics, University of Kiel, Kiel, Germany
In addition to well-established plasma diagnostic methods (Langmuir probes, optical emission
spectroscopy, mass spectrometry etc.) we perform examples of “non-conventional” diagnostics
[1] which are applicable to technological plasma processes for particle formation, surface
structuring and thin film deposition:
i) The total energy influx from plasma to substrates can be measured by special calorimetric
probes (passive or active, respectively) as well as by fluorescent micro-particles. Examples for
rf-discharge and magnetron sputtering will be provided [2-5]. By comparison with model
assumptions on the involved plasma-surface mechanisms, the different contributions to the
total energy influx can be separated.
ii) For a variety of thin film applications it is essential to determine the sputtering yield as well
as the angular distribution of sputtered atoms. For this purpose we developed a novel and rather
simple method, the so-called sputtering-propelled instrument (SPIN) [6]. It is stack nearly
without friction and exposed to a vertical ion beam, rotating due to momentum transfer by the
released particles, i.e. sputtered target atoms and reflected ions. Comparison of the
measurements with simulation yields valuable information on the sputtering mechanisms and
support validation of related sputter codes. The angular distribution of sputtered particles was
also measured by a sensitive pendulum which is commonly used for thrust measurements in
ion beam sources for space propulsion systems.
REFERENCES:
[1] T. Trottenberg et.al., Plasma Phys. Control Fusion 54(2012) 124005.
[2] H. Maurer, H. Kersten, J. Phys. D: Appl. Phys. 44(2011) 174029.
[3] I. Levchenko, M. Keidar, S. Xu, H. Kersten, K. Ostrikov, JVSTB 31(2013) 050801.
[4] K. Nishiyama et.al., J. Nucl. Mat. 438(2013), S788-S791.
[5] H. Kersten, H. Deutsch, H. Steffen, et.al., Vacuum 63(2001) 385-431.
[6] J. Rutscher T. Trottenberg, H. Kersten, Nucl. Instr. Meth. Phys. Res. B 301(2013) 47-52.
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
PR–9
STRUCTURING ON A NANOSCALE TO
MANUFACTURING HARD THIN FILMS
Naureen Ghafoor
PROGRESS REPORTS
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
29
PR–1
RECENT RESULTS IN EDGE PLASMA STUDIES ON THE COMPASS
TOKAMAK
R. Panek, J. Adamek, P. Bilkova, P. Cahyna, R. Dejarnac, M. Dimitrova, P. Hacek,
J. Havlicek, M. Hron, M. Imrisek, M. Komm, T. Markovic, M. Peterka, J. Seidl, J. Stockel,
P. Vondracek, V. Weinzettl and the COMPASS team
Institute of Plasma Physics AS CR, Prague, Czech Republic
COMPASS is a compact tokamak (R = 0.56 m, a = 0.2 m) operated in divertor plasma configuration with an ITER-like plasma cross-section. COMPASS operates with a plasma current of
up to 0.4 MA and a toroidal magnetic field in the range of 0.9 – 2.1 T. It has been equipped by
two new neutral beam injectors, which provide power of 2 × 0.4 MW at the beam energy of 40
keV for additional plasma heating and which enable co- or balanced injection. COMPASS operates in an ohmic as well as NBI assisted H-mode accompanied by Type-I and Type-III Edge
Localized Modes (ELMs) in the frequency range of 80 – 1 000 Hz.
The main focus of the COMPASS scientific program is on the edge, SOL and divertor
physics supported by a comprehensive new diagnostic system. Characterization of H-mode and
ELMs using several newly developed diagnostic techniques, which allow for unique measurements of the plasma parameters in the pedestal, SOL and divertor regions, will be shown.
In addition, COMPASS is equipped with a system of coils for generation of magnetic perturbations (MP) with a toroidal mode number of n = 2. The plasma response to applied magnetic
perturbation in L- and H-mode by 100 diagnostic saddle loops covering the whole vacuum vessel will be presented. In addition, the changes in divertor plasma during the application of MP
will be shown.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
30
PR–2
Li-BEAM DIAGNOSTIC SYSTEM FOR THE COMPASS TOKAMAK
M. Berta1,2,3
G. Anda , A. Bencze , D. Dunai , P. Hacek3, J. Krbec3, R. Panek3, G. Veres2, S. Zoletnik2
2
2
2
Széchenyi István University, Győr, Hungary
2
Wigner RCP, Budapest, Hungary
3
Institute of Plasma Physics CAS, v.v.i., Prague, Czech Republic
1
Detailed information about the electron density profile and its fluctuations is very valuable and
important for operation of tokamaks. Li-beam diagnostic method is one of the useful
techniques of electron density measurement.
The COMPASS tokamak is equipped with a completely new Li-beam diagnostic system, which
has been extended with a novel Li-ion detector for plasma edge current fluctuation
measurement.
The energy of the incident beam can be varied from 10 − 120 keV. The ion current extracted
from the emitter is between 1 − 5 mA. The observation system has three branches.
At the bottom of the machine is placed an 18-channel, radially distributed system of avalanche
photodiodes with appropriate optics for fast profile and fluctuation measurement.
On the top of the COMPASS tokamak there is a CCD camera installed for slow density profile
measurements, and an ion detector − called atomic beam probe − for plasma edge current
fluctuation measurements.
With this system we are able to reconstruct the electron density profile every 4 microsecond
with 1 − 2 cm spatial resolution. The density fluctuations dynamics can be followed with a
time resolution of 500 nanosecond. The ion detection system is in test operation, but its
expected time resolution is about 10 − 20 μs, the spatial resolution is in the submillimeter
range, and will be able to resolve 10% of the edge plasma current's changes.
Besides of the diagnostic system's description, experimental results demonstrating the system's
capabilities will also be presented.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
31
PR–3
HEAT LOADS ON TUNGSTEN DIVERTOR TARGETS IN ITER
J. P. Gunn
CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France.
The International Thermonuclear Experimental Reactor (ITER) will begin operation with a full
tungsten (W) divertor consisting of solid W monoblocks (MB) bonded to CuCrZr watercarrying cooling tubes. The "Heat and Nuclear Load Specifications" (HNLS) is the ITER
Project Level document that defines the maximum thermal loads to which plasma-facing components can be subjected, based on the best current knowledge from both physics modelling
and observations on current devices. The maximum manageable heat loads to the divertor are
imposed by engineering knowledge about material/technology limits, and validated by tests in
high heat flux devices. In steady state (SS), the maximum inter-ELM heat load allowed by the
HNLS is qHNLS = 10 MW/m2. During the lifetime of the first divertor, which is supposed to
survive until the end of the first full D-T campaign, slow transient (ST) re-attachment events
may occur due principally to loss of detachment control. During each of these events, the divertor can sustain qHNLS = 20 MW/m2 for up to 10 s. Concerning fast transients (FTs), e.g. edge
localized modes (ELMs), it is the surface heat flux factor which is of interest, because we wish
to compare it to the melting threshold of W, εmelt = 48 MJ/m2s1/2. The heat flux factor is given
by the energy flux density normal to the MB surface, divided by the square root of the FT rise
time ΔtELM = 250 µs.
All the heat loads described above are specified in the HNLS in terms of heat flux normal to an
ideal, axisymmetric, unshaped divertor surface, but MB shaping, potential misalignments, and
castellation lead inevitably to local heat flux peaking. The actual power flux delivered to any
point on the MB surface must be calculated by integrating the distribution functions at the
sheath entrance, modified to describe shadowing by surface features. Surface heat loads on
several ITER monoblock design options are derived using physics-based modelling. Power
flow into gaps, target tilting, and monoblock shaping would lead to peak temperatures that can
exceed the tunsgten recrystallization temperature during inter-ELM detached regime, and possible edge melting during slow transient reattachment. Furthermore, the margin against global
surface melting due to mitigated ELMs would be lost.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
32
PR–4
HIGH TIME-RESOLUTION OPTICAL INVESTIGATIONS OF PEO DISCHARGES:
TOWARDS A BETTER UNDERSTANDING OF WHAT IS GOING ON DURING
PLASMA ELECTROLYTIC OXIDATION OF LIGHT ALLOYS
G. Henrion1, A. Nominé2, S.C. Troughton3, J. Martin1, A.V. Nominé2, T.W. Clyne3, T.
Belmonte1
1
Institut Jean Lamour, CNRS – Université de Lorraine, Nancy, France
The Open University, Department of Physical Sciences, Milton Keynes, United Kingdom
3
Department of Materials Science & Metallurgy, Cambridge University, United Kingdom
2
The Plasma Electrolytic Oxidation (PEO) is a particular electrochemical process to produce
protective oxide ceramic coatings on light-weight metals as aluminium, magnesium or
titanium. The process is carried out in a liquid conductive electrolyte and high current density
(some 10s of A.dm-2) and voltage (some 100s of V) are applied to the working electrode. This
leads to the development of micro-discharges (MDs) on the sample surface due to dielectric
breakdown. It is admitted that MDs are the main contributors that allow oxidation to pursue
beyond the usual limits encountered in anodizing.
Although several investigations have been carried out to improve the efficiency of the PEO
process, and despite the considerable interest in this process, there is still no clear
understanding of the underlying discharge mechanisms that make possible metal oxidation up
to hundreds of µm through the ceramic layer. Indeed, these mechanisms are complex because
they occur in a multi-phase medium with multiple interphases.
Using optical tools with high time-resolution may help to characterize the MDs and therefore
propose descriptive breakdown mechanisms and resulting oxidation of the material.
After a brief review of the recent progress in PEO process investigation, the presentation will
focus on the latest results related to optical emission spectroscopy of PEO discharges together
with high-speed video imaging of single PEO discharges. It will particularly be shown that
discharges occur as cascades with duration of some tens of micro-seconds, and that successive
cascades tend to ignite at the same location over one half-cycle of the AC current. Another
issue that will be addressed concerns the mutual behavior of discharges and gas bubbles. Does
the discharge ignite in a gas bubble or is the bubble a consequence of the discharge ignition? In
fact, the question is still open and light may come from video images of both discharges and
bubbles.
In light of these results, the breakdown-growth mechanisms will be discussed by describing
both the physical behaviour of the plasmas and the growth of the oxide coating.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
33
PR–5
OES AND MASS SPECTROMETRY CHARACTERIZATION OF ATMOSPHERIC
PRESSURE PLASMA JETS
N. Puač, D. Maletić, N Selaković, G. Malović and Z.Lj. Petrović
Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
Fast time-resolved ICCD imaging is one of the easiest and, also, the most important ways to
investigate time/space development of plasma in plasma jet systems. From these high-speed
images, it can be seen that plasmas in plasma jets are not always continuous, but they sometimes appear as plasma packages that propagate from the glass tube filled with a flow of helium
into the surrounding atmosphere. These plasma packages, the so called “plasma bullets” or
PAPS (pulsed atmospheric pressure streamers), are not yet fully understood. It is assumed that
photons and Penning ionization play the main role in propagation of “plasma bullets”. We have
investigated PAPS development and propagation for various electrode set-ups [1, 2]. It was
shown that an optimal configuration can be found in order to get the maximum travelling distance of PAPS. Also, while inside the electrodes plasma has a ring-like shape and it is mainly
travelling along the walls of the glass tube. On the other hand, inside the glass tube (interelectrode region) plasma is confined to the center of the tube and the main emission is originating from that volume. When plasma comes in contact with the ambient air, the discharge volume increases and plasma acquires a sphere-like shape before its starts to travel in open air. At
all times, the PAPS are connected with the main discharge inside the tube with a trail of a very
small emission. Since the main reason for the development of these atmospheric plasma devices are applications, particularly in medicine and biology, it is necessary to make detailed
diagnostics of the plasma and, most importantly, examine its chemical composition. We have
used a Hiden HPR 60 mass-energy analyzer for the integrated and time-resolved measurements
of the neutral and ionic species originating from an atmospheric-pressure plasma jet.
Acknowledgments: This research has been supported by the Ministry of Education, Science
and Technological Development, Republic of Serbia, under projects III41011 and ON171037.
1. N Puač, D Maletić, S Lazović, G Malović, A Đorđević and Z Lj Petrović 2012 Appl. Phys.
Lett. 101 24103
2. D Maletić, N Puač, N Selaković, S Lazović, G Malović, A Đorđević and Z Lj Petrović
2015 Plasma Sources Sci. Technol. 24 025006 (9pp)
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
34
PR–6
ATMOSPHERIC PRESSURE PROCESSING WITH COLD RADIOFREQUENCY
PLASMA JETS
G. Dinescu1,2
1
National Institute for Laser, Plasma and Radiation Physics, Atomistilor 409, 077125,
Magurele- Bucharest, Romania
2
Physics Department, University of Bucharest, Atomistilor 405, Magurele, Romania
We present the principles and various discharge configurations for producing cold radiofrequency plasmas at atmospheric pressure, like plasma jet sources of DBD (Dielectric Barrier Discharges) and DBE type (Discharges with Bare Electrodes) and their utilization in engineering, biology and medicine, environment, and nanotechnology. The applicative potential of
those plasmas is exemplified with: polymer surface modification in order to control the wettability, cleaning and etching, patterning the cells growth on surface, promoting the adhesion of
dental prostheses, operation in liquid phase for chemical decomposition, functionalization of
carbon nanowalls, and synthesis of metallic nanoparticles.
PR–7
EFFECT OF DIFFERENT BIAS MODES ON STRUCTURE AND PROPERTIES OF
COATINGS AND DIFFUSION LAYERS PRODUCED BY CATHODIC ARC PVD
M. Ürgen1, S. Öncel2
1
Istanbul Technical University, Department of Metallurgical and Materials Engineering, 34469,
Maslak, Istanbul-Turkey
2
Nanomate Surface Tech Inc. DES San. Sit. 116. Str. No:22
34776 Y.Dudullu, Umraniye Istanbul
Cathodic arc plasmas are capable of highly ionizing the metal vapors created by the arcs
travelling on the cathode surface. Thus the plasmas created in this manner are rich in both
metal ions and electrons. In the conventional cathodic arc PVD (CAPVD) process, a negative
DC or pulse bias is applied to substrate surfaces for achieving a dense and very well adherent
coatings on the substrate.
In the first part of this presentation, the effects of the negative bias magnitude and mode
will be discussed. Specific examples will be given for TiN and TiAlN coatings produced by
using high-voltage pulse bias.
In the second part of the talk, a recent method developed in our group will be presented. In this
method, contrary to conventional applications, we aimed to utilize both the electrons and ions
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
35
in the CA plasma by the application of AC bias to the substrates. The method allows heating
the substrate in a controlled manner by tuning the electron current passing through the substrate. Thus it becomes possible to alloy the substrate with the depositing metal or alloy and to
minimize the stress in the hard coating. Several applications of the method related to surface
alloying (aluminizing of nickel, titanium and steel) and low stress nitride based coatings (TiN)
will be given and discussed.
PR–8
STRUCTURING ON A NANOSCALE TO MANUFACTURING HARD THIN FILMS
(From structural design to deformation mechanisms)
Naureen Ghafoor
naugh@ifm.liu.se
Nanostructured Materials, Department of Physics, Chemistry, and Biology (IFM), Linköping
University, SE-581 83 Linköping, Sweden
“Man is a tool-using animal...” − this statement has often been described in history to distinguish the technological abilities of humans from those of other creatures. Today, more than 2.5
million years after the earliest discovery of tools, tool technology still stays a decisive factor in
our evolution. Among the many factors that determine the functionality of a tool is its hardness. It is a fundamental property and may be the most crucial one. Thanks to the contemporary
progress in scientific methodology, today we are able to uncover the hardening mechanisms in
old known materials. This knowledge can be used to manufacture even harder materials, including very thin films deposited onto tools, for better cutting performance under harsh conditions.
In this lecture, a general concept of hardness in a few bulk materials will be reviewed with the
main focus on nanostructuring. Two-phase complex nanostructures from immiscible transition
metal nitrides Zr1-xAlxN 1 and Zr1-xSixN 2 alloys as well as Zr1-xAlxN/ZrN and Zr1-xSixN/ZrN superlattices were realized with a thin-film deposition technique called magnetron sputtering. The
growth, structure, and hardness relationship will be presented. We have explored a range of
obtainable self-organized structures in these materials. The phase evolution, decomposition,
and mechanical properties of the films as a function of the structural design and growth parameters will be discussed.
There will be an emphasis on the necessity to perform theoretical calculations and profound
structural characterization of the complex nanostructures in addition to the syntheses to develop future thin films for cutting tools.
1
N. Ghafoor, L. Johnson, D. Klenov, J. Demeulemeester, P. Desjardins, I. Petrov, L. Hultman, M. Odén, APL
Materials 1 (2) (2013) 022105.
2
N. Ghafoor, I. Petrov, D.O. Klenov, B. Freitag, J. Jensen, J.E. Greene, L. Hultman, M. Odén, Acta Materialia 82
(0) (2015) 179.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
36
PR–9
FROM AB-INITIO DESIGN TO SYNTHESIS OF MULTIFUNCTIONAL THIN FILM
COATINGS WITH ENHANCED HARDNESS AND TOUGHNESS
V. Chirita
Thin Film Physics, IFM, Linköping University, Sweden
Enhanced toughness in hard and superhard thin films is a primary requirement for present day
ceramic hard coatings, known to be prone to brittle failure during in-use conditions, in modern
applications. Density Functional Theory (DFT) investigations predicted significant improvements in the hardness/ductility ratio of several pseudobinary B1 NaCl structure transition-metal
nitride alloys, obtained by alloying TiN or VN with NbN, TaN, MoN and WN [1, 2]. The initial calculations reveal that the electronic mechanism responsible for toughness enhancement
stems from the high valence electron concentration (VEC) of these alloys, which, upon shearing, leads to the formation of alternating layers of high and low charge density oriented orthogonal to the applied stress, and ultimately allows a selective response to tetragonal and trigonal
deformations.
Recently, these results have been validated experimentally [3]. Single-crystal
V0.5Mo0.5N/MgO(001) alloys, grown by dual-target reactive magnetron sputtering together
with VN/MgO(001) and TiN/MgO(001) reference samples, exhibit hardness > 50 % higher
than that of VN, and while nanoindented VN and TiN reference samples suffer from severe
cracking, the V0.5Mo0.5N films do not crack. New DFT calculations address the issue of lattice
ordering effects on the mechanical properties of these pseudobinary alloys, and concentrate on
V0.5Mo0.5N, V0.5W0.5N, Ti0.5Mo0.5N and Ti0.5W0.5N alloys. The results reveal that while the degree of electronic structure layering, i.e. the formation of alternating layers of high and low
charge density upon shearing, becomes less pronounced in disordered configurations, the overall VEC effect is not affected. The essential feature in the disordered alloys, as initially reported for ordered alloys, is the increased occupancy of electronic d-t2g metallic states, which
allows the selective response to tensile/shearing stresses, and explains the enhanced toughness
confirmed experimentally for V0.5Mo0.5N films.
[1] D. G. Sangiovanni et. al. Phys. Rev. B 81, 104107 (2010).
[2] D. G. Sangiovanni et. al. Acta Mater. 59, 2121 (2011).
[3] H. Kindlund et. al, APL Materials 1, 042104 (2013).
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
37
PR–10
THREE APPROACHES TO PRODUCING APPLICATION TAILORED Me-CARBON
FILMS
Papken Eh. Hovsepian and Arutiun P. Ehiasarian
HIPIMS Technology Centre, Sheffield Hallam University, Howard Street, Sheffield, S1 1WB,
UK
The lecture discusses three approaches to producing metal carbon films to address triboological
problems in key industrial applications.
The first approach utilizes the effects of dynamic segregation and self-organization growth
mechanisms in Cr-C films to achieve high wear resistance. High ion irradiation during coating
growth of C-based coatings can produce clusters of almost pure carbon surrounded by a hard
Me-carbide phase. The clusters are arranged in a nanoscale multilayer structure with an abnormally large spacing between the individual layers of 25 nm. Cr-C films with carbon clusters
when used as a top coat on TiAlCrYN have shown excellent performance in dry machining of
Ni-based alloys.
The second approach utilizes the effect of low shear strength interfaces in nanoscale multilayer
structured V-C based films to control coating wear mechanism. In TiAlCN/VCN coatings carbon segregates laterally during the coating growth to produce a weak phase at the interface between the individual layers of TiAlCN and VCN. The low shear strength carbon based interfaces prevent built up edge formation when machining Al and Ti alloys.
The third approach utilizes tribochemical reactions to achieve low friction and high wear resistance of Me-C films in boundary lubrication and at elevated temperatures. Mo-W- C coatings
were deposited by a combined nonreactive HIPIMS and DC-sputtering technique. In pin-ondisc tests at room temperature lubricated conditions using non-formulated engine oil (Mobil1
10W-60), the coatings showed a friction coefficient of µ = 0.033, which was lower than that
reported for a number of DLCs. At 200oC and lubricated conditions, the friction coefficient
remained low at 0.05 compared to 0.08 measured for state-of-the-art DLC coating under the
same conditions. Raman spectroscopy of the wear debris revealed that in lubricated conditions
the wear product contained a MoS2 phase. In boundary lubrication condition, the friction behavior of the Mo-W doped C coatings is influenced by the formation of solid lubricants via tribochemical reactions at the asperity contacts due to high flash temperatures. Mo-W-C films are
potential candidates to prolong the life time of automotive components.
38
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
PR–11
FRACTAL VS RANDOM FIELD CHARACTERIZATION OF COMPLEX
MORPHOLOGIES AND PATTERNS
Oleg I. Yordanov
Institute of Electronics, Bulgarian Academy of Sciences. 72 Tsarigradsko Chaussee blvd, Sofia
1784, Bulgaria
Fractal methods, and their generalization multifractal methods, are becoming increasingly
popular for characterization of complex structures in a variety of science and technology areas.
An important example is provided by the surface roughness, which in turn affects a number of
physical processes. The fractals own their du jour to the simplicity of methods as well as to the
availability of algorithms and software for evaluation of the fractal dimension(s). A number of
drawbacks exist, however, which substantially limit the applicability and the usefulness of the
fractal models. The most serious one is related to the interpretation of the results: the fractal
estimation provides just values of exponent(s)/dimension(s), evidence (sometimes rather poor)
of a scaling, which is hard to link with relevant physical characteristics and processes. Another
major problem comes from the lack of methods for statistical validation of the results obtained
rooted in the fact that the probability distributions of the fractal dimensions is almost never
known.
In this report, we review the development and present some new results for an alternative approach based on modelling of complex patterns using approximate scale-invariant random
fields [1,2]. The fields of interest are constructed from their spectral (Fourier) representations
and involve single- or multi-segment, power-law, piece-wise continuous functions. In contrast
to the fractal methods, the stochastic field modelling renders a richer and more adequate description of the complex structures, including variances, autocovariance and structures functions, root mean derivatives, curvature, etc. A particular focus in the report is given to the statistical estimations of these functions from empirical data as well as to the computer simulations of the fitted fields. Both represent new facets of the methodology and are key steps for the
models’ statistical verification.
[1] Yordanov O.I. and N.I. Nickolaev, Phys. Rev. E, (Rapid Comm.), 49, p. R2517 (1994).
[2] O. Yordanov and I. Atanasov, European Phys. Jour. B, 29, p. 211 (2002).
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
39
PR–12
LOCAL EPITAXIAL GROWTH EFFECT IN REACTIVELY SPUTTERED OXIDE
THIN FILMS
J.F. Pierson1, Y. Wong1, J. Ghanbaja1, F. Soldera2, D. Horwat1, F. Mücklich2
1
2
Institut Jean Lamour, Université de Lorraine, Nancy, France
Department for Materials Science, Saarland University, Saarbrücken, Germany
The texture of thin films strongly influences their functional properties (hardness, oxidation
resistance, electrical resistivity, optical properties…). In reactively sputtered thin films, the
texture of the coatings can be tuned by the deposition conditions, such as bias voltage, total
pressure, reactive gas flow rate… However, the deposition parameter window to get a specific
texture can be narrow and during the synthesis of the coating a small change in the conditions
may induce a drastic change of the film texture. In this presentation, the Cu-O and Ni-O
systems are studied to show their ability to grow at room temperature and on glass substrates
oxide films with a texture that is independent on the deposition conditions.
Among the various deposition conditions, the total pressure is found to have a strong effect on
the preferred orientation of Cu2O films: [100] at a low pressure and [111] at a high pressure [1].
Using a two-step deposition procedure, a highly textured Cu2O thin film with a controlled
orientation can be formed independently of the deposition conditions. Provided that it has a
sufficient thickness, this layer acts as a seed layer that determines the crystal orientation of a
second layer grown even after air exposure and/or without specific cleaning of the surface prior
to deposition [2]. High-resolution transmission electron microscopy analyses evidence that the
top layer grows in homoepitaxy with the seed layer with a microstructure consisting of single
crystal columns crossing the interface between the layers. The same behavior has been
obtained for NiO thin films. Finally, this local epitaxial growth effect has been used to grow
NiO films with [111] texture on a previously deposited Cu2O film [3].
[1] Y. Wang et al., Appl. Surf. Sci. 335 (2015) 85
[2] Y. Wang et al., Acta Mater. 76 (2014) 207
[3] Y. Wang et al., submitted
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
40
PR–13
SURFACE INTERACTIONS OF PLASMA-GENERATED SPECIES
M.A. Gleeson1, T, Zahria2, A.W. Kleyn3, and M.C.M van de Sanden1
1
Dutch Institute for Fundamental Energy Research (DIFFER), De Zaale 20, 5612 AJ,
Eindhoven, The Netherlands.
2
Materials Innovation Institute (M2i), P.O. Box 5008, 2600 GA Delft, The Netherlands.
3
Center of Interface Dynamics for Sustainability, Chengdu Development Center for Science
and Technology, 355, Tengfei Er Road, Chengdu, Sichuan 610207, People’s Republic of China.
This progress report presents recent developments in plasma-materials interaction research at
the Dutch Institute for Fundamental Energy Research (DIFFER). The work is primarily
focussed on plasma-surface interactions and the utilization of UHV techniques to investigate
the same.
The plasma state can produce reactive or activated species that can drive unconventional
reactions and reduce barriers to chemical conversions that may be high under conventional
chemical conditions. However, the plasma is a complex environment and disentangling the
significance of the contribution from various processes is extremely challenging.
To circumvent this, an approach is adopted that separates plasma generation from the surface
interaction. This is illustrated by presenting a recent work on the interaction of hyper-thermal
nitrogen with ruthenium [1], which produced a clear-cut demonstration of Eley-Rideal (ER)
(direct abstraction) reaction for a “heavy atom” system. The evidence for ER reaction along
with the details it reveals about the reaction system are discussed.
We will also give an introduction to recently initiated projects on the role that surfaces and
materials can play in realizing plasma-assisted conversion of CO2 for the purpose of solar fuels
production. This work is part of a core line of research at the DIFFER institute.
[1] “Eley-Rideal Reactions with N Atoms at Ru(0001): Formation of NO and N2”, Teodor
Zaharia, Aart W. Kleyn, and Michael A. Gleeson, Phys. Rev. Lett. 113, 053201.
DOI: PhysRevLett.113.053201
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
41
PR–14
PLASMOLYSIS AS A NOVEL APPROACH TO CO2-TO-FUEL CONVERSION
G.J. van Rooij,a D.C.M. van den Bekerom,a N. den Harder,a T. Minea,a G. Berden,b W.A.
Bongers,a R. Engeln,c M.F. Graswinckel,a E. Zoethout,a and M.C.M. van de Sandena,c
a
Dutch Institute for Fundamental Energy Research, P.O. box 6336, 5600 HH Eindhoven, The
Netherlands; Tel: +31 (0) 40 333 49 99 ; E-mail: g.j.vanrooij@differ.nl
b
Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld
7c, 6525 ED Nijmegen, The Netherlands.
c
Department of Applied Physics, Plasma and Materials Processing Group, Eindhoven
University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
Sustainable energy generation by means of wind or from solar radiation through photovoltaics
or concentrated solar power will be a significant part of the energy mix in 2025. Intermittency
(due to e.g. day/night cycle) as well as regional variation of these energy sources requires
means to store and transport energy on a large scale. A promising option is creating artificial
solar fuels (or CO2 neutral fuels) with sustainable energy, which can easily be deployed within
the present infrastructure for conventional fossil fuels.
A candidate raw material would be CO2 itself (fitting in carbon capture and utilization, CCU,
strategies). Presently, no efficient schemes are yet available for the conversion of CO2 into
fuels. A plasma chemical approach potentially offers high energy efficiency (up to 90%) due to
selectivity in the reaction processes that can be tailored via its inherently strong out-ofequilibrium processing conditions. At the same time, it is characterized by efficient and fast
power switching, low investment costs, no scarce materials required, and high power density,
which are all advantageous for addressing intermittency. In this presentation, the plasma
chemical approach will be introduced and examples will be discussed of research carried out at
the DIFFER to ultimately enable a scale up to industrial applications.
In particular, a common microwave reactor approach is evaluated experimentally with
Rayleigh scattering and Fourier transform infrared spectroscopy to assess gas temperatures
(exceeding 104 K) and conversion degrees (up to 30%), respectively. The results are
interpreted on the basis of estimates of the plasma dynamics obtained with electron energy
distribution functions calculated with a Boltzmann solver. It indicates that the intrinsic electron
energies are higher than is favorable for preferential vibrational excitation due to dissociative
excitation, which causes thermodynamic equilibrium chemistry still to dominate the initial
experiments. Novel reactor approaches are proposed to tailor the plasma dynamics to achieve
the non-equilibrium in which vibrational excitation is dominant.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
42
PR–15
ATMOSPHERIC PRESSURE PLASMA JETS IN HELIUM – THE ELECTRIC FIELD
AND THE CHARGE DELIVERED TO A DIELECTRIC SURFACE
A. Sobota1, E.T. Slikboer1, O. Guaitella2
1
EPG, Eindhoven University of Technology, Postbus 513, 5600MB Eindhoven, The
Netherlands
2
LPP, Ecole Polytechnique,Route de Saclay, 91128 Palaiseau CEDEX, France
The family of non-thermal atmospheric pressure discharges has been the focus of intense
research of a large number of research groups in the last fifteen years, as they are easy and
cheap to assemble and run, and exhibit properties that can be used in surface treatment or
biological applications. In this discharge family, the non-thermal atmospheric pressure plasma
jet commands a good deal of attention.
The mentioned applications all involve the presence of a surface (target for treatment) in the
vicinity of the discharge, and it has been shown that in many cases the presence of the surface
alters the properties of the discharge. There are many types of surfaces to consider, from
metals, dielectrics, to liquid surfaces, and they all leave a different mark on the discharge
properties. Still, most of the research has been done on plasma jets expanding freely into the
open air.
This paper reports on the electric field and charge measurements delivered to a dielectric
surface by an atmospheric-pressure plasma jet working in the bullet mode in helium. Imaging
will be presented alongside the measurements of charge, as it will be evident that the charge
distribution on the dielectric surface will mirror the observations obtained by imaging. The
central results contain the charge packed in one ionization wave leaving the capillary towards
the target, around 20 pC. The associated electric fields vary between 3×105 and 6×105 V/m.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
43
PR–16
ASML: PUSHING THE BOUNDARIES OF WHAT IS PHYSICALLY
POSSIBLE IN PRECISION ENGINEERING
V.A. Ignatova
| On-product Overlay Performance – Modeling| ASML Netherlands B.V.
Building 21 C2.039 | De Run 6501, 5504 DR Veldhoven | The Netherlands
T +31 61 13 452 572| F +31 40 268 5577 |
E velislava.ignatova @asml.com | I http://www.asml.com
ASML is a successful high-tech company headquartered in the Netherlands, which manufactures complex lithography machines. ASML is a technology leader and supplier to all leading
chip manufacturers around the world. The steady progress of the world’s technological evolution through faster, smarter, more energy-efficient yet more affordable chips is to a large extent
the result of technological breakthroughs at ASML.
One of the breakthroughs is the recently launched holistic lithography approach, which links
the lithography machines (scanners) to the metrology and computational lithography design
context. Customer device shrink roadmap is leading litho approaches for 7 nm technology to
drive for high density design to support advanced – mobile – applications. Based on metrology
and control SW we are moving from process window detection, through computational lithography design context, towards process window enhancement and process window control.
Litho-Insight (LIS) is an ASML application product for process control on all domains – overlay, focus and dose. There are number of steps to derive process corrections from wafer data:
measurement with ASML’s metrology tool YieldStar, determination of corrections in the Litho
InSight application and applying these corrections on the scanner. This calls for a holistic approach on OV process control where we split and quantify the systematic and noise contributions to all variations in the data at each of the steps.
ASML spends more than 1 billion Euros per year on R&D, our people have the freedom and
the resources to push boundaries of known technology. They work in close-knit, multidisciplinary teams and each day they listen to, learn from and exchange ideas with each other. It’s the
ideal environment for professional development and personal growth.
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
OP–6
DETECTION OF POWDER FORMATION IN
SiH4/H2 GLOW DISCHARGES
G. Alexiou, G. Tsigaras, A. Kalampounias,
E. Amanatides, D. Mataras
ORAL PRESENTATION OF
CONTRIBUTED PAPERS
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
47
OP–1
THEORETICAL INVESTIGATION OF COAXIAL DISCHARGE BASED ON 1D
FLUID MODEL
T. Bogdanov, E. Benova
St. Kliment Ohridski University of Sofia, Sofia, Bulgaria
Microwave discharges sustained by travelling electromagnetic waves have been intensively investigated in the past decades both theoretically and experimentally. The cylindrical
surface-wave-sustained discharge (SWD) has been studied in detail. The coaxial structure is a
relatively new type of a plasma source, which was proposed recently [1,2]. In the coaxial structure the plasma is produced outside the dielectric tube in a low-pressure chamber and a metal
rod is arranged at the dielectric tube axis.
The possible configurations depend on the radial distribution of different materials,
such as metal, vacuum, dielectric and plasma. We studied two configurations: metal–
dielectric–plasma and metal–dielectric–dielectric–plasma.
The purpose of this work is to present theoretical investigations of a coaxial surfacewave-sustained discharge (CSWD) at given configurations. The basic relations in our 1D fluid
model are the local dispersion relation and the wave energy balance equation obtained from
Maxwell’s equations [3]. The plasma is axially inhomogeneous and the dispersion relation
yields the so called phase diagrams – dependences between the normalized plasma density and
the dimensionless wave number. Axial profiles of the plasma density, wave power, electric and
magnetic field components are presented, too. From the behavior of the phase diagrams and the
axial profiles at different discharge configurations, we can obtain information about the ability
of the wave to sustain the plasma and about the wave and plasma characteristics.
References
[1]
E. Räuchle, J. Phys. IV France 8, 99 (1998)
[2]
S. Gritsinin, I. Kossyi, N. Malykh, M. Misakyan, S. Temchin, and Y. Bark, Preprint No
1, Russian Academy of Science, General Physics Institute, Moscow, 1999
[3]
E. Benova, Z. Neichev, Czechoslovak J. Phys. 52, D659-D665 (2002)
Acknowledgments
This work was supported by Project BG051 PO 001-3.3.06-0057, Operational Program Human
Resources Development 2007—2013 and partially supported by the Fund for Scientific Research at Sofia University under Grant No 187/2015.
48
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
OP–2
REACTION KINETICS, HEAVY PARTICLES AND RATE COEFFICIENTS IN HF
AND MW DISCHARGES IN ARGON AT ATMOSPHERIC PRESSURE
P. Marinova, M. Atanasova, E. Benova
Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 James Bourchier blvd., Sofia
1164, Bulgaria
The enormous variety of applications of plasmas originates from their capability to produce
large fluxes of photons and radicals. Plasma provides handy sources for surface treatment, surface modification etc. The latest applications require that the plasma sources be small, inexpensive and with sufficiently high concentrations of charged particles and chemically active species. Moreover, applications like medical plasmas need to be sustained in open air, and to have
considerably low gas temperature. An adequate solution to the above requirements is offered
by the atmospheric pressure surface-wave-sustained discharges (SWDs). These discharges are
usually plasma into non-equilibrium conditions and the prediction of the chemical composition
and the plasma properties becomes difficult as they can no longer be described by the classical
distribution laws of statistical physics.
The detailed knowledge of the discharge characteristics and their dependence on the externally
controlled parameters required by the practical applications can be provided in economical and
reliable way by a self-consistent model. For SWDs, the model consists of two parts – electrodynamics of the wave sustaining the discharge coupled with the plasma kinetics. Basis of the
kinetic model are Boltzmann’s equation and the particles balance and energy balance equations. We applied the model to argon plasma at atmospheric pressure.
Under high pressure conditions, a more detailed energy level diagram of argon should be considered and a large numbers of elementary processes should be taken into account. The following species are included in our model Ar, Ar(4s), Ar(4p), Ar(3d), Ar(5s), Ar(5p), Ar(4d),
Ar(6s), Ar2*, Ar+, Ar2+m, and Ar3+. All the excited states are considered as blocks of levels with
effective energy u k = ∑ u k , j / m where uk,j is the energy of each level in the block k and m is
j =1
their number. Additionally, averaged population is used.
By means of the model, the rate coefficients for direct and stepwise ionization and excitation,
the electron-neutral collision frequency, the excited atoms population and the ions densities are
obtained and presented in this study. The numerical calculations are carried for the following
discharge conditions: plasma radii – 0.05 cm, 0.1 cm and 0.2 cm, surface wave frequencies –
2 GHz, 1.5 GHz, 1 GHz and 0.5 GHz. The electron energy distribution functions at different
plasma densities are also obtained. The calculations confirm that the function is close to Maxwellian for high (~ 1015 cm–3) electron densities, but deviates from Maxwell’s distribution for
lower ionization ratios ne / N.
Acknowledgements: This work was supported by Project BG051 PO 001-3.3.06-0057 Operational Program Human Resources Development 2007-2013 and partially supported by the Fund
for Scientific Research at Sofia University under Grant No 187/2015.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
49
OP–3
MEASUREMENTS OF NONLINEAR SUSCEPTIBILITY OF MULTICOMPONENT
GLASSY MATRICES BY USING FEMTO SECOND Z-SCAN METHOD
G. Yankov and E. Iordanova
Institute of Solid State Physics, Bulgarian Academy of Science
72, Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
e-mail: mennefer2@abv.bg
The synthesis of any new solid-state material for laser applications and optical
telecommunications necessitates extensive research and provokes a broad scientific response.
Multi glassy matrices possessing variable nonlinear optical properties are one such an example.
Such mediums are interesting in the cases of optical switches and optical memories. The
earliest works dealing with tellurite glasses, numerous syntheses and studies of have been
conducted of new multicomponent glassy matrices possessing various nonlinear properties.
In the present work we report on the us of the z-scan method for non-linear coefficient
measurement of the synthesized glasses. This methodology is based on the transformation of
phase distortion into an amplitude distortion by using the Kerr effect.
The introduced z-scan method has the following advantages:
•
the diffraction problems are avoided by applying a CCD camera instead the typically
used power meter and diaphragm;
•
simultaneous measurement of the nonlinear constants is possible;
•
by using femtosecond laser, the influence of any thermal effects is minimized.
The data obtained allow us to derive the nonlinear absorption (NLA) and nonlinear refraction
(NLR). The nonlinear optical coefficients of fused silica was measured and compared with the
known data cited in the literature. The values of n2 and  of the glasses were determined.
OP–4
OPTICAL EMISSION SPECTROSCOPY OF PLASMA PRODUCED BY
LASER ABLATION OF FERROUS SULFIDE
S. Karatodorov, V, Mihailov and M. Grozeva
Institute of Solid State Physics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
In this work, optical emission spectroscopy studies on laser ablation plasma from a FeS target
in vacuum are reported. The aim of the work is to correlate the plasma emission with the
resulting deposition on unheated metallic substrates at different laser pulse energies and
different distances to the target. In order to achieve this goal, a thorough knowledge of the
plasma emission behavior is needed. Here the plasma behavior is characterized in space and
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
50
time by measuring the main plasma parameters – electron density and electron temperature.
The plasma emission is recorded in the interval 0 ÷ 1000 ns after the laser pulse at three
different positions above the target – 1 mm, 2.5 mm and 5 mm. From the spectra obtained, the
electron temperature is calculated by the Boltzmann plot method using a set of 15 Fe I lines
with known emission line parameters. A different set of Fe I lines is used to calculate the
electron density by the Stark broadening of the emission lines.
OP–5
FABRICATION OF METAL OXIDE NANOPARTICLES USING GAS
AGGREGATION SOURCE COMBINED WITH AUXILIARY OXYGEN RF PLASMA
А. Kuzminova, J. Hanus, A. Shelemin, O. Kylian and H. Biederman
Charles University Prague, Faculty of Mathematics and Physics, Prague, Czech Republic
Vacuum-based techniques for production of metal and metal oxide nanoparticles (NPs) have
been constantly developed and studied for many years. The magnetron sputtering or physical
vapor deposition methods are widely used to prepare metal NPs. These methods can be combined with gas aggregation sources (GAS) of different constructions that have been extensively
investigated for the last few decades. Applying oxygen, as a reactive gas, in a working gas admixture may allow one to produce metal oxide NPs. However, this approach can also lead to
undesirable effects, such as oxidation or poisoning of the magnetron target, which in turn may
cause instability of the process or a decrease of the deposition rate. Therefore, we proposed to
separate the oxidation process from the formation of metal NPs. In this case, we used gas aggregation source for fabrication of Ti or Ag nanoparticles. The nanoparticles formed then
passed through auxiliary oxygen RF plasma, where they were oxidized, and were finally deposited on the substrate positioned in the main deposition chamber (Fig. 1). A planar magnetron
with a metal target (Ag, Ti) was mounted inside the aggregation chamber, where argon at elevated pressure was used as a
working gas. The auxiliary plasma was maintained by an
external circular electrode attached onto a glass tube that was
mounted on the end of the aggregation chamber. RF power
was applied to electrodes at 5 and 10 W using argon/oxygen
as a working gas mixture. The pressure inside of the main
deposition chamber was 1 Pa.
Measurements of the chemical composition, morphology and
optical properties of the NPs produced have shown that the
additional oxygen RF plasma caused substantial oxidation of
both Ti and Ag. The possible use of oxidized Ag-AgO/Ag2O
NPs in antibacterial applications will be discussed.
Figure 1. Schematic representaAcknowledgement: This research has been suption of the set-up used for fabricaported by the Czech Science Foundation through
tion of metal oxide nanoparticles
Project 13-09853S.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
51
OP–6
GRADUAL ANNEALING EFFECT AND THERMAL STABILITY OF BULKHETEROJUNCTION SOLAR CELLS USING DPP(TBFU)2 DERIVATIVES AS
DONOR MATERIALS
Alexander Kovalenkoa, Jana Honováa, Martin Valaa, Stanislav Luňáka, Ladislav Feketeb,
Irena Kratochvílováb, Petra Horákovác, Lenka Dokládalovác, Lubomír Kubáčc and Martin
Weitera
a
Brno University of Technology, Faculty of Chemistry, Materials Research Centre,
Purkyňova 118, 612 00 Brno, Czech Republic.
b
Institute of Physics, Academy of Sciences Czech Republic v.v.i, Na Slovance 2,
CZ-182 21, Prague 8, Czech Republic.
c
Centre for Organic Chemistry Ltd., Rybitví 296, CZ-533 54 Rybitví, Czech Republic.
Currently, polymer and small molecules (SMs) bulk-heterojunction (BHJ) organic solar cells
(SCs) exceeding 11 % power conversion efficiency (PCE) and lifetimes above 1000 h under
continuous illumination are attracting particular interest due to their flexibility, color tunability
and, predominantly, potentially low production cost. Considering SMs as a donor material, despite of the recent successful results, they still lag behind the polymer BHJ solar cells. However small-molecules BHJ SCs do not depend on a polymer weight distribution, thus do not suffer from batch-to-batch differences. One of the most promising structural class of the donors in
BHJ SCs - diketopyrrolopyrrole (DPP) derivatives - show excellent photovoltaic performance
both as a part of polymers or dimers, because of a low band gap, enabling them to absorb a
large portion of the solar spectrum, as well as an ability to be further-functionalized to match
the parameters required for the photovoltaic applications. Among the DPP monomers,
DPP(TBFu)2 ethyl-hexyl alkylated derivative showing high power-conversion efficiency (PCE)
up to 4.4 - 4.8% with PC70BM and 4.0% with PC60BM, represents the most successful design. Applying a solvent annealing for the DPP(TBFu)2: PC70BM blend 5% of PCE can be exceeded, which is, up to now, the highest reported PCE among the monomeric DPP derivatives.
Consequently, relatively easily (as compared to e.g. bis-DPPs) obtainable DPP(TBFu)2 is often
used as a benchmark compound in the current research dealing with new SM donors, acceptors
or tandem cells. The attempts to modify DPP(TBFu)2 structure using different heteroatoms
brought only lower PCE. DPP(TBFu)2 belongs to SM donors, for which the relationships between the structure and various aspects of the photovoltaic activity such as hole mobility were
understood to the most detailed extent.
PCE of BHJ SCs using DPP(TBFu)2 as a donor is known to be extremely sensitive to temperature annealing. Furthermore, to the best of our knowledge, PEDOT:PSS is the only holeselective contact (HSC) reported in the previous studies. Here we report a new method of the
gradual annealing, causing the progressive reorganization of the donor-acceptor bulkheterojunction, improving the solar cells performance. It is known that the MoO3 used as HSC
instead of PEDOT:PSS can improve in some cases PCE of BHJ SCs, so we studied its effect in
detail, including the thermal stability of the contacts. Moreover, we have tested the new
DPP(TBFu)2 derivatives with ethyl-hexyl solubilization groups substituted by ethyl-hexyl acetate and diethyl acetal groups. It was expected that the electron-accepting effect of these substituents could stabilize HOMO level of a donor and thus improve the open-circuit voltage of the
cell.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
52
OP–7
DETECTION OF POWDER FORMATION IN SiH4/H2 GLOW DISCHARGES
G. Alexiou, G. Tsigaras, A. Kalampounias, E. Amanatides, D. Mataras
Plasma Technology Laboratory, Department of Chemical Engineering, University of Patras
Hydrogenated microcrystalline (μc-Si:H) and amorphous (a-Si:H) silicon thin films have
attracted particular attention due to their application to optoelectronic devices. The method that
is commonly used for the production of these films, is plasma enhanced chemical vapor
deposition (PECVD) using radio frequency (RF), through capacitively coupled silane/hydrogen
discharges. In the deposition of these films, it is important to increase the deposition rate while
maintaining the high quality of the film. Many parameters of the discharge affect the deposition
rate and the deposited film quality. RF power, as well as the working pressure have been
increased to achieve higher deposition rates. However, these two parameters have the common
drawback of increasing the powder formation in the discharge which affects the film’s quality.
For this reason, fast powder detection in SiH4/H2 discharges is of special interest.
Different techniques have been proposed to detect the powder formation in silane/hydrogen
discharges. In this work, we used different techniques in order to monitor the nucleation and
formation of dust in SiH4/H2 discharges.
The thin films were deposited in a capacitively coupled, ultra-high vacuum (10-8 Torr base
vacuum) parallel plate reactor under different conditions of pressure and RF power. Corning
7059 glasses were used as substrates at a constant temperature of 200 oC. The SiH4
concentration in H2, the total flow rate and the interelectrode distance were kept constant.
Raman crystallinity and in-situ laser reflectance interferometry (LRI) were used in order to
estimate the crystalline volume fraction and the deposition rate, respectively.
The formation of particles was found to produce instabilities in both the electrical and optical
properties of the discharge. These instabilities were monitored through different time–resolved
plasma diagnostics, as forward and reflected power measurements, discharge current
harmonics, self-bias voltage (Vdc), optical emission spectroscopy (OES) and laser light
scattering (LLS). These techniques were compared in terms of their sensitivity and their
applicability for early point detection of the particles nucleation phase. The advantages and
disadvantages of the techniques are discussed, together with the effect of particles formation on
the film quality and deposition rate.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
53
OP–8
RESISTIVITY IN Al DOPED ZnO NANOLAYERS OBTAINED BY ATOMIC LAYER
DEPOZITION
Blagoy S. Blagoev, Dimiter Z. Dimitrov, Vladimir B. Mehandzhiev, Jerome B. Leclercq,
Peter K. Sveshtarov
Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee
blvd, 1784 Sofia, Bulgaria
Transparent conducting oxides (TCO) have been extensively investigated in recent years due
to their applications in electronics, optoelectronics and photovoltaics. Zinc oxide (ZnO) is one
of the most competitive semiconductors because of its high transmittance in the visible range
and low dc resistivity. Small additions of Al as a dopant element to ZnO films strongly
decrease the resistance without worsening the optical properties. Atomic layer deposition
(ALD) is one of the most suitable techniques for obtaining uniform ultra thin films on large
areas. The dopant incorporation with atomic precision could be easily performed by ALD.
In this work we present ZnO nanolayers with different concentration of Al dopant grown by
atomic layer deposition. For deposition of ZnO films and Al addition we used liquid precursors
DEZ and TMA respectively alternating with H2O. In spite of the great number of publications
for ZnO:Al, there is no enough information on studying the resistivity of samples prepared by
ALD. We investigated in more detail the influence of the Al dopant on samples’ resistivity.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
54
OP–9
COMPARATIVE STUDY OF RF REACTIVE MAGNETRON SPUTTERING AND
SOL-GEL DEPOSITION OF UV INDUCED SUPERHYDROPHILIC TiOx THIN
FILMS
V.E. Vrakatseli, E. Amanatides and D. Mataras
University of Patras, Department of Chemical Engineering
Plasma Technology Laboratory
Titania (TiO2) thin films possess unique properties, such as photocatalytic activity and photoinduced hydrophilicity, which is the ability of TiO2 surfaces to alternate their wetting characteristics from hydrophobic or relatively hydrophilic to super hydrophilic under UV irradiation.
Superhydrophilic / amphiphilic TiO2 thin films are of particular interest because of the great
prospects for many new applications, such as self-cleaning, anti-fogging and anti-ice surfaces.
Nevertheless, their application on non-thermal resistive polymeric substrates demands a low
temperature deposition method. The different deposition methods applied could severely influence the resulting thin film’s structure, properties and functionality, but they also have limitations, advantages and disadvantages of various aspects. Therefore, the choice of a proper method for the deposition of the desired TiO2 film is of significant importance related to its properties, applicability and resulting quality.
In this work, ΤiOx and TiOx-like thin films were deposited on PEEK (Polyether ether ketone)
substrates by the two most common low-temperature deposition methods and the resulting
films were compared in terms of their properties and photoinduced hydrophilicity.
TiOx thin films were deposited in a homemade ultra-high vacuum radio frequency
(13.56 MHz) magnetron sputtering reactor using a Ti target, Ar as the buffer gas and O2 as the
reactive gas. The effect of RF plasma sputtering parameters, such as the plasma power and the
Ar/O2 composition, on the deposited films was evaluated. On the other hand, titanium tetrasiopropoxide (TTiP) alcoholic solutions (TTiP/iPrOH/H2O and TTiP/MetOH/Η2Ο) were spin
coated on the PEEK substrates. The sol-gel spin-coating deposited thin films were examined
after they were physically dried at room temperature, but also after they were treated by low
temperature Ar/O2 atmospheric pressure plasma using a plasma jet source.
Both methods resulted in adhesive, transparent and UV induced superhydrophilic TiOx and
TiOx-like thin films. The RF reactive magnetron sputtered thin films and the TTIP sol gel deposited films were compared in terms of their UV induced hydrophilicity, hydrophilicity persistence in dark, as well as their optical and structural properties.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
55
OP–10
STAND FOR COATING DEPOSITION AND COATING/MATERIAL TESTING.
A.A. Ayrapetov, L.B. Begrambekov , A.E. Evsin, A.V. Grunin, A.A. Gordeev, A.M. Zakharov,
A.M. Kalachev, Ya.A. Sadovskiy, P.A. Shigin
National Research Nuclear University «MEPhI», Moscow, Russia
The paper describes a new laboratory stand constructed for film deposition and for testing of
deposited films and materials under pulsed and constant heat, ion and electron irradiation.
The film is formed on substrates by atoms sputtered from targets of different materials by ions
of argon plasma ignited between heated tungsten cathode and anode. The energy and current of
the ions sputtering targets can be varied separately. This makes possible deposition of coating
with various components, multi-layer coating etc.
To investigate the ability of the deposited films to trap hydrogen isotopes they are added to
plasma during the film deposition. A mass-spectrometer is used to measure the composition of
the residual and working gasses. The low residual pressure allows for less than 0,1 % of
impurities in deposited coatings. The substrates of dimensions 15×15 mm2 are water cooled
during deposition and their temperature can be fixed during deposition between 300 K and
900 K. Before and during deposition, the substrate with the deposited film cab be irradiated by
plasma ions for achieving better adhesion and better structural property of the film,
respectively.
For testing of any material samples or deposited films by plasma electron or ion irradiation
they are biased, correspondingly, positively or negatively. Hydrogen is used as a working gas
for plasma discharge thus reducing sample sputtering by ion irradiation. The parameters of the
sample irradiation can be varied over wide limits by changing the plasma density, bias potential
and relative position of sample and plasma chamber. The energies of the ions or electrons can
be up to 25 keV. Up to 4000 W (40 MW/m2 power density in the case of a 1 cm2 sample) of
power could be applied during both continuous and pulsed regimes. Pulses of 1-99 % duty
cycle at 0-500 Hz can be applied to the sample. Heating of the samples up to 2500 °C is
available. A pulsed particle load can be combined with a steady-state load. Thermal cycling of
the sample is realized by irradiation of the substrate’s backside by electron or ion beams. The
heating flux can irradiate the whole sample or be focused at its center (spot of ~4 mm2).
Sample dimensions up to 100 mm in diameter are possible. The backside of the tested samples
can be actively cooled.
Acknowledgements: This work was supported by the Competitiveness Growth Program of the
Federal Autonomous Educational Institution of Higher Professional Education National
Research Nuclear University MEPhI and by the Ministry of Education and Science of the
Russian Federation (agreement contract №14.575.21.0049 of 27.06.14).
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
56
OP–11
INVESTIGATION OF ARC SPOT MOTION ALONG THE ELECTRODES IN A
PLASMA TORCH
V. Sauchyn1, I. Khvedchyn1
1
Luikov Heat and Mass Transfer Institute of the National Academy of Sciences of Belarus
The process was investigated of the arc spot motion along the surface of cylindrical electrodes
in a plasma torch with gas vortex stabilization of the arc. Experiments were conducted with a
model of the plasma torch with onesided outflow. The design of the plasma torch allows us to
place a metal foil with a thickness of 0.1 mm inside the electrodes. Arc spots are moved due to
the gas vortex flow. They leave tracks on the foil as a results of overheating.
The geometrical parameters of the tracks were measured, such as arc spots size, distance between two consecutive spots, tracks length and direction. All this data were correlated with oscillograms of the arc current and voltage.
The parameters of the arc spots movement along the electrodes depend to a large extent on the
plasma forming gas consumption and arc current strength. It should be mentioned that the
anode and cathode arc spots are different. Two mechanisms of arc spot movement can be defined in the case of a cathode spot. The first one is when there is continuous gliding and track is
inseparable. The second one is discontinuous arc jumping caused by shunting of arc with electrode surface. The first mechanism is about 30 % arc movement and decreases with plasma
forming gas consumption and decreasing of current strength. Life time of arc spot in one place
varies widely from 10-5 to 10-3 seconds. So the size of tracks vary too from 10-7 to 10-5 mm2.
With plasma forming gas consumption increasing cathode arc spots make smooth lines. The
distance of spot jump increases insignificant. With increasing of current strength up to 200 A
arc spot splitting to 2 or more spots takes place. Life time of new spots is up to some microseconds. It should be point out that increasing of plasma forming gas consumption decreases
probability of arc spot splitting and needs to increase current strength to start the process.
Anode arc spots as opposed to cathode ones move only by jumping. Distance between two
spots is about 1-5 mm and doesn’t depend on plasma forming gas consumption and current
strength. Shape of spot is close to circle with smooth border. Its diameter is from 0.2 to 3 mm.
Life time of arc spot in one place varies from 10-5 to 2·10-4 seconds.
Anode arc spot can split as the cathode one. It should be mentioned that the splitting process
needs less current strength and dependence on plasma forming gas consumption is weak.
Longitudinal and circular velocity of arc spot movements was observed quantity depending on
plasma forming gas consumption and current strength. Velocity of cathode arc spot movement
exceeds anode one.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
57
OP–12
TRANSITION METAL OXIDES NANOPARTICLES, NANOFIBERS AND CORESHELL NANOCOMPOSITES PREPARED BY ANNEALING, ELECTROSPINNING
AND ALD FOR GAS SENSING, PHOTOCATALYTIC AND ELECTROCHROMIC
APPLICATIONS
S.I. Boyadjiev1, V.B. Georgieva2, I.M. Szilágyi1,3
1
MTA-BME Technical Analytical Chemistry Research Group, Szent Gellért tér 4, Budapest,
H-1111, Hungary, e-mail: boiajiev@gmail.com
2
“Georgi Nadjakov” Institute of Solid State Physics, Bulgarian Academy of Sciences, 72
Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria, e-mail: lazarova@issp.bas.bg
3
Budapest University of Technology and Economics, Department of Inorganic and Analytical
Chemistry, Szent Gellért tér 4, Budapest, H-1111, Hungary, e-mail: imre.szilagyi@mail.bme.hu
Many transition metal oxides are widely used for gas sensing, photocatalytic and
electrochromic applications. Their properties might be improved by making composites of
them with other semiconductor oxides. In the present study, two approaches to prepare coreshell nanocomposites of several transition metal oxides were used. By combining annealing
and atomic layer deposition (ALD), pure WO3 and core/shell WO3/TiO2 nanoparticles were
prepared and tested as gas sensors, photocatalysts and electrochromic materials. The
performance of these nanocomposites can be increased by preparing them as nanofibers with a
high specific surface. In this direction, pure ZnO and TiO2, as well as core/shell ZnO/TiO2 and
TiO2/ZnO nanofibers were prepared by electrospinning, annealing and ALD, and also tested for
gas sensing and photocatalysis.
The composition, structure and morphology of the pure and composite nanoparticles and
nanofibers were characterized by TG/DTA-MS, TEM, SEM-EDX, XRD, UV-Vis, FTIR and
Raman spectroscopies. We investigated how the semiconductor oxides interacted with each
other when a pure oxide particle or fiber was covered with an ultra-thin film of other oxide and
how exchanging the core and shell materials influenced their properties.
Fig. 1. TEM image of a core/shell composite WO3/TiO2 nanoparticle
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
PA–2
A STUDY OF SPUTTERED TUNGSTEN ATOMS
BY LASER INDUCED FLUORESCENCE
A. Georgiev, A. Pashov, D. Michailova,
St. Zapryanov and A. Blagoev
POSTER SESSION A:
PLASMA-SURFACE INTERACTION AND
PLASMA DIAGNOSTICS. MODELING AND
COMPUTER SIMULATION
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
61
PA–1
INVESTIGATION OF THE HYDROGEN NEUTRALS IN DISCHARGE SOURCE
USED FOR PRODUCTION OF METAL HYDRIDES
I. Bozhinova, S. Iordanova, A. Pashov
Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 J. Bourchier blvd. 1164
Sofia, Bulgaria
The main properties are examined of a discharge tube designed for production of metal hydrides (in particular NiH), which are of interest in astronomy. The results from laser absorption
measurements reveal the optimum gas composition and pressure and discharge current at
which the highest concentration of NiH species is achieved in the tube volume [1]. Under the
optimal working conditions, however, the emission from the center of the tube is significant,
contrary to our expectations. The dark center of the tube is suitable for laser-induced fluorescence measurements. Moreover, when heating the cathodes, the NiH absorption signals drop.
These observations guided us to examine experimentally some of the elementary processes in
the gas discharge and how the NiH molecules are formed in this source.
This contribution is devoted to an investigation of the hydrogen neutrals by using optical emission spectroscopy. We used the interferometric setup from Ref. [2] to estimate the temperature
of various groups of hydrogen atoms. The measurements show that the change of the main discharge parameters (gas pressure and current) changes the relative intensity of the atomic and
molecular lines and the temperature of the atoms. The complicated line shape of the hydrogen
H spectral line is examined in detail. The connection between the parameters of the neutral
hydrogen particles and the production of NiH is discussed.
References:
[1] I. Bozhinova, St. Kolev, M. Dimitrova, Tsv. Popov, and A. Pashov, Discharge tube with
coaxial geometry for efficient production of metal hydrides, Rev. Sci. Instrum. 84, Issue 9,
093107 (2013); http://dx.doi.org/10.1063/1.4820959 (9 pages), ISSN: 0034-6748, IF=1.602
[2] S. Iordanova and A. Pashov. ”Spectral diagnostics based on Doppler-broadened Hline
shape in a single element of a matrix source”. AIP Conf. Proc., 1655:040012, 2015.
PA–2
A STUDY OF SPUTTERED TUNGSTEN ATOMS BY LASER INDUCED
FLUORESCENCE
A.Georgiev, A. Pashov, D. Michailova*, St. Zapryanov and A. Blagoev
University of Sofia, 5 J Bourchier blvd., 1164 Sofia, Bulgaria
* Technical University of Eindhoven, The Netherlands
We report on a spectroscopic method for determination of the density of sputtered tungsten
atoms. The method is based on registration of the fluorescence at 3024,9 Ǻ following laser excitation of the WI 2879,4 Ǻ resonance line. The tungsten atoms are sputtered in a hollow cathode tube of a special rectangular geometry in order to increase the atomic density in the cen-
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
62
tral region. The hollow cathode is placed in a White multi pass cell, which influences also the
geometry of the cathode. The discharge is operated in a pulsed regime with a repetition rate of
20 Hz and a pulse duration of 3 ms. The laser pulses (generated by a system of a pulsed
Nd:YAG pump laser and a dye laser with a frequency doubler) are synchronized with the discharge, but a delay between the discharge and the Q-switch of the Nd:YAG laser can be introduced. This delay, the duration of the current pulse and the laser intensity can be varied; one
can thus study the fluorescence of the W atoms in an afterglow mode. The laser-induced fluorescence is collected in a direction perpendicular to the laser beam, filtered by a 35 cm monochromator and registered by a photomultiplier. We will present the decay of the W density
for delays up to 2.5 ms. The method for estimation of the atomic density from the registered
signals as well as the possibility to make quantitative measurements will be discussed.
PA–3
LASER ABLATION THRESHOLD DETERMINATION
BY SURFACE PHOTO-CHARGE EFFECT
V. Mihailov, S. Karatodorov and O. Ivanov
Institute of Solid State Physics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
Experimental results are presented concerning a new technique for measurement of the laser
ablation threshold by using the surface photo-charge effect. To demonstrate the utility of the
proposed technique, the effect of laser power on both the magnitude and time evolution of the
surface photo-charge voltage in Si are investigated.
It has been established that there are two regimes characterizing the laser-target interaction
which depend on the laser intensity. When the laser pulse energy is less than the laser ablation
threshold, there is no destruction of the surface. At the same time, a strong and quickly relaxing
photo-induced signal is observed. With increasing the laser pulse energy beyond this limit,
destruction of the surface starts and craters are being formed accompanied by a dramatic
change in the shape of the signal. A small increase in the amplitude is accompanied by a
significant broadening of the signal and the appearance of a second component with opposite
polarity. Hence, by varying the laser intensity applied, the pulsed laser-induced signal can be
used for in situ monitoring of the onset of surface damage.
PA–4
QUALITATIVE AND QUANTITATIVE LASER-INDUCED BREAKDOWN
SPECTROSCOPY OF BRONZE OBJECTS
V. Tankova, K. Blagoev, M. Grozeva, G. Malcheva
Institute of Solid State Physics, 72 Tzarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
Laser-induced breakdown spectroscopy (LIBS) is an analytical technique for qualitative and
quantitative elemental analysis of solids, liquids and gasses. In this work, the method was applied to investigating archeological bronze objects. The analytical information obtained by
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
63
LIBS was used for qualitative determination of the elements in the material used for manufacturing the objects under study. Quantitative chemical analysis was also performed after generating calibration curves with standards of similar matrix composition. Quantitative estimation
of the elemental concentration of the bulk of the samples and of the surface layer of the objects
was performed. Results of the quantitative analyses gave indications about the manufacturing
process of the objects.
PA–5
LIBS ANALYSIS OF VALUABLE PRECIOUS METAL MUSEUM OBJECTS
D. Yordanova1, G. Malcheva1, V. Tankova1, A. Pirovska2, M. Grozeva1
1
Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia, Bulgaria
2
Maritza-Iztok Archaeological Museum, Radnevo, Bulgaria
Laser induced breakdown spectroscopy (LIBS) is a versatile elemental analysis method with a
great potential in the field of artworks. The unique capabilities of this laser-based method
permit one to perform investigations of cultural heritage monuments, which has not so far been
possible by conventional laboratory techniques.
We report results of a qualitative elemental analysis of two precious metal artefacts of different
periods, found in the region of Stara Zagora: silver pectoral and gold pectoral. Elemental
composition analysis was conducted at characteristic spots on the surface and in depth. As the
investigated objects are of high value, the desire was to obtain reliable spectra for analysis
causing as less damage as possible. That is why during this study we limited the measurements
up to five shots at a spot, causing a crater hardly visible by a naked eye.
The elemental composition of the two artefacts differed: the ancient (B.C.) artefact (the silver
pectoral) hd been manufactured of high-quality silver with traces of copper and gold, while the
ancient (B.C.) artefact (the gold pectoral) had been manufactured of high-quality gold with
traces of copper and silver.
The measurements were performed by a LIBSCAN 25 portable system for near-field
measurements.
PA–6
IDENTIFICATION OF METAL SAMPLES BY COLLISIONAL ELECTRON
SPECTROSCOPY (CES)
M. Stefanovaa, P. Pramatarova, A. Saifutdinovb and A. Kudryavtsevb
a
Institute of Solid State Physics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
b
St.Petersburg State University, 7-9 Universitetskaya nab., St.Petersburg, 199034, Russia
The non-local plasma of a short (without positive column) dc Ar microdischarge at intermediate pressures is utilized for the detection and identification of atoms from Au samples. The
identification of the analyzed metal is carried out by using the electron energy spectra of
groups of fast nonlocal electrons − characteristic electrons released in the Penning ionization of
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
64
the Au atoms by Ar metastable atoms and molecules. The recently developed collisional electron spectroscopy (CES) method for gas analysis allows one to measure the energy spectra of
the Penning electrons and to determine their energy εp in the collisional mode at intermediate
and high pressures [1, 2]. In nonlocal plasma [3], the different groups of electrons lose negligible portion of their energy by collisions in the volume and behave independently of each other
over the specific discharge dimension. As a result, sharp peaks in the EEDF are formed. The
recorded EEDF in main gas Ar at pressures 10 – 50 Torr with small admixture of Au atoms are
characterised by the presence of well expressed peaks, at the energies of the Penning electrons
appearance, which are 2.3 eV and 1.2 eV. The acquisition of the electron energy spectra is performed using an additional electrode − a sensor located at the boundary of the discharge volume. Using the measured energy of the maxima εpAu, and ionization potential εiAu, identification of the Au atoms is accomplished. Cathode sputtering is used for atomization of the metal
under analysis. Absolute calibration of the energy scale is made by using the characteristic Ar
maxima due to pair collisions between Ar metastable atoms and molecules, and super-elastic
collisions. This study demonstrates the possibility of creating a novel microplasma analyzer for
atoms from metal samples.
[1] A. A. Kudryavtsev, A. B. Tsyganov and A. S. Chirtsov, Patent of Russian Federation 2,
422,812 (27 June 2011)
[2] A. Kudryavtsev, P. Pramatarov, M. Stefanova and N. Khromоv, J. of Instrumentation IOP,
JINST, 2012, 7 PO7002, 1– 13.
[3] L. D. Tsendin, Plasma Sources Sci. Technol. 1995, 4, 200-211.
PA–7
DETERMINATION OF SPATIALLY- AND TIME-RESOLVED ELECTRON
TEMPERATURE IN NANOSECOND PULSED LUNGITUDINAL DISCHARGES
S. I. Slaveeva1, T. P. Chernogorova2, K. A. Temelkov1
1
Metal Vapor Lasers Laboratory, Institute of Solid State Physics,
Bulgarian Academy of Sciences, 72, Tzarigradsko Chaussee, 1784 Sofia, Bulgaria
2
Faculty of Mathematics and Informatics, Sofia University,
3 James Bourchier blvd., 1164 Sofia, Bulgaria
stisl80@abv.bg
The electron temperature, together with the gas temperature and the electron density are the
most fundamental plasma parameters that play a very important role in understanding the numerous phenomena in gaseous discharges, laser physics, plasma technologies, gas-discharge
mass spectroscopy, absorption and emission spectroscopy, and plasma in general.
Elastic and inelastic electron-heavy particle collisions, such as electron impact excitation, deexcitation, and ionization, as well as three-body recombination, depend thoroughly on the electron temperature. Measurements of the electron temperature by Langmuir probes are not applicable to high-voltage and high-current nanosecond pulsed longitudinal discharges (NPLDs).
Laser Thomson scattering measurements of the electron temperature have been proved to be
effective but challenging because of the low signal and excessive stray light, as well as the
complicated experimental setup.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
65
Under conditions of a local thermodynamic equilibrium, measurement of the relative intensities
of some He and Ne spectral lines, originating from different upper levels, enabled us to determine the stationary electron temperature, as well as the time-resolved electron temperature in
the discharge afterglow, in a NPLD in He, Ne and Ne-He mixtures [1]. This type of discharge
is widely used for excitation of high-power metal and metal halide vapor lasers oscillating in
the deep ultraviolet (DUV), visible, near infrared (NIR) and middle infrared (MIR) spectral
ranges. Using the experimental results obtained for the stationary electron temperature [1], and
deriving using the Wiedemann-Franz law the electronic thermal conductivity as well, an analytical solution of the steady-state heat conduction equation was found for a uniform input.
A 2D (r, t) numerical model was developed for determination of the spatially- and timeresolved electron temperature in various NPLDs used for excitation of the abovementioned
high-power metal and metal halide vapor lasers. The preliminary results showed that the electronic thermal conductivity as derived using the Wiedemann-Franz law results in obtaining an
unreasonable solution of the nonstationary heat conduction equation for electrons. Scanning the
electronic thermal conductivity, radial and time dependences of the electron temperature,
which reflect the physical reality, were obtained.
References:
[1] K.A. Temelkov, S.I. Slaveeva, N.K. Vuchkov, “Analytical Calculation of Gas Temperature
and Experimental Determination of Electron Temperature in Gas Discharge in He-Ne Mixtures”, IEEE Transactions on Plasma Science, vol. 39, no. 3, pp. 831-835, 2011.
PA–8
THEORETICAL STUDY ON THERMAL CONDUCTIVITIES OF VARIOUS GAS
MIXTRES THROUGH GENERALIZED LENNARD-JONES INTERACTION
POTENTIAL FOR APPLICATION IN GAS-DISCHARGE LASERS
K. A. Temelkov, S. I. Slaveeva and Yu. I. Fedchenko
Metal Vapor Lasers Laboratory, Georgi Nadjakov Institute of Solid State Physics,
Bulgarian Academy of Sciences
72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria
temelkov@issp.bas.bg
One of the main problems of plasma physics is to determine characteristic constants for
basic processes in plasma, such as asymmetric charge transfer, Penning ionization, elastic and
inelastic electron-heavy particle collisions, heat conduction, diffusion and radiative transitions.
This will be very helpful in understanding and predicting numerous phenomena in gaseous discharges, laser physics, plasma technologies, spectroscopy, and plasmas in general. The abovementioned processes determine the creation of population inversion and output parameters in a
number of high-power metal and metal halide vapor lasers oscillating in the deep ultraviolet
(DUV), visible, near infrared (NIR) and middle infrared (MIR) spectral ranges.
The characteristic constants for the heavy particle processes depend on the gas
temperature. In particular, for metal or metal halide vapor lasers, the thermal mode, as well as
the radial temperature distribution, are of considerable importance for the stability of the laser
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
66
operation and also for the achievement of high output characteristics, because it controls not
only the laser level kinetics, but also the concentration of the active particles, i.e. particles on
whose transition laser oscillation is obtained. The experimental techniques for gas temperature
measurements using measurements of the Doppler spectral lines broadening and the focal
distance of a thermal lens are definitely imprecise.
The constants B and a, which determine the thermal conductivity allometrically expressed, could be obtained through fitting the existing experimental data. Unfortunately, except
for rare gasses, data for the thermal conductivities of chemical elements of our interest are
either very scarce in the literature or are within a narrow temperature range, which is not of
interest. That is why it is necessary to calculate the thermal conductivities in order to obtain the
gas temperature distribution via solving the heat conduction equation. The generalized (m-n)
Lennard-Jones interaction potential, namely ϕ(r) = A.r –n – B.r –m, is used to calculate the
thermal conductivities of helium, neon, copper, bromine, hydrogen and strontium.
The thermal conductivities of binary gas systems are calculated on the basis of the
empirical method of Brokaw, combination rules for Lennard-Jones interaction potential and
Wassiljewa’s formula for the case of gas discharges in helium and neon with small admixtures
of copper, bromine, hydrogen and strontium. The binary gas mixtures considered, i.e. the
pressures of the two gas components, are optimal for achieving maximal output characteristics
of the lasers excited in a nanosecond pulsed longitudinal discharge in these mixtures.
PA–9
INVESTIGATION OF PARAMETERS OF GAS DISCHARGE IN AN ARGONOXYGEN MIXTURE FOR OPTIMIZATION OF THE GROWTH OF OXIDE FILMS
M. Mitov1, V. Videkov1, Tsv. Popov2, K. Raykov1, A. Bankova1
1
Technical University of Sofia, 8 Kliment Ohridski blvd., 1000 Sofia, Bulgaria
2
Faculty of Physics, St. Kliment Ohridski University of Sofia,
5, J. Bourchier blvd., 1164 Sofia, Bulgaria
The oxide film properties and the methods of their production are of great interest. Oxide films
find many applications in micro and nano electronics. They can be a part of the chip structure,
an insulator in supercapacitors, mechanical elements in micro-electro-mechanical systems, a
dielectric base for micro modules and many others. The paper presents an investigation of gas
discharge parameters in an argon-oxygen mixture during growth of an oxide films under different discharge conditions. The results obtained allow optimization of the discharge in order to
obtain uniform oxide layers with an exact thickness. Using the film being grown as a Langmuir
probe allows us to monitor the film thickness in real time.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
67
PA–10
MONTE CARLO ESTIMATES OF EDGE PARTICLE SOURCES IN TJ-II PLASMAS
D. López-Bruna1, Tsv. Popov2, E.de la Cal1
1
Laboratorio Nacional de Fusión, CIEMAT, 28040 Madrid (Spain)
2
Faculty of Physics, University of Sofia, Sofia (Bulgaria)
The evaluation of the sources in magnetic confinement fusion devices is a difficult and
complex task. In most cases, source terms do not conform to flux surfaces and a threedimensional (3D) calculation is mandatory. This is especially true in the case of particle
sources, which involve the motion of neutrals through the vacuum vessel (VV) and the
contained plasma, together with the atomic physics and some description of the plasma-wall
interaction.
In medium sized or large tokamak plasmas, a one-dimensional calculation can be sufficient to
yield a first approximation of the neutrals distribution and the corresponding electron source
[1], although detailed results near the divertor require 3D calculations. Matters are commonly
more complicated in stellarators. The TJ-II Heliac is somewhat singular because the plasmawall interaction is strong in a complicated VV geometry. For example, in addition to the
possible insertion of poloidal limiters, typical plasmas are limited by the “hard core”, a metallic
case that protects the central conductors [2].
We present 3D calculations of the effects of gas puffing, limiter insertion and wall conditioning
(boronized or lithiumized wall coating) based on the EIRENE Monte Carlo code [3] adapted to
the TJ-II geometry [4]. The output consists of 3D distributions for neutrals and ionized species,
and estimates of diagnostic measurements in the appropriate geometry, so that the calculations
can be compared with experimental measurements. The importance of performing 3D
calculations is stressed when the experiments involve specific geometries, like gas puffing
valves, diagnostic chords or solid angles through which radiation is collected. Examples are
given for (i) the evolution of Hα light during a radiative collapse following the L-H transition,
(ii) CX spectra at a specific time of a discharge, (iii) helium 760 mm light recorded near a gaspuffing valve in He-plasmas and (iv) electron source from ionization of neutrals in relation
with electric probe measurements.
References
[1] S. Rehker, H. Wobig, Plasma Phys. 15 1083 (1973)
[2] C. Alejaldre et al., Fusion Technol. 17 131 (1990)
[3] D. Reiter, The EIRENE code user manual (including: B2-EIRENE interface) (2005),
http://www.eirene.de/html/manual.html
[4] J. Guasp, A. Salas, Manual for the use of Eirene at Ciemat,
http://www.eirene.de/html/recent reports.html
68
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
PA–11
PERIPHERAL PLASMA CHARACTERISTICS IN THE URAGAN-3M TORSATRON
A. Kasilov, L. Grigor’eva, V. Chechkin, A. Beletskii, R. Pavlichenko, A. Lozin, M. Kozulya,
N. Zamanov, Y. Mironov, V. Voitsenya
Institute of Plasma Physics, National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
andrewkasilov@gmail.com
In the  = 3/ m= 9 Uragan-3M (U-3M) torsatron (R0 = 100 cm, a ≈ 12 cm, ι( a )/2π ≈ 0.3,
Вφ ≲ 1 Т), hydrogen plasma is produced and heated by RF fields in the Alfvén range of frequencies (ω ≲ ωci). In the work reported, to introduce RF power into the plasma, an unshielded
frame-like antenna is used with a broad spectrum of generated parallel wavelengths [1]. The
plasma parameters distributions (electron density ne, electron temperature Te, floating potential
Vf) are studied by Langmuir probes in the space between the helical winding cases and the last
closed flux surface in a poloidal torus cross-section far from the antenna and in two crosssections in the region of antenna location, one of them crossing the area bounded by the antenna frame. The measurements are carried out in two discharge regimes [2], one of them (regime
1) is characterized by a low average density ne ~ (1–3)×1012 cm-3, a high electron temperature
(Terad up to 800 eV) and a large plasma loss from the confinement volume (by the diverted
plasma flow magnitude), while a higher density ne ≲ 7×1012 cm-3, a lower temperature (tens
eV) and a low plasma loss are inherent to the other regime (regime 2). Comparing the values of
the electron density in the divertor flows and peripheral plasma, it was deduced that plasma
divertor flows are predominantly formed by the plasma outgoing from the confinement volume. The up-down asymmetry of the plasma divertor flows in the U-3M torsatron is confirmed [3]. Due to the characteristic properties of the device, such as enclosing the whole magnetic system into a large vacuum chamber, a specific structure of the edge field lines ensuring
the helical divertor magnetic configuration and the method of RF plasma production and heating with the antenna placed in a short section of the torus, strong toroidal and radial inhomogeneities are inherent to the peripheral plasma in U-3M. Unlike the Vf, ne and Te spatial distributions far from the antenna, the distributions of these parameters close to the antenna, as well as
their absolute values, are strongly disturbed by the near antenna field.
[1] О.М. Shvets, I.A. Dikij, S.S. Kalinichenko, A.I. Lysojvan, et al. Nucl. Fusion 26 (1986) 23.
[2] V.V. Chechkin, L.I. Grigor’eva, R.O. Pavlichenko, et al. Plasma Phys. Reports 40 № 8 (2014) 601.
[3] V.V.Chechkin, L.I. Grigor’eva, M.S. Smirnova, et al. Nucl. Fusion 42 192 (2002).
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
69
PA–12
RADIAL PROFILE OF THE ELECTRON ENERGY DISTRIBUTION FUNCTION IN
RF CAPACITIVE GAS DISCHARGE PLASMA
M. Dimitrova1, N. Puac2, N. Skoro2, K. Spasic2, G. Malovic2, Tsv. Popov3, F. Dias4,
Z. Lj. Petrovic2
1
Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko
Chaussee blvd., 1784 Sofia, Bulgaria
2
Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
3
Faculty of Physics, St. Kliment Ohridski University of Sofia, 5, J. Bourchier Blvd., 1164
Sofia, Bulgaria
4
Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, 1049-001 Lisboa, Portugal
Low temperature (non-equilibrium) plasmas are the basis for a number of technologies, old,
current and future. The success story is, of course, plasma etching, which, together with photolithography, is the basis for miniaturization of integrated circuits; other major applications include surface alloying, thin film deposition, plasma displays, modification of the properties of
polymers and organic materials. Recently, the most promising seems to be the field of plasmabased medical applications. Non-equilibrium plasmas are difficult to describe by universal
theories, so that joint efforts are needed in diagnostics and modelling in order to understand
their properties and use that knowledge to control, design and optimize applications. The importance of the research is that it will facilitate applications while maintaining the scientific
effort on the fundamental aspects of non-equilibrium plasmas: the relative simplicity of the experiments makes them excellent tools in studying non-equilibrium plasmas.
This paper reports experimental results on a low-pressure argon capacitive RF discharge at
different conditions, as gas pressure in the range 3 ÷ 30 Pa and different power 10 ÷ 100 W. The
measured IV characteristics were processed by two different second derivative probe techniques for determination of the plasma parameters and the electron energy distribution function. The radial profile of the main plasma parameters are presented.
Acknowledgements: This research has been supported by the JOINT RESEARCH PROJECT
between the Academy of Sciences and Arts of Serbia and the Institute of Electronics BAS BG.
PA–13
POWER FLUX DENSITY IN THE DIVERTOR REGION OF THE COMPASS
TOKAMAK IN OHMIC ELMY H-MODES
M. Dimitrova1,2, V. Weinzettl1, J. Matejicek1, Tsv. Popov3, S. Marinov3, S. Costea4, R.
Dejarnac1, J. Stöckel1, J. Havlicek1, R. Panek1 and the COMPASS team
1
Institute of Plasma Physics, Academy of Sciences of the Czech Republic,
3, Za Slovankou, 182 00 Prague 8, Czech Republic
2
Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences,
72, Tsarigradsko Chaussee, 1784 Sofia, Bulgaria
3
Faculty of Physics, St. Kliment Ohridski University of Sofia,
5, J. Bourchier blvd., 1164 Sofia, Bulgaria
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
70
4
Institute for Ion Physics and Applied Physics, University of Innsbruck,
25 Technikerstr., A-6020 Innsbruck, Austria
We report experimental results obtained by Langmuir probes embedded in the divertor tiles on
the COMPASS tokamak. Measurements of the current-voltage (IV) probe characteristics were
performed during ohmic ELMy H-modes in deuterium plasmas, toroidal magnetic field
BT = 1.15 T, plasma current Ip = 300 kA and line-averaged electron density ne = 5×1019 m−3.
The data obtained between the ELMs were processed by the recently published first-derivative
probe technique for precise determination of the plasma potential and the electron energy
distribution function (EEDF) [1,2].
The spatial profile of the electron temperature shows that the EEDF at the high-field side is
Maxwellian with a temperature of 6 − 10 eV; however, in the private flux region it differs from
the Maxwellian but can be approximated by a bi-Maxwellian distribution.
The electron temperatures and densities obtained were used to evaluate the radial distribution
of the parallel power flux density as being of the order of 0.05 − 9 MW/m2, and the electron
pressure, 0.3 − 40 Pa.
The experimental conditions were used to investigate the plasma interaction with tungsten
samples, with or without pre-grown He fuzz. The samples were observed by using the fast
framing Photron APX camera with the aim to trace ELM-induced arcs on the sample surface
and estimate a critical power flux for an arc production depending on different surface
properties.
Acknowledgements: This research has been supported by the Czech Science Foundation grant
No. 14-12837S, by the International Atomic Energy Agency (IAEA) Research Contract No
17125/R0, R1 and R2 as a part of the IAEA CRP F13014 on “Utilisation of a Network of
Small Magnetic Confinement Fusion Devices for Mainstream Fusion Research”, by the JOINT
RESEARCH PROJECT between the Institute of Plasma Physics v.v.i., AS CR and the Institute
of Electronics BAS BG; and by MSMT Project # LM2011021.
References
[1] Popov Tsv K et al, Plasma Phys. Control. Fusion 51 (2009), 065014
[2] Dimitrova M et al, Contrib. Plasma Phys. 54 No. 3 (2014) 255
PA–14
ELECTRON ENERGY DISTRIBUION FUNCTION IN THE DIVERTOR REGION OF
THE COMPASS TOKAMAK
M. Dimitrova1,2, E. Hasan2,3, P. Ivanova2, E. Vasileva2, Tsv. Popov3, R. Dejarnac1, J. Stöckel1,
R. Panek1 and the COMPASS team
1
Institute of Plasma Physics, Academy of Sciences of the Czech Republic,
3, Za Slovankou, 182 00 Prague 8, Czech Republic
2
Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences,
72, Tsarigradsko Chaussee, 1784 Sofia, Bulgaria
3
Faculty of Physics, St. Kliment Ohridski University of Sofia,
5, J. Bourchier blvd., 1164 Sofia, Bulgaria
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
71
The plasma parameters during an L-mode hydrogen discharge in the COMPASS tokamak with
a toroidal magnetic field BT =1.15 T and a line-averaged electron density ne = 6×1019 m−3 and
with a plasma current variation from 209 kA to 100 kA were studied in the divertor region. It is
shown that as the plasma current decreases, the position of the outer strike point changes within
a few millimeters. In contrast, the position of the inner strike point is shifted towards the highfield side by about 5 cm. The electron energy distribution function (EEDF) for 209 kA at the
high-field side and the private region is Maxwellian with a temperature in the range of 5 9 eV, while around the outer strike point and the low-field side it is bi-Maxwellian with a lowenergy electron group (4 - 5 eV) and higher energy electrons (10 - 20 eV). As the plasma
current decreases, the appearance of the bi-Maxwellian EEDF is shifted towards the low-field
side; at a plasma current of 100 kA the EEDF is Maxwellian in the whole divertor region.
Acknowledgements: This research has been supported by the International Atomic Energy
Agency (IAEA) Research Contract No 17125/R0, R1 and R2 as a part of the IAEA CRP
F13014 on “Utilisation of a Network of Small Magnetic Confinement Fusion Devices for
Mainstream Fusion Research”, by the JOINT RESEARCH PROJECT between the Institute of
Plasma Physics v.v.i., AS CR and the Institute of Electronics BAS BG; by a project BG051
PO001-3.3.06-0057 and by MSMT Project # LM2011021.
PA–15
RADIAL PROFILE OF THE PLASMA PARAMETERS MEASURED BY A
HORIZONTAL RECIPROCATING LANGMUIR PROBE IN THE COMPASS
TOKAMAK
P. Ivanova1, M. Dimitrova1,2, Tsv. K. Popov3, D. López-Bruna4, P. Vondráček2, R. Dejarnac2,
J. Stöckel2, M. Aftanas2, P. Böhm2, P. Bílková2, M. Hron2 and R. Panek2
1
Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences,
72, Tsarigradsko Chaussee blvd,, 1784 Sofia, Bulgaria
2
Institute of Plasma Physics, Academy of Sciences of the Czech Republic,
3, Za Slovankou, 182 00 Prague 8, Czech Republic
3
Faculty of Physics, St. Kliment Ohridski University of Sofia, 5, J. Bourchier blvd., 1164
Sofia, Bulgaria
4
Laboratorio Nacional Fusión, CIEMAT, Complutense 40 – 28040 Madrid, Spain
The radial distribution of the main plasma parameters in the scrape-off-layer of the COMPASS
tokamak was studied in an L-mode regime using a new electrical probe mounted on a
horizontal manipulator. The new probe head consists of two probe tips: one is oriented parallel,
and the other, perpendicular to the magnetic field lines. The radial profiles of the plasma
potential and the electron energy distribution functions, i.e., the electron temperatures and
densities, were derived from the Langmuir probe current-voltage characteristics measured by
applying the first-derivative probe technique (FDPT) [1].
During the experiment, three different shots with accretive average density (density scan) and
three shots with different plasma current (current scan) were studied. The plasma parameters
evaluated by the FDPT using the parallel and the perpendicular probe tips showed satisfactory
agreement. The simplified kinetic solver for neutrals included in the ASTRA package [2] was
used to study the ionization of neutral deuterium atoms in the vicinity of the last closed flux
surface. The influence of the ionization on the formation of the electron energy distribution
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
72
function is discussed [3].
Acknowledgements: This research has been supported by the GACR grant No. P205/11/2341,
by the International Atomic Energy Agency (IAEA) Research Contract No 17125/R0, R1 and
R2 as a part of the IAEA CRP F13014 on “Utilisation of a Network of Small Magnetic Confinement Fusion Devices for Mainstream Fusion Research” and 7th IAEA Joint Experiment; by
the JOINT RESEARCH PROJECT between the Institute of Plasma Physics AS CR and the
Institute of Electronics BAS BG; and by MSMT Project # LM2011021.
References
[1] Tsv. K. Popov, P. I. Ivanova, J. Stockel and R. Dejarnac, 2009 Plasma Phys. Control.
Fusion 51, 065014 "Electron energy distribution function, plasma potential and electron
density measured by Langmuir probe in tokamak edge plasma"
[2]. Pereverzev G V and Yushmanov P N, 2002 ASTRA Automated System for Transport
Analysis, Tech. Rep. IPP, Max Plank Institut für Plasmaphysik, Garching, February 5/98
[3] Tsv K Popov et al. 2015 Plasma Phys. Control. Fusion (submitted) "Bi-Maxwellian
electron energy distribution function in the vicinity of the last closed flux surface in fusion
plasma"
PA–16
DEVELOPMENT OF PROBLEM-ORIENTED SOFTWARE PACKAGES FOR
NUMERICAL STUDIES AND COMPUTER AIDED DESIGN (CAD) OF
GYROTRONS
M. Damyanova1, S. Sabchevski1, I. Zhelyazkov2, E. Vasileva1, E. Balabanova1, P. Dankov2, P.
Malinov2
1
2
Institute of Electronics of the Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
Faculty of Physics, St. Kliment Ohrdidski University of Sofia, Association EURATOMINRNE,
5, James Bourchier blvd., 1164 Sofia, Bulgaria
Gyrotrons are the most powerful sources of coherent CW (continuous wave) radiation in the
frequency range situated between the long-wavelength edge of the infrared light (far-infrared
region) and the microwaves, i.e., in the region of the electromagnetic spectrum, which is usually called THz-gap (or T-gap) since the output power of other devices (e.g., solid-state oscillators) operating in this interval is by several orders of magnitude lower. In recent years, the
unique capabilities of the sub-THz and THz gyrotrons have opened the road to many novel and
future promising applications in various physical studies and advanced high-power terahertz
technologies. We present the current status of the problem-oriented software packages (most
notably GYROSIM and GYREOSS) used for numerical studies, computer-aided design (CAD)
and optimization of gyrotrons for various applications. They consist of a hierarchy of codes
specialized to modelling and simulation of different subsystems of the gyrotrons (EOS, resonant cavity, etc.) and are based on adequate physical models, efficient numerical methods and
algorithms. The performance of the simulation tools developed is illustrated by results of numerical experiments and benchmarking tests. Finally, we conclude with an outlook for the future elaboration and extension of the computational modules of the underlying computer codes.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
73
PA–17
THERMOPHYSICAL PROPERTIES OF CF4/O2 AND SF6/O2 GAS MIXTURES
M. Damyanova1, U. Hohm2, E. Balabanova1, D. Barton3
1
Institute of Electronics of the Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
2
Institut für Physikalische und Theoretische Chemie der TU Braunschweig,
Hans-Sommer-Str. 10, D-38106 Braunschweig, Germany
3
Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale
Theory and Computation, Westfälische Wilhelms-Universität Münster, Corrensstraße 40,
48149 Münster, Germany
The determination of reliable thermophysical data of pure gasses and gas mixtures is an
important but in many cases cumbersome experimental and computational task. Such data
related to the transport (viscosity, diffusion) and equilibrium (second virial coefficient)
properties are needed in many practical applications. The fluorinated gasses and gas mixtures
e.g. CF4/O2 and SF6/O2 are widely used for dry etching of silicon, some silicides, polymers etc.
[1-3]. Also, there is evidence that the mixture SF6/O2 plays a significant role in studying the
convective and diffusive intrapulmonary gas transport [4].
Despite the intensive use of CF4/O2 and SF6/O2 in practical applications, still little is known
about their thermophysical properties, especially in wide ranges of temperature and
composition.
The aim of this work is to calculate and present recommended values for the viscosity,
diffusion and second virial coefficients of CF4/O2 and SF6/O2 gas mixtures. The calculation of
the transport and virial coefficients of the pure substances CF4, SF6 and O2 is based on an (n-6)
Lennard-Jones temperature dependent potential model, discussed in [5]. In this work we use
our previously suggested Hohm-Zarkova-Damyanova (HZD) mixing rules [6], which have
been shown to yield reasonable interaction potentials between unlike molecules and,
subsequently, reliable thermophysical properties of binary gas mixtures at low pressures. The
data for the viscosity, diffusion and second virial coefficients for both mixtures are obtained in
a wide temperature range between 200 K and 1000 K. We compare our findings to the
available experimental and theoretical data. In general good agreement is observed.
[1] Yu. N. Grigoryev and A. G. Gorobchuk, Russian Microelectronics 36(5) (2007) 321
[2] T. P. Chow and G. M. Fanelli, J. Electrochem. Soc. 132(8) (1985) 1969
[3] J. Meichsner, M. Schmidt, R. Schneider, H. Wagner, Nonthermal Plasma Chemistry and
Physics, CRC Press, (2012)
[4] R. C. Tai, H. Chang, and L. Farhi, Resp. Physiology 40 (1980) 253
[5] L. Zarkova, U. Hohm, and M. Damyanova, J. Phys. Chem. Ref. Data 35(3) (2006) 1331
[6] U. Hohm, L. Zarkova, and M. Damyanova, Int. J. Thermophys. 27(6) (2006) 1725
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
74
PA–18
INTERSUBBAND OPTICAL ABSORPTION IN NITRIDE SUPERLATTICE GROWN
BY MBE
I. Asenova1, E. Valcheva
1
Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 James Bourchier blvd., 1164
Sofia, Bulgaria
We present a theoretical study of the intersubband absorbance of the wurtzite AlN/GaN
superlattice. The structure is characterized by macroscopic in-layer polarization, which breaks
down the symmetry of the potential profile, thus making the parity-based transition rules
invalid. As a result, the “allowed” transitions are shown to be exceeded in intensity by the
“forbidden” ones. All our considerations are made within the assumption that no bias is applied
to the device. The theoretical model we utilize for our calculations is based on the envelopefunction approximation, while the bound state energies of the system are calculated via the
transfer matrix formalism.
PA–19
AUTOMATION OF THE ELECTRON BEAM WELDING PROCESS
E. Koleva1,2, V. Dzharov1, M. Kardjiev1, G. Mladenov1
1
2
Institute of Electronics, Bulgarian Academy of Sciences
University of Chemical Technology and Metallurgy, Sofia
The electron beam has been developed over the years into a flexible and economic
manufacturing tool. Due to the deep penetration in the work-piece, the electron beam is able to
generate a narrow weld with a minimal thermally affected zone and without the usage of
welding consumables. The high-vacuum required by the method prevents the heated and
melted material from being oxidized and affected by atmospheric pollutants. With the
advanced development of computer control, the number of electron-beam applications has
significantly increased. In what concerns the electron-beam welding (EBW) technologies, the
EBW plants were developed into complex equipment containing highly-stabilized power
sources and electronic blocks, a reliable and effective vacuum system, a technologcal chamber
with a precision 3D manipulator, thus becoming truly software controlled programmed
manufacturing tools with high efficiency and excellent reproducibility. The technological data
gathered during the process enable quality monitoring and support the improvement of the
testing process of the manufactured components; also, the data are recorded for future analysis
of the relations of the adjusted process parameters and the weld quality and stability.
In this work, the automatic control is considered of the vacuum and cooling systems of the
equipment located in IE-BAS for electron-beam welding, evaporation and surface
modification, together with the electron-beam formation and motion. A project is developed for
the control and management based on existing and additional technical means of automation.
Optimization of the indicators, which are critical for the time period needed for reaching a
working regime and stopping the operation of the installation, is performed using
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
75
experimentally obtained transient characteristics. The control of the beam formation and the
motion over different trajectories is designed and simulated. The automation of the available
equipment aims to improve its efficiency and the repeatability of the results obtained, as well
as stabilization of the process parameters.
PA–20
ELECTRON BEAM CHARACTERIZATION BY TOMOGRAPHIC APPROACH
E. Koleva1,2, L. Koleva2, D. Todorov, G. Mladenov1
1
2
Institute of Electronics, Bulgarian Academy of Sciences
University of Chemical Technology and Metallurgy, Sofia
The characterization of the radial and angular space distribution of particle trajectories (or the
respective current distributions) in high-power electron beams is an important scientific and
practical task, connected with improving the quality of the electron-beam technologies,
creating standards of electron-beam welding machines and permitting transfer of concrete
electron-beam welding technologies from one equipment to another.
To apply the advantages of electron-beam welding, it is necessary to know the properties of the
electron beam. There only exist standards for measuring the electron-beam current and
accelerating voltage as beam characteristics applicable to the acceptance inspection of an
electron-beam welding machine or to research. These parameters cannot characterize the
quality of the electron-beam produced in terms of the ability to transport it over long distances
and to focus it into a small spot with a minimum divergence.
Tomography is a technique for reconstruction of a two-dimensional object image from a set of
its one-dimensional projections, measured as an array of line integrals (or slices) of the object
studied. This technique is widely used in different scientific areas, starting from medical
applications, materials science etc. There, a Fourier transformation from real to frequency
space and a subsequent back Fourier transformation permit one to reconstruct the beam crosssection current density image (beam radial intensity profile) with its asymmetry features.
During the last decade, measurements were proposed of the profile of intense electron beams
by an enhanced modified Faraday cup. We developed further this tomography evaluation to
obtain the beam emittance, containing the beam current distribution in the cross-section
studied, together with the angular distribution of the beam electrons there. The emittance (or
the reciprocal value − the brightness normalized to one volt) is an invariant quantity along the
beam and could be used as а standard characteristic, for prognosis and optimization, as well as
for transfer of technologies from one electron beam equipment to another.
In this work, based on the tomographic approach, the 3D beam radial current density
distribution is reconstructed and the angular beam distribution and the beam emittance are
estimated when variyng the electron beam parameters: If – focusing current, Ie – beam current,
Uv – venelt voltage and the distance H to the measuring device. By implementing regression
analysis, the dependences of these beam quality characteristics on the electron-beam
parameters are estimated. The tomographic algorithm for beam reconstruction is optimized
through comparison of the simulation results for different experimental equipment sets. A
graphical user interface for visualization and investigation of the electron-beam characteristics
is developed.
76
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
PA–21
VERTICAL PLASMA TURBULENCE SUPPRESSION IN CROSSED ELECTRICAL
AND MAGNETIC FIELDS DUE TO FINITE LIFETIME OF ELECTRONS AND IONS
AND DUE TO FINITE SYSTEM LENGTH
I.P.Levchuk, V.I.Maslov, I.N.Onishchenko, A.M.Yegorov, V.B.Yuferov
NSC Kharkov Institute of Physics & Technology, 61108 Kharkov, Ukraine
The plasma in crossed radial electrical and longitudinal magnetic fields has a rotating drift.
In the case of multicomponent plasma, the plasma column rotation leads to a spatial separation
of the ion component.This principle is a fundamental method for the separation of heavy and
light fractions of the ions in the rotating plasma with a positive potential on the cylindrical axis
of the longitudinal magnetic and radial electric field (the system E×B). The possibility to use
rotating-plasma devices for substance separation promotes the plasma investigations and
development of facilities for substance separation into mass groups and elements. In plasma [13], a turbulence has been excited in crossed radial electrical and longitudinal magnetic fields by
a gradient of the external magnetic field. This turbulence is a distributed vorticity. In this work,
the excitation and damping of similar vortical turbulence, excited in cylindrical plasma in
crossed radial electrical and longitudinal magnetic fields [4], is investigated theoretically. The
dispersion equation was derived describing the instability development of vortex turbulence
excitation in cylindrical plasma in crossed radial electric and axial magnetic fields with taking
into account the longitudinal inhomogeneity and the finite time of the electrons and ions
leaving the plasma. It is shown that the finite length of the system and the finite time of the
electrons and ions leaving the plasma lead to the appearance of an instability threshold and to a
decrease of the rate of its development.
[1] A.Goncharov, A.Dobrovolsky, A.Kotsarenko, A.Morozov, I.Protsenko // Journal «Physica
Plasmy». 1994, v. 20, pp. 499.
[2] A.Goncharov, I.Litovko, Electron Vortexes in High-Current Plasma Lens // IEEE Trans.
Plasma Sci. 1999, v. 27, pp. 1073.
[3] V.I.Maslov, A.A.Goncharov, I.N.Onishchenko, Self-Organization of Non-Linear Vortexes
in Plasma Lens for Ion-Beam-Focusing in Crossed Radial Electrical and Longitudinal
Magnetic Fields // Invited Paper. In Proceedings of the International Workshop "Collective
phenomena in macroscopic systems", G. Bertin, R. Pozzoli, M. Rome' & K.R. Sreenivasan
Eds. World Scientific, Singapore, 2007, pp. 20-25.
[4] V.B.Yuferov, A.S.Svichkar, S.V.Shariy, T.I.Tkachova, V.О.Ilichova, V.V.Katrechko,
A.I.Shapoval, S.N. Khizhnyak, About Redistribution of Ion Streams in Imitation
Experiments on Plasma Separation // Problems of Atomic Science and Technology. Ser.:
Physics of Radiation Damage and Radiation Material. 2013, №5 (87), pp. 100-103.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
77
PA–22
PROVIDING HOMOGENEOUS AND IDENTICAL FOCUSING OF TRAIN OF
SHORT RELATIVISTIC ELECTRON BUNCHES BY WAKEFIELD PLASMA LENS
I.P. Levchuk, V.I.Maslov, I.N.Onishchenko
NSC Kharkov Institute of Physics & Technology, 61108 Kharkov, Ukraine
Focusing relativistic electron bunches by wakefield, excited in the plasma, is important and
interesting (see [1-2]). The focusing of bunches by wakefield, excited in plasma by resonant
train of relativistic electron bunches (the repetition frequency of the bunches ωm coincides with
the plasma frequency ωm = ωp), is inhomogeneous [3, 4]. A mechanism of focusing in plasma,
in which all bunches of train are focused identically and uniformly, has been proposed and
investigated by numerical simulation in [3, 4]. This plasma wake lens for short relativistic
electron bunches is studied in the present work analytically and by numerical simulation by
lcode [5]. Unbound nonmagnetized homogeneous plasma is considered. Rectangular in
longitudinal direction bunches (i.e. the bunch current is constant along the bunch axis) are
considered in a fixed current approximation. We consider homogeneous focusing of train of
short bunches. We show that all bunches of the train are focused identically and uniformly. It is
also shown that there are two wakefield plasma lenses for a train of short bunches. In the first
lens, achieving identical and uniform focusing necessitates that the length of first bunch ∆ξb1
be chosen equal to the half of wavelength ∆ξb1=λ/2; all other bunches should be short,
∆ξb<λ/2, and the charge density of all other bunches should be more than twice as large as the
charge density of the first bunch n1 = ni/2, i = 2, 3, ... In the second lens, achieving identical and
uniform focusing necessitates that the charge density of the first bunch be smaller by a factor of
2 than the charges of the other bunches, and the spatial interval between the first and the
second bunches should be equal to (n+1/8)λ, n = 1, 2, … The intervals between all bunches in
both lenses must be multiples of the wavelength δξ=pλ, p = 1, 2, …, in order to achieve a
longitudinal wakefield Ez = 0 and a radial focusing field Fr =const along the bunch. The first
bunch only is in the finite decelerating field Ez ≠ 0. The other bunches are in a longitudinal
electric field equal to zero Ez = 0. Then, the first bunch only exchanges energy with the
wakefield. The subsequent bunches do not interchange energy with the wakefield and the
amplitude of the wakefield does not change along the train. The radial wake force Fr in the
areas of bunches location is approximately constant along the bunches.
[1] Ya. Fainberg, M. Ayzatsky, V.Balakirev et al., Focusing of Relativistic Electron Bunches at
the Wakefield Excitation in Plasma. Proceedings PAC’97. 12-16 May, 1997 Vancouver, Canada. V. II. P. 651-653.
[2] H. Suky et al., Proc. of PAC. New York, 1999.
[3] K.V.Lotov, V.I.Maslov, I.N.Onishchenko, O.M.Svistun. Problems of Atomic Science & Technology. 2012. №3(79). P. 159-163.
[4] V.I.Maslov, I.N.Onishchenko, I.P. Yarovaya. Problems of Atomic Science & Technology.
2013. №1(83). P. 134136.
[5] K.V.Lotov. Phys. Plasmas. 1998, V. 5, N 3, P. 785-791.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
78
PA–23
MODEL OF SURFACE-WAVE DISCHARGE AT ATMOSPHERIC PRESSURE WITH
FIXED PROFILE OF GAS TEMPERATURE
M. Nikovski1, Zh. Kiss'ovski1, E. Tatarova2
1
Faculty of Physics, St. Kl. Ohridski University of Sofia
5, J Bourchier blvd., 1164 Sofia, Bulgaria
2
Institute of Plasmas and Nuclear Fusion, Instituto Superior Tecnico, University of Lisbon,
1049-001 Lisbon, Portugal
E-mail: mon_1992@abv.bg, kissov@phys.uni-sofia.bg
In this study, a model is presented of a surface-wave sustained discharge at 2.45 GHz at
atmospheric pressure. A small plasma source creates a plasma column in a dielectric tube and a
plasma torch is observed above the top of the tube if the absorbed power is higher than 11 W
[1]. The plasma parameters and the axial profile of the gas temperature change significantly in
the presence of the substrate above the plasma torch. The model includes a dispersion relation
of azimuthally symmetric surface waves in the plasma column in the dielectric tube and in the
plasma torch [2]. The electron Boltzmann equation under local approximation is solved,
together with heavy particle balance equations at a fixed axial profile of the gas temperature
[3]. A detailed collisional-radiative model is developed for an argon discharge at atmospheric
pressure, which includes 21 rate balance equations for excited Ar atoms [(Ar(1s5-1s1), Ar(2p10 2p1), Ar(2s3d), Ar(3p)], for positive Ar+ and Ar2+ ions and for excited molecules [4]. The
changes in the EEDF shape and the mean electron energy along the plasma column are investigated and the axial structures of the discharge and torch regions are obtained.
[1 ] Kiss’ovski Zh, Ivanov A, Kolev M, Lishev St, Koleva I (2009) J Phys.D: App. Phys 42
182004-10
[2] D. Tsyganov, N. Bundaleska, E. Tatarova, C.M. Ferreira, (2013) Int. J of Hydrogen Energy
38 (2013) 14512-14530
[3] J Henriques, A Ivanov, Zh. Kiss’ovski, E Tatarova, C. M. Ferreira, Bulletin of APS (2011),
64th Annual GEC, v. 56, N 15, p 35
[4]. Kiss’ovski Zh , Ivanov A., Iordanova S and Koleva I 2011 J Phys. D: Appl. Phys., 44,
205203
PA–24
STRAY MAGNETIC FIELD INFLUENCE ON THE CPT RESONANCE
IN A COATED Rb VACUUM CELL
E. Taskova, E. Alipieva and G.Todorov
Academician Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria
The interaction of a resonant laser beam with an atomic absorption medium creates population
redistribution and interference between the atomic levels. This anisotropy of the medium is ex-
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
79
perimentally observed as coherent population trapping (CPT) or electromagnetically induced
transparence (EIT) [1]. Due to the small sub-natural width of the CPT and EIT resonances they
find wide application in metrology, quantum optics, atom cooling.
In this work we present a systematic investigation of the influence of the stray magnetic fields
(MF) on the CPT resonances obtained on Zeeman sublevels of D1 line of 87Rb in a paraffincoated vacuum cell. The cell coating preserves the coherence created in the atomic media.
Consequently, the CPT resonance registered is some orders of magnitude narrower than the
one obtained in a cell without coating. The non-compensated magnetic field which is able to
destroy or change dramatically the CPT resonance shape is in the range of some mG.
Figure 1 shows the shape of the CPT resonance in the presence of a stray magnetic field (red
line) and when the stray magnetic field is compensated (black line). The population, longitudinal and transverse alignment contribute to the fluorescence signal.
The influence of the stray MF on each of
these components is modeled by a standard
semiclassical description of the atomic
system by the statistical operator in density
matrix representation. The irreducible tensor
operator (ITO) formalism program for
numerical modeling of this effect is used.
The numerical calculations are based on the
model presented in [2]. The comparison of
the obtained theoretical line shape of the
resonances with the experiments shows
good agreement.
Figure 1. Influence of stray MF on the CPT resonances
shape; (a) with stray MF and (b) without stray MF.
[1] E.B. Alexandrov, M.P. Chaika, G.I. Hvostenko “Interference of atomic states,” SptingerVerlag (1991).
[2] V. Polischuk, V.Domelunksen, E. Alipieva, G. Todorov, “Modelling of nonlinear interaction of 87Rb atoms with polarized radiation”, Bulg. J. Phys. 39 150-164 (2012).
Acknowledgements: This work has received partial funding from the 7th EU Framework
Programme: "Coherent optics sensors for medical applications-COSMA" (Grant Agreement
No: PIRSES-GA-2012-295264).
PA–25
A SELF-CONSISTENT ONE-DIMENSIONAL MULTIFLUID MODEL OF THE
PLASMA-WALL TRANSITION IN THE PRESENCE OF TWO SPECIES OF
NEGATIVELY BIASED PARTICLES
T. Gyergyek1,2, J. Kovačič2
1
University of Ljubljana, Faculty of Electrical Engineering,
Tržaška 25, 1000 Ljubljana, Slovenia
2
Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
80
The plasma-wall transition in the presence of either negative electrons or energetic electron
population is a subject of great interest and is still an area of very active research in magnetized
[1,2] as well as non-magnetized plasmas [3,4]. An approach that is used by many authors [1-4]
is to assume that the continuity and momentum exchange equations are valid for the positive
ions, while the Boltzmann relation is assumed for the negative particles. In this work, each of
the three particle species present in the plasma is treated by its own pair of continuity and
momentum exchange equations. In this sense, the model is fully self-consistent, since there is
no an a-priori assumption on the density of any of the particle species. There are two negative
and one positive particle species present in the plasma. The model is one dimensional. A set of
seven ordinary differential equations is derived and solved numerically. The solutions give the
density and fluid velocity profiles for all particle species as well as the potential and electric
field profile. Elastic collisions between different particle species can be taken into account. The
same model can be used for the analysis of either plasma with two-electron temperature
distributions, or electronegative plasma that contains electrons and negative ions. Some basic
properties of the model are illustrated and the role of collisions and consistency of the source
terms is investigated. The Bohm criterion under various conditions is obtained.
[1] K. Yasserian, M. Aslaninejad and M. Ghoraneviss, Phys. Plasmas, 16, 023504 (2009).
[2] M. M. Hatami and B. Shokri, Phys. Plasmas, 20, 033506 (2013).
[3] J. I. Fernandez Palop, J. Ballesteros, M. A. Hernandez and R. Morales Crespo, Plasma Sources Sci.
Technol. 16, S76–S86 (2007).
[4] J. I. Fernandez Palop, J. Ballesteros, M. A. Hernandez and R. Morales Crespo, J. Appl. Phys. 91,
2587-2593 (2002).
PA–26
OPEN DSS SIMULATIONS OF POWER FLUCTUATIONS INDUCED BY A
ROOFTOP PV GENERATOR ON A BUILDING LV ELECTRICAL GRID
Hristo Nichev, Miroslav Petrov, Konstantin Lovchinov, Nikolay Tyutyundzhiev
Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences
72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
The high extent of proliferation of photovoltaic (PV) installations in urban areas raises the
problem of power quality and voltage stability during external atmospheric fluctuations. If not
properly designed, densely populated PV installations, connected in a remote node of the grid,
may degrade the power quality or multiply the power fluctuations. A computer simulation of
power flows in a bidirectional grid can reveal weak points in the grid. It can imply measures
for mitigation of fluctuations and creation of algorithms for energy management of future
“smart grids”.
This report gives and overview of the bilateral impact between a decentralized generator and a
LV grid. Daily profiles of the electrical load in a building and the generated power are extracted from grid monitoring devices. Based on experimental data, software simulations are
performed in an open DSS environment − an open-source simulation tool.
Keywords: Photovoltaic systems, PV power generation, Impact on grid stability, Smart grids.
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
PB–10
LASER NANOSTRUCTURING OF Ag FILMS
DEPOSITED ON DIFFERENT SUBSTRATES
Ru. G. Nikov, N. N. Nedyalkov, P. A. Atanasov
POSTER SESSION B:
SURFACES AND THIN FILMS PROCESSING
AND ANALYSIS
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
83
PB–1
PLASMA INDUCED HEATING OF THE SUBSTRATE DURING MAGNETRON
SPUTTERING
S. Muhl, J. Cruz, J. Restrepo
Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Cd.
Universitaria, Av. Universidad 3000, México, DF 04510, México
It is known that the substrate, or more importantly, the surface of the deposit, are heated by the
plasma during magnetron sputtering. However, there have been few detailed reports of this
process, which can involve a combination of bombardment by ions, electrons, excited and
neutral species, and absorption of visible and UV radiation. Here we report a study of the
substrate heating during DC magnetron sputtering of a 4” aluminium target as a function of:
the plasma power, the Ar gas pressure and the substrate bias (floating, earthed and negatively
biased). Additionally, we studied the heating during argon-nitrogen reactive sputtering as a
function of the nitrogen concentration.
For sputtering of aluminium, the substrate could reach temperatures greater than 200 oC and
the temperature distribution over the 4” substrate holder was not uniform; the highest
temperatures were found in front of the racetrack and the lowest, at the edge of the target. For
reactive sputtering, the temperature increased strongly for nitrogen concentrations of > 8 %.
Both aluminium and aluminium nitride thin films were deposited using the sputtering
conditions studied, and the coating characteristics depended on where the substrate was
located. The properties of the films were analyzed using SEM and X-ray diffraction and the
film thickness was measured using a stylus profilometer.
PB–2
INVESTIGATION OF RESISTIVE PROPERTIES OF HTS/MANGANITE BILAYERS
T. Nurgaliev1, B. Blagoev2, V. Strbik3, S. Chromik3, M. Sojkova3
1
Institute of Electronics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria
2
Institute of Solid State Physics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria
3
Institute of Electrical Engineering, Slovak Academy of Sciences,
Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
Manganites show a broad spectrum of physical properties and frequently demonstrate a
coexistence of the spatially separated different electronic and magnetic states at the same time.
The electromagnetic properties of high temperature superconducting (HTS) YBa2Cu3O7-x
(YBCO) depend strongly on the oxygen content x in the CuO chains; depending on x, the
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
84
YBCO can be in insulating antiferromagnetic or in superconducting states. The characteristics
of both materials are very sensitive to the influence of external factors, such as temperature,
magnetic field, stresses and strains. A variety of additional new effects arises in
HTS/manganite heterostructurs due to different coupling mechanisms across the interface.
In this work we considered peculiarities of the resistive characteristics of the manganite
(La0.7Ca0.3MnO3 (LCMO), La0.7Sr0.3MnO3 (LSMO)) films and HTS/manganite
(YBCO/LCMO, YBCO/LSMO) bilayers deposited on different substrates. In particular, LSMO
films sputtered onto LaAlO3 (LAO) substrates with a strip-like twin structure demonstrated
anisotropy of the resistance at room temperatures. The conductive properties of the bilayers are
determined by the contribution of the conductivities of the individual HTS and manganite
layers and by the interaction peculiarities of the layers in the interface. Modeling allowed us to
obtain additional information on the characteristics of the individual layers of the bilayer
structures.
PB–3
TRANSPORT PROPERTIES OF YBa2Cu3Ox/La0.67Sr0.33MnO3 NANOJUNCTIONS
V. Štrbík, Š. Beňačka, Š. Gaži, M. Španková, V. Šmatko,, Š. Chromik, N. Gál, M. Sojková and
M. Pisarčík
Institute of Electrical Engineering, Slovak Academy of Sciences, Bratislava, Slovakia
A metallic ferromagnet (F) in a close proximity with a superconductor (S) can transport
supercurrent over a long distance (long-range proximity effect, LRPE) through conversion of
opposite-spin singlet Cooper pairs (CP) into equal-spin triplet CP, which are not broken by the
exchange energy of F. The optimal conditions for the conversion are still not clear; however, it
is accepted that key points in this process include high interface transparency and magnetic
inhomogeneity at the SF interface. The objects of our contribution are SF nanostrips (a length
of about 1500 nm and a width of about 300 nm) and lateral SFS nanojunctions based on high
critical temperature YBa2Cu3Ox (YBCO) and half-metallic La0.67Sr0.33MnO3 (LSMO) thin
films. We applied a Ga+ focused ion beam for patterning SF nanostrips, as well as SFS
nanojunctions, after removing part of the YBCO film in a slot of width of less than 50 nm. The
temperature dependences of the samples resistance R(T) show a critical temperature TCn ≈ 89 K
of the SF nanostrips; however, the SFS junctions at T < TCn show a residual resistance
R < 100 Ω, corresponding to dirty LSMO (ρ ≈ 10-3 Ω cm) present in the slot; therefore, the
LRPE was not present in the SFS junctions until now. Progress in these investigations will be
presented.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
85
PB–4
FABRICATION OF HYBRID THIN FILM STRUCTURES FROM HTS AND CMR
MATERIALS
M. Sojková1, V. Štrbík1, Š. Chromik1, M. Španková1, T. Nurgaliev2, B. Blagoev2
1
Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9,
841 04 Bratislava, Slovakia
2
Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee,
1784 Sofia, Bulgaria
Perovskite materials (high-temperature superconductor (HTS) and half-metallic ferromagnetic
manganite with colossal magnetoresistance (CMR)) demonstrate a number of interesting
properties from both theoretical and application points of view, including the spin-polarized
DC current injection effect from a ferromagnetic CMR to a HTS film. As HTS we used
YBa2Cu3Ox (YBCO) and Tl2Ba2Ca1Cu2Ox (TlBCCO) thin films, and as CMR, La1-xSrxMnO3
(LSMO) or La1-xCaxMnO3 (LCMO), all with a nominal thickness in the range of 50-300 nm.
The films were prepared by magnetron sputtering, laser pulsed ablation techniques, and in the
case of TlBCCO, by a two-step thallination process. The hybrid HTS/CMR structures were
fabricated using wet etching and “lift-off” processes. We will present some structural and
electrical properties of the HTS/CMR heterostructures.
PB–5
PROPERTIES OF NANOSECOND LASER PROCESSED
POLYDIMETHYLSILOXANE (PDMS)
P.A. Atanasov1*, N.E. Stankova1, N.N. Nedyalkov1, T.R. Stoyanchov1, Ru.G. Nikov1,
N. Fukata2, J. W. Gerlach3, D. Hirsch3, B. Rauschenbach3
1
Institute of Electronics, Bulgarian Academy of Sciences,
72 Tsaridradsko Chaussee blvd., Sofia 1784, Bulgaria.
2
International Center for Materials for NanoArchitectonics (MANA),
National Institute for Materials Science (NIMS), 1-1Namiki, Tsikuba 305-0044, Japan
3
Leibniz Institute of Surface Modification (IOM),
Permoserstrasse 15, D-04318 Leipzig, Germany
*
paatanas@hotmail.com
Medical grade polydimethylsiloxane (PDMS) elastomer is a widely used biomaterial in medicine and for preparation of high-technology devices because of its remarkable properties: mechanical flexibility and stability; high dielectric constant and breakdown field; optical transparency in the ultraviolet (UV) – visible (VIS) spectral regions; biocompatibility and biostability;
simple and inexpensive fabrication. High-definition tracks and electrodes can be fabricated by
UV or VIS ns- or fs-laser pulse processing with subsequent metallization in order to get alterations of the chemical composition and structural morphology of the ablated traces. The importance of knowing the changes of the morphology, structure and chemical properties of the laser-processed material will help to understand the nature of the laser-matter interaction.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
86
In this work, we present experimental results on the change of the morphology, chemical composition and structure of the PDMS processed by UV, VIS and IR ns-laser pulses. The
processing of medical grade PDMS elastomer is accomplished using the fundamental
(λ = 1.064 µm), 2nd HG (λ = 532 nm) or 4th HG (λ = 266 nm) of a Q-switched Nd:YAG laser
(pulse duration τ = 15 ns and repetition rate of 10 Hz). The as-processed material is studied by
XRD, SEM, µ-Raman analyses and 3D laser microscopy in order to get information for the influence of the different processing parameters as laser wavelength, fluence and number of consecutive pulses on its properties.
Key words: PDMS-elastomer, optical properties; UV, VIS, and IR ns-laser processing; XRD,
µ-Raman, XPS, SEM analyses and 3D laser microscopy;
PB–6
PREPARATION AND CHARACTERIZATION OF COPPER CATALYSTS
SUPPORTED ON MESOPOROUS SILICA-CARBON NANOCOMPOSITES
G. Atanasova1, N. Stoeva 1, R. Nickolov2, I. Spassova1
1
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia,
Bulgaria
2
University of Chemical Technology and Metallurgy, Sofia, 1756 Sofia, Bulgaria
In view of better catalytic performance, enhanced activity and selectivity, the composite
catalysts are of interest and have been extensively studied recently in the field of heterogeneous
catalysis. These composite catalysts, prepared by one or more active components supported on
a support are of interest because of the possible interaction between the catalytic components
and the support materials that could ensure the preparation of composite catalysts with much
improved properties. In this case, it is important to study the possible cooperation in the
nanocomposite catalysts between the different catalytic components or between the catalytic
components and the support.
Mesoporous silica-carbon nanocomposites have drawn more attention because of the
combination of multi-functionality, well-controlled pore structure, high surface areas, tuneable
pore morphology facilitating the diffusion of the reagents and the reaction products inside the
pores. Mesostructured silica-carbon nanocomposites were prepared by tri-constituent coassembly of previously prepared resol (phenol-formaldehyde clay), silica oligomers from acidcatalysed hydrolysis of TEOS, and triblock copolymer Pluronic F127 via the EISA method in
ethanol solution. The composites were synthesized with various silica: carbon ratios using
different quantities of TEOS and resol. The copper active phase was loaded on the supports by
vacuum evaporation of CuCO3Cu(OH)2 in ammonia with subsequent thermal treatment in
argon.
The catalysts were characterized by XRD (low-angle and wide-angle), XPS, TEM, AAS and
low-temperature nitrogen adsorption. A relationship was found between the composition of the
support and the specific surface area, total pore volume, mean pore diameter. XPS
investigations proved the cooperation between the support and the supported copper phases in
order how the support maintains the active catalyst phase. It was found that different silica:
carbon ratios in the composites provoke different Cu+ and Cu2+ content on the surface.
Acknowledgments: The work was financed by the National Science Fund Project E02/22014.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
87
PB–7
THIN NANOCRYSTALLINE ZIRCONIA FILMS PREPARED BY PULSED LASER
DEPOSITION
A.Og. Dikovska1*, G.B. Atanasova2, G.V. Avdeev3
1
Institute of Electronics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee blvd., Sofia 1784, Bulgaria
2
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences,
Acad. G. Bonchev str., bl. 11, 1113 Sofia, Bulgaria
3
Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences,
Acad. G. Bonchev str., bl. 11, 1113 Sofia, Bulgaria
Zirconium oxide (ZrO2) is a transition metal oxide, which offers several interesting technological applications due to its properties, such as high melting point, high refractive index, good
thermal, chemical and mechanical stabilities, wide band gap, high dielectric constant and electrical resistivity. It finds applications in optical coatings, protective coatings and insulating layers, catalyst for alcohol synthesis, in fuel cells as well as in thermal barrier coatings. ZrO2 has
three well-defined polymorphs under different conditions of temperature: monoclinic, tetragonal and cubic. These high temperature phases can be retained at room temperature by doping
with some suitable oxides, such as aluminium oxide, yttrium oxide, magnesium oxide, and calcium oxide.
In the present work, zirconia thin films were prepared on different (silicon, quartz, and steel)
substrates by the PLD technique at different substrate temperatures and partial oxygen pressures. The substrate temperature was varied from room to 600 oC, and the oxygen pressure,
from vacuum to 0.1 mbar. The effect of the substrate temperature and oxygen pressure on the
formation of m-zirconiaand t-zirconia phases was investigated by Raman spectroscopy. The
formation of a cubic phase of ZrO2 was also investigated. The variation in the optical properties was studied and discussed in relation with the microstructure of the zirconia films.
PB–8
EFFECT OF AL2O3 ON THE LOW TEMPERATURE DEGRADATION OF Y-PSZ
THIN FILMS
A.Og. Dikovska1*, G.V. Avdeev2, G.B. Atanasova3
1
Institute of Electronics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee blvd., Sofia 1784, Bulgaria
2
Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences,
Acad. G. Bonchev str., bl. 11, 1113 Sofia, Bulgaria
3
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences,
Acad. G. Bonchev str., bl. 11, 1113 Sofia, Bulgaria
*g_avdeev@abv.bg
Zirconia is one of the most important structural ceramics. In particular, yttria partially stabilized zirconia (Y-PSZ) with excellent mechanical properties have been widely used in many
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
88
industrial fields. However, the phase transformation from tetragonal (t) to monoclinic (m) occurring on the surface of Y-PSZ at the low temperatures of 100 ~ 400 C usually produces micro-cracks and macro-cracks and results in an abrupt decrease in strength. This is called lowtemperature degradation, which seriously affects the application of Y-PSZ. The research on
improving the degradation resistance of Y-PSZ has lately made considerable progress. For example, controlling the grain size, doping by metal oxides and stabilizing by surface engineering
technologies, are effective techniques improving the degradation resistance of Y-PSZ. Adding
particles with a high elastic modulus to Y-PSZ has been considered as one of the most accessible techniques for inhibiting the low temperature degradation. It has been indicated that adding
Al2O3 particles into Y-PSZ not only improves its mechanical properties at room temperature,
but also inhibits the low-temperature degradation.
In this work, zirconia and zirconia composites were prepared in thin-film form by pulsed laser
deposition (PLD). The microstructure, phase composition, and tetragonal to monoclinic transformation behavior were investigated and discussed as a function of the Al2O3 content. A study
is presented of the low-temperature degradation, called also ageing phenomenon, in zirconiaalumina films. The influence of the yttria content in zirconia composites and microstructure on
the ageing mechanisms is also discussed.
PB–9
INVESTIGATION OF THE AGING PROCESS OF NOBLE METAL NANOSTRUCURES
FABRICATED BY NANOSECOND LASER ABLATION IN WATER
R.G. Nikov1, A.S. Nikolov1, N.N. Nedyalkov1, E.L. Pavlov1, P.A. Atanasov1, M.T.
Alexandrov2, D.B. Karashanova3
1
Institute of Electronics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee blvd., Sofia 1784, Bulgaria
2
Institute of Experimental Pathology and Parasitology, Bulgarian Academy of Sciences,
G. Bonchev Street, bl. 25, Sofia 1113, Bulgaria
3
Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences,
G. Bonchev Street, bl. 109, Sofia 1113, Bulgaria
Colloids of noble metal nanostructures were produced by pulsed laser ablation of solid targets
in water. The fundamental (λ = 1064 nm) and the second (λ = 532 nm) harmonics of a
Nd:YAG laser system were utilized in the ablation process. The colloids produced were stored
in a cuvette at a constant temperature during the ageing process. The changes in the volume of
the colloids produced were studied by measuring the optical extinction spectra. These spectra
were taken at different heights of the cuvette and their changes at different time periods after
fabrication were traced. They were used to assess the ageing process of the colloids expressed
in sedimentation and aggregation of the nanostructures. To visualize the effect of these two
processes, transmission electron microscopy was used. Ultrasonic treatment of the colloids was
applied to achieve modification of the already created clusters and recover the optical
properties of the colloids as closely as possible to these on the day of preparation. As a result,
some of the aggregates were completely disintegrated while others fragmented into smaller
ones. The aim was to establish the optimal storage conditions of the colloids in view of
preserving their original characteristics.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
89
PB–10
LASER NANOSTRUCTURING OF Ag FILMS DEPOSITED ON DIFFERENT
SUBSTRATES
Ru.G. Nikov1, N.N. Nedyalkov1, P.A. Atanasov1
1
Institute of Electronics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee blvd., Sofia 1784, Bulgaria
This paper presents results on nanostructuring of Ag thin films by a laser-assisted technique.
The thin films are fabricated by on-axis pulsed laser deposition technology on glass, metal and
polymer substrates. The as-deposited films are then irradiated by nanosecond laser pulses delivered by a Nd:YAG laser system operated at λ = 355 nm. The characteristics of the film modifications obtained are also studied as a function of the laser pulse parameters and the film
thickness. Under certain conditions, the laser treatment may lead to a decomposition of the Ag
film into a discrete nanostructure on the substrate composed of nanoparticles. The optimal conditions for fabrication of nanoparticles with a narrow size distribution on the different substrates are defined. The modification of the film morphology is studied by means of scanning
electron microscopy of the sample surface. The optical properties study based on structure’s
transmission spectra shows that film decomposition into nanoparticles results in a clear dip in
the spectra. This effect is related to efficient plasmon excitation. The shape and position of the
plasmon band are found to depend on both the laser processing parameters and the substrate
material. The fabricated structures can be used in the design of plasmonic solar cells, sensors
and SERS devices.
PB–11
LASER-INDUCED OPTICAL PROPERTIES CHANGES IN GOLD-DOPED
MATERIALS
N.Nedyalkov1,2, M. Koleva2, R. Nikov2, Y. Nakajima1, A. Takami1, M. Terakawa1
1
Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi Kohoku-ku, Yokohama-shi Kanagawa-ken, 223-8522, Japan
2
Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee,
1784 Sofia, Bulgaria
This work presents results on laser processing of Au doped oxide thin films. Using a pulsed
laser deposition technique, SiO2/Au and Al2O3/Au thin films are deposited. The rotating target
used for deposition consists of two sectors containing the oxide material and gold. By changing
the area of the sectors, films with different content of gold are obtained. The deposited films
are then irradiated by laser pulses with different parameters – wavelength, fluence, pulse duration, number of pulses. The optical properties of the processed areas are studied on the basis of
their transmission spectra. It is shown that under certain processing conditions the laser irradiation induces clear coloring and a dip in the transmission spectra of the initially transparent
films. The analyses performed based on TEM, SEM, XRD, and EDX, show that this effect is
related to the formation and dynamics of gold nanoparticles caused by the interaction with the
laser pulses. The influence of the processing condition on the characteristics of the formed particles and the mechanism of their formation are discussed. The structures fabricated can be applied to the design of new optical materials and in plasmonics.
90
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
PB–12
LASER-ASSISTED PROCESSING OF THE PDMS ELASTOMER AS A MATERIAL
FOR PRECISE NEURAL INTERFACE ENGINEERING
N.E. Stankova, P.A. Atanasov, Ru.G. Nikov, R.G. Nikov, N.N. Nedyalkov
Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd., Sofia
1784, Bulgaria
Direct laser writing based on nanosecond laser processing of the PDMS elastomer has been
performed for production of stretchable micro-channels with high structuring accuracy for
MEMS, NEMS and MEAs devices. This technology could especially facilitate a highresolution, high-density integrated system solution for neural and muscular surface interfacing.
Systematic experiments have been conducted to characterize how the laser beam parameters
(wavelength, fluence, and number of pulses) affect the optical properties and the chemical
composition in the laser treated areas. Remarkable changes of the optical properties and the
chemical composition have been observed. Despite the low optical absorption of the native
PDMS for UV, VIS and NIR wavelengths, successful laser treatment has been accomplished
due to the incubation process occurring below the polymer surface. By increasing the fluence
and the number of pulses, chemical transformations have been revealed in the entire laser
treated area. The incubation reaches saturation after a certain number of pulses and efficient
laser ablation of the material begins. This process is a complex function of the wavelength,
fluence, number of pulses and the material properties as well.
Also, a laser lift-off (LLO) process has been employed to fabricate micro-channeled Au, Ni,
and Pt electrodes. This method could increase the electrical conductance of the as-produced
electrodes, hence, improve the capacitive components of the electrode-tissue interface
interaction.
PB–13
STUDY OF BARIUM HEXAFERRITE NANOSTRUCTURES PRODUCED BY LASER
ABLATION IN WATER
A. Nikolov1, T. Koutzarova1, R. Nikov1, N. Nedyalkov1, N. Stankova1, S. Kolev1, P. Peneva1,
D. Karashanova2 and D. Kovacheva3
1
Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, Sofia
1784, Bulgaria
2
Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences, Acad. G.
Bonchev str., bl. 109, 1113 Sofia, Bulgaria
3
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. Georgi
Bonchev str., bl. 11, 1113 Sofia, Bulgaria
The method of nanosecond pulsed laser ablation in liquid is employed to produce nanostructures of barium hexaferrite. The target fabricated by sol-gel auto-combustion is immersed in
double distilled water. A Nd:YAG laser system is used for the ablation procedure. Different
colloids are fabricated by variying the laser wavelength and fluence. The influence of these
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
91
technological parameters on the morphology of the nanostructures produced is investigated.
The fundamental (λ = 1064 nm), second (λ = 532 nm), third (λ = 355 nm) and fourth (λ = 266
nm) harmonics were used in the experiments, with the and fluence being changed from several
J/cm2 to tens of J/cm2. The stability of the colloids during their ageing is also investigated. The
optical transmission of the colloids in the near UV and visible regions was measured to estimate the effiency of the ablation procedure. Their stability during the ageing process is also
investigated. The shape of the nanostructures and their size distribution are visualized by using
TEM analysis. XRD, SAED and HRTEM are utilized to examine the material phases of the
nanostructures obtained. The nanoscale magnetic ferrites are of particular interest due to their
chemical compatibility with biological tissues and the unique combination of electronic and
magnetic properties.
PB–14
PUMP-PROBE INVESTIGATION OF FEMTOSECOND LASER INDUCED
MODIFICATION OF BIOPOLYMER THIN FILMS
A. Daskalova 1, C. Nathala 2,3, W. Husinsky 2
1
Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee blvd.,
1784 Sofia, Bulgaria
2
IAP, Vienna University of Technology, Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria
3
Femtolasers Productions GmbH, Fernkorngasse10, 1100 Vienna, Austria
Femtosecond lasers can be applied for fast and precise modification of thin biofilms. Previous
studies on surface modification of biopolymers have shown that laser irradiation is a suitable
method for production of thin layer of a porous biomaterial matrix. Structuring the surface of a
biomaterial into arrays with micro- and nanoscale features and architectures defines new
roadmaps to advanced applications of biomaterials in biology and medicine.
The dynamics of the formation of laser-induced surface foam on thin gelatin films upon
irradiation by fs-laser pulses (30 fs pulse duration) is studied by pump-probe experiments.
In order to analyze the influence of temporally distributed energy deposition nn the foam
formation, a Michelson interferometer was used for generating multiple double-pulse
sequences at 800 nm. We explored the possibility of structuring the biopolymer thin film by
applying different time-delays between the separate pulses; the resulting porous morphologies
were characterized by scanning electron microscopy.
This interaction regime allows tailoring of the surface modification by adaptive temporal
separation. We used delay times varying from 0 to 10 ps and a number of pulses from 10-100.
The time-resolved results show that by optimizing the temporal interval between the
consecutive pulses, as well as the other laser parameters (energy, beam homogeneity, fluence),
one could choose an appropriate regime to eliminate excessive photo-thermal and
photomechanical effects and obtain the desired surface structure and a controlled porosity.
Confocal microscopy images of modified zones were obtained in order to examine the
topography at the zones of interaction.
Acknowledgments
This work was supported by the Bulgarian National Science Fund (NSF) under project DMU
03/15/2011, and a Bulgaria/Austria bilateral project DNTS Austria/01/1/2013-2015.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
92
PB–15
COMPARISON OF DIFFERENT SUBSTRATES FOR LASER-INDUCED ELECTRON
TRANSFER DESORPTION/IONIZATION OF METAL COMPLEXES
A.A. Grechnikov1, V.B. Georgieva2, N.Y. Donkov3, A.S. Borodkov1, A.V. Pento4, Tc.A.
Yordanov2
1
Vernadsky Institute of Geochemistry and Analytical Chemistry of RAS, 19 Kosygin str.,
119991 Moscow, Russia,
2
Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72
Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
3
Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd.,
1784 Sofia, Bulgaria
4
“Energomashtekhnika” Ltd., prospect Vernadskogo, 123, b. 2, 119571 Moscow, Russia
Laser-induced electron transfer desorption/ionization (LETDI) is a novel variant of the laser
desorption/ionization technique. In LETDI, the analytes are preliminarily deposited on a
surface of a solid state substrate − an ion emitter. The emitter surface is subjected to a pulsed
laser radiation. This produces ions of the analytes, which are then analyzed by a mass
spectrometer. The ionization mechanism is based on electron transfer from the excited
adsorbed analyte molecule to the semiconductor material. The physical and chemical properties
of the substrate are known to play a critical role in the LETDI process. However, no sufficient
data is available to enable one to specify the properties that would make a substrate a good ion
emitter.
In this report, we compare the analytical performance of different substrates, including metal
materials, graphite, amorphous silicon (α-Si) and titanium dioxide (TiO2) films for laserinduced electron transfer desorption/ionization of several metal coordination complexes with
common organic reagents. All results were obtained by a laboratory-built LETDI-mass
spectrometer based on a time-of-flight reflectron (0.9 m) with orthogonal ion injection via a
gas-filled radio-frequency quadrupole. A diode-pumped Nd:YAG-laser with 355-nm
wavelength (third harmonic), 0,37-ns pulse duration and 500-Hz repetition rate was used for
desorption-ionization.
To investigate the mechanism of LETDI, we studied experimentally and theoretically the
dependence of the ion yield and the surface temperature on the fluence of the incident
radiation. The temperature was estimated using a numerical solution of a one-dimensional heat
conduction problem with a heat source distributed in time and space. It was found that at the
same temperature, the ion yield from different substrates varies in the range of three orders of
magnitude. The direct comparison of all studied substrates revealed that LETDI from TiO2
films and α-Si is a better choice for producing molecular ions of metal coordination complexes.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
93
PB–16
CORROSION PROPERTIES OF ZIRCONIUM-BASED CERAMIC COATINGS FOR
MICRO-BEARING AND BIOMEDICAL APPLICATIONS
J. Walkowicz1, V. Zavaleyev1, E. Dobruchowska1, D. Murzynski1, A. Zykova2, V. Safonov2 ,
S.Yakovin3, N. Donkov4
1
Institute of Technology and Education, Koszalin University of Technology, Koszalin, Poland
National Science Center „Kharkov Institute of Physics and Technology“, Kharkov, Ukraine
3
Department of Physical Technologies, Kharkov National University, Kharkov, Ukraine
4
Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko
Chaussee blvd., 1784 Sofia, Bulgaria
2
Excessive metal wear debris, which causes osteolysis and, consequently, a loosening of the
prosthesis, has caused the resurgence of the use of metal bearings in total and module joint arthroplasty. Modification of metal materials by means of ceramic coating deposition is an effective way of alternative bearing surfaces formation. The ZrN and ZrO2 ceramics and nanocomposite oxynitride coatings are widely used as protective coatings against wear, diffusion and
corrosion. The corrosion and wear resistance properties of modern coatings play a key role in
the future efficient applications for micro-bearings and for biomedical needs.
The aim of the present study was to study the effect of compositional, structural and morphological properties of ZrN, ZrO2 and oxynitride ZrON films on the corrosion characteristics of
the ceramic coatings produced. Stainless steel (AISI 316) discs with a diameter of 32 mm and a
thickness of 3 mm were used as substrates. The process of ZrO2, ZrN and oxynitride ZrON
coatings deposition by magnetron sputtering was performed in a high-vacuum pumping system
with a base pressure of about 10-3 Pa. The magnetron discharge power was 4 − 5 kW. An ICP
source for oxygen activation with RF power of up to 1 kW was applied. The main parameters
of deposition process were the following: Ar pressure Par = 2.3×10-1 Pa, oxygen mass flow rate
q = 35 sccm, nitrogen mass flow rate q = 27 sccm, magnetron voltage Um = 500 − 520 V,
magnetron current Im = 7.0 − 7.6 А, total pressure P = 2.8 − 3.0×10-1 Pa, coating deposition
rate 6 − 8 μm/hour. An ion source was used to clean the samples surface before deposition.
The coatings thickness was measured by Calotest. The adhesion properties, hardness and elastic modulus were evaluated by standard methods with the use of the Revetest (CSM Instrumets) and the Rockwell test with a diamond type C Rockwell indenter. To determine the micro-hardness, a Fischerscope® HM2000 tester was applied. The surface roughness parameters
were measured by a Hommel Werke T8000profilometer.
The surface morphology and topography were observed by optical microscopy and a JSM 5500
LV electron scanning microscope. The chemical composition of the coatings was analyzed by
energy dispersive X-ray (EDX) spectroscopy (Oxford Link ISIS 300). For potential metric studies, all samples were washed in ethanol in an ultrasonic bath before the measurements. The
active area of the sample was 0.287 cm2. All samples were kept in contact with the electrolyte
(isotonic NaCl (0.9%), 50 ml) for one hour before the measurements. The potential was in the
range 0.7 – 0.8 V for the reference sample and 0.5 – 1.0 V for all samples with deposited coatings, the sweep rate was 1 mV/s and the reading density, 3 mV. The temperature during the
measurements was kept at 25 ± 1 °C. The values of the corrosion potential (Ecor) and the corrosion current density (Icor) weree estimated using the method of the Tafel slopes extrapolation.
The results demonstrate an improvement of the corrosion characteristics of metal surfaces
coated by ceramic coatings. The corrosion resistance parameters increased in the cases of oxy-
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
94
nitride and oxide coatings. The development of new low-cost and innovative bearing surfaces
with enhanced corrosion characteristics is very challenging forfuture micro-bearing, joints replacement and other biomedical applications.
The study was supported within the 7th European Community Framework Program, ImBeingFP7-.PEOPLE-2013-IRSES-612593
PB–17
SURFACE MODIFICATION OF TANTALUM PENTOXIDE COATINGS
DEPOSITED BY MAGNETRON SPUTTERING AND FURTHER CORRELATION
WITH CELL ADHESION AND PROLIFERATION IN IN VITRO TESTS
N. Donkov1, A. Zykova2 , V. Safonov2, A. Goltsev3, T. Dubrava3, I. Rossokha3,., S.Yakovin4,
D. Kolesnikov5, I. Goncharov5
1
Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko
Chaussee blvd., Sofia, Bulgaria
2
National Science Center “Kharkov Institute of Physics and Technology“, Kharkov, Ukraine
3
Institute for Problems of Cryobiology and Cryomedicine NASU, Kharkov, Ukraine
4
Department of Physical Technologies, Kharkov National University, Kharkov, Ukraine .
5
Belgorod State National Research University, Belgorod, Russia
The clinical application of cell therapy methods requires the improvement of the traditional
tissue engineering approaches. Tantalum and tantalum-based compounds are promising for
biomedical applications due to their good dielectric properties. The aim of the present work
was to study the effect of argon-ion and electron-beam surface treatment on the structure and
surface properties of tantalum pentoxide (Ta2O5) coatings deposited by reactive magnetron
sputtering and, further, the correlation between the surface characteristics and the cell adhesion
and proliferation.
Ta2O5 coatings were deposited on Petri dishes glass substrates in a high-vacuum pumping system with a base pressure of about 10-2 Pa by ion source-assisted magnetron sputtering. Oxygen
for the reactive deposition was delivered through an ICP plasma source at q = 60 sccm; the
magnetron voltage was Um = 700 V, with magnetron current of about Im = 5,7 А.
For other substrates, the deposition process was carried out with simultaneous bombardment of
the growing film by argon ions using an ion source. The ion source parameters were as
follows: magnetic field current 1.5 A, ion acceleration voltage 2.5 kV, ion source current
30 mA. A primary electron beam was created by a UL-119 type electron gun. The energy of
the reflected electrons was 20 kV, the current density on the sample surface, 14 mA /cm2, the
irradiation time, 1500 s.
The structural parameters of the as-deposited and post-treated coatings were investigated by
means of transmission electron microscopy using JEOL JEM 2100. The surface topography
and roughness parameters of the oxide ceramic coatings were evaluated by scanning electron
microscopy (QUANTA 600 FEG) and atomic force microscopy. X-ray diffraction coating
profiles were observed by means of a DRON-3 diffraction device. X-ray photoelectron
spectroscopy was carried out using an ESCALAB MkII (VG Scientific) electron spectrometer
with a AlKalpha X-ray source (excitation energy hν = 1486.6 eV). The total surface free energy, polar and dispersion parts were estimated by applying the Wu and Owens-Wendt-RabelKaeble’ methods.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
95
Culturing of bone marrow (BM) cells was performed with a density of 0.5 − 1×104 cells/cm2.
After passage, the cells were removed by a trypsin-EDTA solution (Sigma-Aldrich, USA).The
structural and functional characteristics of the BM cells were evaluated. Visual control of the
cell cultures was carried out using a Primo Star light phase-contrast microscope (Zeiss, Germany) and an Axiovert 40C inverted microscope (Zeiss, Germany). The BM cells’ adhesive potential was also evaluated.
It was shown that the tantalum pentoxide coatings after electron beam irradiation can increase
cell adhesive and proliferative potential in comparison to as-deposited coatings. In contrast, the
argon ions bombardment during coating deposition process reduces the adhesive and
proliferative potential of BM cells.
The study was supported within the collaboration Program BAS-NASU and project No. 24-0415 NASU.
PB–18
INVESTIGATION OF THE MECHANICAL STABILITY OF ANODIC ALUMINUM
OXIDE WITH VACUUM DEPOSITED THIN METAL FILM
A. Bankova, V. Videkov, K. Raykov, B. Tzaneva, M. Mitov
Technical University of Sofia, 8, St. Kliment Ohridski blvd., 1000 Sofia, Bulgaria
E-mail: a_bankova@tu-sofia.bg
Nanostructured anodic aluminum oxide (AAO) is widely used in micro and nano electronics.
AAO is used in a variety of sensors and microelectromechanical systems (MEMS). In the last
few years, the use of AAO as a substrate has become more and more common. Some applications require that conductive tracks or conductive areas with a specific shape be formed on the
AAO substrate. In this work we investigated the mechanical stability of anodic aluminum
oxide with a thin metal film deposited on it in vacuum. Thin metal film meanders were deposited through a metal mask on free-standing membranes of AAO. The ends of the meanders
were wire-bonded to provide electrical contact. Using a series of mechanical bends, we investigated the stability ot the metal film on the AAO substrate and the stability of the system
"AAO - thin metal film". By measuring the resistivity of the metal film, we investigated the
maximum angle of deflection and the maximum elongation of the AAO substrate before the
metal tracks are broken. The results can be used as a reference for the design of MEMS devices
incorporating similar structures.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
96
PB–19
SURFACE PHOTOVOLTAGE AND PHOTOLUMINESCENCE STUDY
OF THICK Ga(In)AsN LAYERS GROWN BY LIQUID-PHASE EPITAXY
V. Donchev1, M. Milanova2, J. Lemieux3, N. Shtinkov3, I.G. Ivanov4
1
Faculty of Physics, St. Kliment Ohsridski University of Sofia, 5, J.Bourchier blvd., 1164
Sofia, Bulgaria
2
Central Laboratory of Applied Physics, 59 St. Petersburg blvd, 4000 Plovdiv, Bulgaria
3
Department of Physics, University of Ottawa, Ottawa, ON, K1N 6N5, Canada
4
, Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping,
Sweden
The addition of nitrogen in small concentrations is known to shift the absorption edge of III-V
materials to the longer wavelengths, which makes dilute III-V nitrides promising materials for
third-generation multi-junction solar cells. We present an experimental and theoretical study of
Ga(In)AsN layers with thickness around 1 μm, grown by liquid phase epitaxy (LPE) on n-type
GaAs substrates. The samples were studied by surface photovoltage (SPV) spectroscopy in the
metal-insulator-semiconductor geometry mode [1] and by photoluminescence spectroscopy.
Theoretical calculations of the absorption spectra were carried out using a full-band tightbinding approach in the sp3d 5s*sN parameterisation [2]. The SPV spectra measured at room
temperature are sensitive to the optical absorption spectrum of the structures and clearly show a
red shift of the absorption edge with respect to the absorption of the GaAs substrate. The shift
is of the order of 50 − 60 meV. The analysis of the SPV amplitude and phase spectra provides
information about the alignment of the energy bands across the structures. Photoluminescence
measurements performed at 2 K show a red shift of the emission energy of 50 − 60 meV with
respect to GaAs, in good agreement with the SPV results. Theoretical calculations of the
electronic structure and the spectral dependence of the dielectric constant were carried out for
different nitrogen concentrations and show a good agreement with the experimental data. The
results obtained contribute to a better understanding of the physical properties of dilute nitride
materials grown by LPE and their potential for optoelectronic applications.
[1] L. Kronik, Y. Shapira Surface photovoltage phenomena: theory, experiment, and
applications. Surf. Sci. Rep., 37, 1-206 (1999).
[2] N. Shtinkov, P. Desjardins, R.A. Masut, Empirical tight-binding model for the electronic
structure of dilute GaNAs alloys, Phys. Rev. B 67: 081202 (R)/1-4 (2003).
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
97
PB–20
INTERFACE CHARACTERIZATION OF NANOSCALED SiOx LAYERS GROWN
ON RF PLASMA HYDROGENATED SILICON
E. Halova1, N. Kojuharova1, S Alexandrova1, A Szekeres2
1
Department of Applied Physics, Technical University of Sofia, 1797 Sofia, Bulgaria
Institute of Solid State Physics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
3
Department of Solid State Physics and Microelectronics, St. Kliment Ohridski University of
Sofia, 1164 Sofia, Bulgaria
Email: nkojuharova@tu-sofia.bg
2
Control and characterization of the defects at the interfaces in single or multilayered structures
is an important issue in modern semiconductor devices. The incorporation of hydrogen into a
semiconductor structure is known for its beneficial effect, such as stabilization of the device’s
characteristics mainly through gettering of impurity defects. In silicon technology, hydrogenation has been widely used in the past decade in lower concentrations for improving the defect
and leakage characteristics and in higher concentrations for future nanoelectronic applications,
such as exfoliation of silicon in smart cut processes, increasing the carrier life-time in solar
cells, etc.
The aim of the present work is characterization of the interface between rf plasma hydrogenated (100) p-Si wafers and the overgrown SiOx by thermal oxidation at 850oC. The interface
traps density spectra are supposed to depend on the amount of incorporated hydrogen. For this
purpose, plasma hydrogenation of the Si wafers was conducted either without heating the Si
substrates or heating them up to 300 oC and the interface traps density spectra were examined
in detail. The thickness of the SiOx layers varied depending on the hydrogenation level, but
was in the nanoscale range below 10 nm, as determined from the ellipsometric measurements.
In order to examine the interface traps, MOS capacitors were built incorporating the Si/SiOx
structures. As a characterization tool, multiple frequency C-V and G-V measurement techniques were used. A generalized C-V curve was generated by applying the three-frequency
method to the C-V and G-V characteristics taken at a variety of frequencies ranging from 50 Hz
to 300 kHz. In this curve, the in-series resistance and the leakage through the oxide layer was
accounted for. The energy spectra of the interface traps were extracted by comparing the experimental and the generalized C-V curves. Ellipsometric data and the capacitance in strong
accumulation of the C-V curves were used to calculate the thickness and the dielectric constants of the oxide layers.
The analysis of the electrical characteristics showed that the C-V and G-V curves of the MOS
structures with SiOx layer grown on Si treated in plasma exhibit a small oxide charge and low
leakage currents typical for a high-quality dielectric layer. The interface density spectra
showed the presence of localized interface traps energetically distributed in the Si bandgap.
The positions and the height of the trap levels in the Si bandgap depended on substrate hydrogenation temperature and were related to particular structural defects at the interface and in a
thin region inside the oxide. The conclusions are well correlated with the results on the oxide
mechanical stress level, oxide composition and Si-O ring structure and the composition of the
interfacial region from our previous detailed multi-angle spectral ellipsometric and IR studies.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
98
PB–21
STUDY OF THE NEW CSAR62 POSITIVE TONE ELECTRON BEAM RESIST
AT 40 kEV ELECTRON ENERGY
R. Andok1, K. Vutova2, A. Bencurova1, E.Koleva2, P. Nemec1, P. Hrkut1,
I. Kostic1, G. Mladenov2
1
Institute of Informatics, Slovak Academy of Sciences,
Dubravska 9, 84507 Bratislava, Slovakia
2
Institute of Electronics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
One of the few “top-down” methods for fabrication of nanodevices is the e-beam lithography,
which allows flexible patterning of devices with a nanoscale resolution down to less than
10 nm. A thinner, more resistant to etching, and more sensitive e-beam resists are required for
the better control, linearity, and uniformity of the critical dimensions of structures for fabrication of nanodevices. Within the last decade, researchers have made a significant effort to improve the resolution limits of the nanoscale e-beam lithography. The resist material properties
are an important factor governing the resolution. This work deals with the investigation and
simulation of the characteristics of the AR-P 6200 (CSAR 62) positive beam resist (Allresist).
The investigations are performed for a 400-nm layer of the CSAR 62 positive e-beam resist
onto a Si substrate for the case of an electron energy of 40 keV. The contrast and sensitivity
characteristics are obtained experimentally for various development conditions.
The energy deposition function (EDF) is an important parameter in e-beam lithography. The
EDF (characterizing resist modification after e-beam exposure), which can reflect the absorbed
energy distribution in both lateral and depth direction (3-dimensional), is required for calculation of accurate resist profiles. The scattering trajectories of electrons in CSAR 62 and in the Si
substrate are obtained by Monte Carlo (MC) simulation to calculate discrete data for EDF. The
proximity effect parameters (βf, βb, ηE) for
a point e-beam source are calculated
through the MC technique. Discrete data
for EDF at the resist-substrate interface (at
the depth of 400 nm) are compared with an
analytical approximation using a sum of
two Gaussians (Figure 1). The variation of
the proximity effect parameters’ values
along the resist depth is evaluated in order
to calculate 3D-EDF, taking into account
the development process simulation.
Figure 1 Comparison between the discrete data obtained (▪) and its analytical fit (solid line).
The CSAR 62 is characterized by a similar resolution; however, it exhibits a higher sensitivity
and a significantly improved plasma etch resistance in comparison to the widely used highresolution positive e-beam resist PMMA (poly-methyl-methacrylate).
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
99
PB–22
ENHANCED PHOTOANISOTROPIC RESPONSE IN AZOPOLYMER
DOPED WITH ELONGATED GOETHITE NANOPARTICLES
L. Nedelchev1, D. Nazarova1, N. Berberova1, G. Mateev1, V. Salgueiriño2, D.
Schmool3
1
Institute of Optical Materials and Technology, Bulgarian Academy of Sciences, 1113 Sofia,
Bulgaria
2
Department of Applied Physics, University of Vigo, 36310, Vigo, Spain
3
Laboratory PROMES CNRS, University of Perpignan, 66100 Perpignan, France
*Corresponding author: natali.berberova@gmail.com
We present a study of the photoinduced birefringence in nanocomposite films of an
azopolymer (PAZO) doped with nanoparticles (NP) of the magnetic material Goethite (αFeOOH). The NP have an elongated shape with a size 15×150 nm, i.e. a ratio of 1:10. Samples
with different concentrations of the NP in the azopolymer were prepared by varying the concentration from 0 % (non-doped azopolymer film) to 15 %. An unusual dependence of the
birefringence on the concentration was observed in the present experiments – two peaks of
enhancement at 1 % and at 10 % concentration. Our previous studies with ZnO and SiO2 NP
have indicated only one peak of increase at low concentrations – 0.5 % and 2 % respectively.
This effect could be related with the elongated shape of the nanoparticles and the presence of
two characteristic NP sizes – 15 and 150 nm. Moreover, the birefringence increase for the
samples with 10 % NP concentration compared with the non-doped samples is rather
significant – nearly 70%.
PB–23
PHOTOINDUCED VARIATION OF THE STOKES PARAMETERS OF LIGHT
PASSING THROUGH THIN FILMS OF AZOPOLYMER-BASED HYBRID
ORGANIC/INORGANIC MATERIALS
N. Berberova, D. Nazarova, L. Nedelchev, B. Blagoeva, D. Kostadinova, V.
Marinova, E. Stoykova
Institute of Optical Materials and Technology, Bulgarian Academy of Sciences, 1113 Sofia,
Bulgaria
Corresponding author: natali.berberova@gmail.com
Hybrid materials synthesized by combining polymers and inorganic nanoparticles (NP) received considerable attention recently due to their advantageous electrical, optical, or mechanical properties. Here we present a polarimetric study of thin films prepared from photoanisotropic
hybrid
materials:
azopolymer
(poly[1-[4-(3-carboxy-4hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt]) doped with different
concentrations of ZnO NP with sizes below 50 nm. To obtain the complete information about
the polarization response of these thin films, we determined the kinetics of the Stokes parameters of light passing through the films on illumination with linearly polarized light within the
100
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
absorbance band of the material, namely, 473 nm. Using the Stokes parameters, the birefringence values are calculated as a function of time and compared for films with different NP
concentrations.
PB–24
INVESTIGATION OF THERMAL PROCESSES IN ELECTRON-BEAM SURFACE
MODIFICATION BY MEANS OF A SCANNING ELECTRON BEAM
M. Ormanova1, V. Angelov2, P. Petrov1,
1
Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee blvd.,
1784 Sofia, Bulgaria
2
Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
In this work we present an investigation of the thermal processes during surface modification
of steels performed by means of a scanning electron beam. A model was developed for description of the thermal processes taking place in the electron-beam material processing realized by
a scanning electron beam. The model is based on solving the heat-transfer equation by means
of Green functions. The thermal field was calculated, as well as the size the zone of structural
changes in instrumental steel samples.
In order to evaluate the applicability of the thermal model, we carried out experiments on samples of instrumental steel W 320 (0.31 % C, 0.30 % Si, 0.35 % Mn, 2.9 % Cr, 2.8 % Mo, 0.5
% V). The size of the samples was 20×20×4 mm. The experiments were conducted by means
of a Leybold Heraeus EWS 300/15-60 electron-beam installation using a scanning electron
beam for sample processing. The technological parameters of the processing were: accelerating
voltage U = 55 kV, scanning beam current I = 40 mA, sample motion speed V = 4 cm/s, focusing current If = 484 mA, frequency of electron-beam deflection f = 1 kHz, scanning beam diameter d = 0.1 mm.
The comparison of the experimentally observed zones of thermal treatment with the theoretically calculated ones and the corresponding structural changes showed a very good agreement.
Keywords: electron beam processing, thermal model, Green functions
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
101
PB–25
ELECTRON-BEAM INDUCED SURFACE ALLOYING OF TITANIUM WITH
ALUMINIUM
S. Valkov, D. Dechev, N. Ivanov, P. Petrov
Institute of Electronics, Bulgarian Academy of Sciences
72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
A summary is presented of the investigations on the mechanism of an alloyed layer formation
during electron-beam surface alloying of titanium with Al. Surface alloys were produced by a
two-step process: first, Al films were deposited on commercially pure Ti substrates by DC
magnetron sputtering in Ar atmosphere, which was followed by treatment by a scanning electron beam. Before the aluminium film deposition, the Ti substrates were cleaned by sputtering
for ten minutes. The electron-beam treatment was carried out using a Leybold Heraeus installation (EWS 300/15-60).
The crystallographic structure of the samples prepared was characterized by X-ray diffraction
with Cu Kα characteristic radiation (1,54 Å). The experiments were performed on a fully automated Seiferd&Co diffractometer with a scintillation detector and a flat graphite monochromator on the diffracted beam. The samples were further characterized by Raman spectroscopy
and scanning electron microscopy (SEM).
The dependence was analyzed of the phase composition and the crystallographic parameters of
the specimens on the different technological parameters of the electron beam treatment. It was
been found that the presence of several possible intermetallic Ti-Al phases (Ti3Al, AlTi,
Al3Ti), responsible for important mechanical properties of the samples, strongly depend on the
technological parameters of the electron-beam treatment. Other important crystallographic parameters, such as lattice parameters, crystal texture, etc, were also evaluated; it was found that
they also strongly depend on the technological parameters of the electron-beam treatment.
PB–26
STRUCTURAL MODIFICATION OF Ga+-ION IMPLANTED TA-C FILMS
M. Berova1, M. Sandulov1, T. Tsvetkova1, D. Karashanova2 and L. Bischoff3
1
Institute of Solid State Physics, Bulgarian Academy of Sciences
72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
2
Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences
Acad. G. Bontchev str., bl. 109, 1113 Sofia, Bulgaria
3
Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum DresdenRossendorf, P.O.B. 51 01 19, 01314 Dresden, Germany
Thin film samples (d ~ 40 nm) of tetrahedral amorphous carbon (ta-C), deposited by filtered
cathodic vacuum arc (FCVA), were implanted with Ga+ at an ion energy E = 20 keV and ion
doses D = 3×1014 ÷ 3×1015 cm-2. The Ga+-ion-beam induced structural modification of the implanted material results in a considerable change of its optical properties consisting in a significant shift of the optical absorption edge to the lower photon energies, which is accompanied by
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
102
a considerable increase of the absorption coefficient (photo-darkening effect) in the photon energy range measured (0.5 ÷ 3.0 eV). These effects could be attributed to the Ga+-ion-beam induced structural modification, in the form of introduction of additional defects and increased
graphitization, as well as the formation of Ga atoms clustering, as revealed by transmission
electron microscopy (TEM) and scanning electron microscopy (SEM) measurements. These
underlying structural changes define the optical photo-darkening effect observed, which could
be applied to for information archiving, in the area of high-density optical data storage while
using focused Ga+ ion beams.
PB–27
VIBRATIONAL SPECTROSCOPY OF Ga+-ION-IMPLANTED TA-C FILMS
M. Berova1, M. Sandulov1, T. Tsvetkova1 and L. Bischoff2
1
Institute of Solid State Physics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
2
Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum DresdenRossendorf, P.O.B. 51 01 19, 01314 Dresden, Germany
In the present work, low-energy Ga+-ion-beam implantation was used for modification of the
structural and optical properties of tetrahedral amorphous carbon (ta-C) thin films. Thin film
samples (d ~ 40 nm) of ta-C, deposited by filtered cathodic vacuum arc (FCVA), were implanted with Ga+ at an ion energy E = 20 keV and ion doses D = 3×1014 ÷ 3×1015 cm-2. The
Ga+-ion-beam-induced structural modification of the implanted material results in a considerable change of its optical properties consisting in a significant shift of the optical absorption
edge to the lower photon energies as obtained from optical transmission measurements. This
shift is accompanied by a considerable increase of the absorption coefficient (photo-darkening
effect) in the measured photon energy range (0.5÷3.0 eV). These effects could be attributed
both to additional defect introduction and increased graphitization, as well as to accompanying
formation of bonds between the implanted ions and the host atoms of the target, as confirmed
by infra-red (IR) and Raman measurements. The optical contrast thus obtained (between implanted and unimplanted film material) could applied to information archiving, in the area of
high-density optical data storage, while using focused Ga+ ion beams.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
103
PB–28
CHEMICAL BATH DEPOSITION OF THIN TIN SULPHIDE FILMS
D. Dimitrov1, L. Komsalova1, D. Lilova2, M. Sendova-Vassileva1, G. Popkirov1, P. Vitanov1,
I. Gadjov2, M. Ganchev1
1
Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences
72 Tsarigradsko Chaussee blvd, 1784 Sofia, Bulgaria
2
University of Chemical Technology and Metallurgy
8 Climent Ohridsky blvd, 1756 Sofia, Bulgaria
Tin sulphide is an attractive binary semiconductor with favorable electro-physical properties
and abundant elements and can be deposited as thin films by simple preparation methods. In
order to understand the possibilities for its application in photovoltaic devices, a chemical bath
deposition approach to form SnS thin layers on soda lime glass substrates at different
temperatures and solution compositions was developed.
Differential scanning calorimetry was used to reveal the thermo-chemical behavior of the asdeposited SnS and the possibility for suitable annealing treatment. The DSC analysis showed a
well-defined temperature interval of heat absorbing (endothermic) reaction of 150 oC – 166 oC
where the (re)crystallisation of the as-formed SnS takes place.
X–ray diffractometry of SnS deposited at different temperatures showed an improvement in the
crystal structure. A totally amorphous material, as obtained at 60 oC, underwent a gradual
transtion at 70 oC and 90 oC to well-defined patterns of orthorhombic Herzenbergite syngony.
The XRD pattern of already DSC-processed SnS (from 50 oC up to 220 oC at a rate of
10 oC/min) showed the full spectrum of the related powder diffraction file for Herzenbergite.
Optical investigations of as-deposited and annealed SnS thin films showed a region of
absorption near 400 – 600 nm and were used to estimate the band gap for allowed transitions.
The optical band gaps for samples annealed at different temperatures from 100 oC up to 260 oC
were calculated. Raman spectra of the same films showed typical vibrations for the SnS phase
and another one at the higher temperatures related to the SnS2 phase, which could explain the
variation of the estimated band gap observed as the temperature was raised.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
104
PB–29
MeV ELECTRON IRRADIATION OF Si-SiO2 STRUCTURES WITH MAGNETRON
SPUTTERED OXIDE
S. Kaschievaa, Ch. Angelovb, S.N. Dmitrievc
a
Institute of Solid State Physics, Bulgarian Academy of Sciences
72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
b
Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences
72 Tsarigradsko Chaussee blvd.,1784 Sofia, Bulgaria
c
Joint Institute for Nuclear Research, Flerov Laboratory of Nuclear Reactions
Dubna, Moscow Region 141980, The Russian Federation
MeV electrons influence on the characteristics of a Si-SiO2 structure with magnetron
sputtered oxide was studied by ellipsometry and the thermally stimulated current technique.
The MOS structures used in this study were fabricated on <100> oriented p-Si substrates of
12.75-17,25 Ω cm resistivity. Magnetron sputtered oxides with different thicknesses of 20 nm
and 100 nm were deposited. Both groups of samples were irradiated by 23 MeV electrons. The
oxide thicknesses and the TSC characteristics of the MOS sample were measured before and
after irradiation by doses of 4.80×1015 and 4.8×1016 cm-2. The activation energy and the concentration of the defects generated by MeV electrons were also evaluated. It was shown that
the trap concentration increases as the electron irradiation dose was increased. The main peak
in the TSC characteristics gives information about the main radiation defects at the Si-SiO2 interface of the structures. These defects can be related to the vacancy-boron complexes which
are associated with the main impurities in the p-Si substrate.
This study supports our results reported earlier for MeV electron irradiated Si-SiO2 structures
with thermally grown oxide. However, the effects observed are more pronounced for the
magnetron sputtered oxide. A possible reason is the more effective increase of the oxygen concentration at the Si-SiO2 interface after MeV electron irradiation. This is connected also with
the higher concentration of defects generated in the magnetron sputtered oxide during its deposition.
PB–30
WIRE BONDING ON VACUUM DEPOSITED THIN METAL FILM OVER
NANOSTRUCTURED ALUMINUM OXIDE
K. Raykov, V. Videkov, A. Bankova
Technical University of Sofia, 8, St. Kliment Ohridski blvd., 1000 Sofia, Bulgaria
In recent years, nanostructured anode aluminum oxide (AAO) has been widely used in various
areas of human activity. In micro- and nano-electronics AAO is used in a variety of sensors
and microelectromechanical systems (MEMS). Its unique properties and its low cost make it an
attractive material for use in the electronics industry. With the development of MEMS devices,
a large number of solutions have been proposed involving a semiconductor structure on a beam
or membrane of AAO. It is also possible to form conductive tracks on the AAO surface, where
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
105
the problem arises of implementing electrical contacts between the semiconductor structure on
the AAO substrate and the tracks. Wire bonding is a well known process for realizing electrical
contacts, also because the size of the wire is highly suitable for this purpose. This work
investigates various types of wire bonds on metal layers of different thickness deposited in
vacuum on substrates of AAO. A study of the wire bonds characteristics was conducted, as
well as of the behavior of nanostructured AAO during and after the wire bonding process.
PB–31
GOLD DISTRIBUTION ON LATENT FINGERMARKS DEVELOPED BY VACUUM
METAL DEPOSITION
K.T. Popov1,2, V.G. Sears3 and B.J. Jones1,2,4
1
School of Materials, University of Manchester, United Kingdom
2
University of Huddersfield, United Kingdom
3
CAST, Home Office, United Kingdom
4
Science, Abertay University, Dundee, United Kingdom
Fingermark development is one of the key methods for forensic identification. A latent fingerprint is formed from the material left on a surface after being touched and is often invisible. In
order to be visualized, the latent fingerprint needs to be developed, by one of a range of techniques. One such development method is vacuum metal deposition (VMD), a two-step process
of sequential evaporation and deposition of gold followed by zinc in vacuum. This method is
particularly useful for old and environmentally exposed fingermarks. In normal development,
the exposed gold particles between the fingermark ridges and around the fingermark serve as
nucleation sites for zinc deposition, while on the ridges no zinc is deposited as the gold particles submerge into the fingermark material. In some instances, however, problematic developments occur: reverse development (zinc only on the ridges), empty prints (no zinc on both
the ridges and space between them but surrounding the fingermark) and overdevelopment (zinc
is deposited everywhere). This work studies the gold distribution on fingermarks and the substrates on which they are deposited.
Scanning electron microscopy reveals that between the ridges the gold appears as a uniform
nanoparticle distribution, while on the fingermark ridge there are random shaped granules or no
gold particles resolvable. In addition, the presence of an irregular area surrounding the fingermark ridges is revealed. Here the gold particles appear with a reduced contrast. The presence
and size of this area is related to the fingermark donor and substrate and is linked to the presence of a thin layer of deposited material surrounding the fingermark ridge, revealed by atomic
force microscopy. These results allow us to propose a model for the gold distribution on the
fingermarks and how this affects the resultant fingerprint development.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
106
PB–32
THICKNESS INFLUENCE ON THE MORPHOLOGY AND THE SENSING ABILITY
OF THERMALLY DEPOSITED TELLURIUM FILMS
T. Hristova-Vasileva1, I. Bineva1, A. Dinescu2, D. Nesheva1, D. Arsova1, B. Pejova3
1
Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee
blvd., 1784 Sofia, Bulgaria
2
National Institute for R&D in Microtechnologies – IMT Bucharest, 126 Erou Iancu Nicolae
str., 077190 Bucharest, Romania
3
Faculty of Natural Sciences and Mathematics, Sts. Cyril and Methodius University, P.O. Box
162, 1001 Skopje, Macedonia
Tellurium films with nominal thicknesses of 30, 90 and 300 nm were prepared by thermal evaporation in vacuum at a low deposition rate of 0.3 nm/s. The morphology evolution with the
increase of the film thickness was observed by scanning electron microscopy and atomic force
microscopy (Fig. 1). Nanorods with a width of about 40 nm is observed on the thinnest films
surface whose root-mean-square roughness (Sq) is ~7 nm – Fig. 1a. On the 90-nm thick films,
the formations grow in priority to the z- direction to nanoblades with the same width and length
of about 100 nm (Fig. 1b). The further increase of the thickness leads to an increase of the 2D
nanoobjects width and length and formation of stacked nanosheet structure (Fig. 1c). The Sq
increases with the thickness.
Preliminary investigations of the sensing ability of the as-deposited tellurium films with
different thicknesses towards water (H2O), ethanol (C2H5OH), acetone (C3H5OH), and
ammonia (NH3) vapors were performed by measuring the vapor induced changes in the film
dark current. The films show appreciable response only to ammonia vapors; their sensitivity is
almost equal for the 30 and 90 nm thick films, and decreases significantly for the thickness of
300 nm.
a)
b)
c)
Fig. 1. SEM microphotographs (magnification of 100 000 times) of Te films with nominal
thickness of a) 30, b) 90 and c) 300 nm.
Acknowledgements: The authors acknowledge the support of the Bulgarian Academy of
Sciences (contracts ISSP-VK 03/14 and the bilateral projects with the Romanian Academy of
Sciences and with the Macedonian Academy of Sciences and Arts), as well as of the National
Science Fund (contract DMU 0391/2011).
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
PC–1
SLOW HIGHLY CHARGED ION
TRANSMISSION THROUGH CARBON
NANOMEMBRANES AND GRAPHENE
R.A. Wilhelm, E. Gruber, R. Heller,
S. Facsko, F. Aumayr
POSTER SESSION C:
THIN FILMS DEPOSITION. COATINGS FOR
ADVANCED APPLICATIONS
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
109
PC–1
SLOW HIGHLY-CHARGED IONS TRANSMISSION THROUGH CARBON
NANOMEMBRANES AND GRAPHENE
R.A. Wilhelm1, E. Gruber2, R. Heller1, S. Facsko1, F. Aumayr2
1
Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials
Research, Dresden, Germany, EU
2
Institute of Applied Physics, Technical University of Vienns, Vienna, Austria, EU
Slow highly-charged ions (HCI) showed in many studies their efficiency in forming surface
nanostructures, especially on insulating surfaces [1]. Here we report on the transmission of
HCI through carbon foils with a thickness of only 1 nm and less (graphene). At these
thicknesses, the neutralization of the slow HCI is not completed in the solid and, thus, effects
of pre-charge-equilibrium stopping of slow ions can be addressed experimentally.
We found that transmitted highly-charged Xe ions with charge states between Q = 10 and
Q = 30 show a bimodal charge state distribution, i.e. one part of the ions is transmitted in low
exit charge states combined with a large charge exchange enhanced kinetic stopping. The other
part of the ions, however, shows only a very small charge exchange with almost no kinetic
energy loss [2]. Both charge exchange regimes are attributed to different impact parameter
regimes, i.e. close collisions lead to extremely large charge exchanges and distant collisions are
connected with weak ion-target interactions. Thus, our measurements reveal that sub-surface
neutralization of HCI proceeds in a step-like fashion, i.e. either the ion approaches a target
atom closely and correspondingly neutralizes almost completely (∆Q > 20 for Q = 30), or it
passes through the material almost unchanged (∆Q < 5) until it hits a target atom at some larger
depth. A bimodal charge state distribution could therefore not be observed for larger target
thicknesses [3], except for the inverse case of a swift heavy ion charging up during
transmission through a silicon single crystal under random vs. channeling direction [4]. Gas
phase experiments on the other hand cannot lead to slow HCI neutralization in one single
scattering event using light target atoms (e.g. carbon), because here only atomically bound
electrons can contribute to the neutralization process (6 electrons in case of carbon) rather than
de-localized electrons in a solid target.
[1] Aumayr, F., Facsko, S., et al., Single ion induced surface nanostructures: a comparison
between slow highly charged and swift heavy ions. J. Phys. Condens. Matter 23, 393001
(2011)
[2] Wilhelm, R. A., Gruber, E. et al., Charge Exchange and Energy Loss of Slow Highly
Charged Ions in 1 nm Thick Carbon Nanomembranes. Phys. Rev. Lett. 112, 153201 (2014)
[3] Schenkel, T., Briere, M et al., Charge State Dependent Energy Loss of Slow Heavy Ions in
Solids. Phys. Rev. Lett. 79, 2030–2033 (1997)
[3] Dauvergne, D., Scheidenberger, A., et al. Charge states and energy loss of 300-MeV/u U73+
ions channeled in a silicon crystal. Phys. Rev. A 59, 2813–2826 (1999).
110
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
PC–2
PLASMA-ASSISTED CVD PRODUCTION OF ISOTOPES OF GROUP IV AND VI
ELEMENTS IN THE FORM OF THIN FILMS, NANOPARTICLES AND BULK
MATERIAL
P.G. Sennikov1, R.A. Kornev1, S.V. Golubev2.
1
G.G. Devyatykh Institute of Chemistry of High-Purity Substances, Russian Academy of
Sciences, Nizhny Novgorod, The Russian Federation, pgsen@rambler.ru
2
Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, The Russian
Federation
In the chemical vapor deposition (CVD) process, the starting molecules of gasses and vapors
are “chemically activated” due to the resistive heating before deposition. In plasma-enhanced
chemical vapor deposition (PECVD), chemical activation is achieved by supplying electrical
power to a gas at a reduced pressure, typically between 10 mTorr and 10 Torr. At these pressures, the application of a sufficiently high voltage creates a visible glow-discharge plasma
(called low-temperature non-isothermal plasma). The electrical power is coupled into the gas
through the mediation of the plasma electrons. The energetic electrons in the plasma ionize the
gas to a minor extent. On the contrary, a much larger fraction of the gas is chemically activated
by the electrons. The increased chemical activity of the gas results primarily from dissociation
of the molecules into radicals. These species are unsaturated and therefore capable of chemical
reactions at high rates resulting in formation of solid and gaseous products. Depending on the
experimental conditions, the solid deposits possess different chemical and phase structure. The
PECVD method is widely used for laboratory and industrial production of different chemical
substances and elements.
The advantage of this approach is clearly demonstrated in the case of precursors with highenergy chemical bonds. Inorganic fluorides of different elements belong to this group of substances. Besides, fluorine is monoisotopic, hich is why volatile fluorides are used in centrifugal
processes of isotopic separation (enrichment). The classical illustration of this approach is the
isotopic enrichment of uranium hexafluoride.
This report summarizes the main results of recent investigations carried out at the Institute of
Chemistry of High-Purity Substances and the Institute of Applied Physics of the Russian
Academy of Sciences in Nizhny Novgorod in creating the physico-chemical background of
plasma-chemical production of chemically and isotopically pure of groups IV and VI elements
(silicon, germanium, sulfur, molybdenum) from their enriched fluorides.
The main features are discussed of the plasma-chemical reactions of hydrogen reduction of the
isotopically enriched tetrafluorides SiF4 и GeF4 in HF, UHF and ECR discharges resulting in
deposition of silicon and germanium in the form of thin films, nanoparticles and small polycrystals. It is shown that the laboratory approach suggested could be scaled up for production
of tens of kilograms of the germanium-76 isotope in the form of large polycrystals for the international GERDA and MAYORANA projects dealing with the study of neutrino-less doublebeta decay. The results of the experiments on reduction of 98MoF6 in hydrogen plasma resulting
in production of 98Мо nanoparticles are discussed. The nanoparticles obtained should be converted into radioactive 99Мо isotope and further to metastable 99mТс that is widely used for diagnostics of various diseases. The particularities of 32SF6 reduction in plasma are discussed as
well.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
111
PC–3
MASS-SPECTROMETRY INVESTIGATION OF PLASMA FOR PARYLENE C
DEPOSITION
N. Lukat, E. von Wahl, H. Kersten
Institute for Experimental and Applied Physics, University of Kiel
This work details the results of mass spectrometry in an asymmetric rf-discharge used to
deposit parylene C. Parylene is the trade name of a variety of chemical vapor deposited
poly(para-xylylene) polymers with a wide range of applications. It is used as a hard coating in
medicine because of its biocompatibility and stability, in the car industry to protect metallic
surfaces from corrosion, and in the aviation industry to protect electrical circuits.
The common conventional method to deposit parylene C is chemical vapour deposition (CVD)
with dichloro[2,2]paracyclophane as a precursor. [2,2]paracyclophane is a hydrocarbon which
consists of two benzene rings and an aliphatic chain that connects these rings. The prefix
dichloro means that one hydrogen atom in each benzene ring has been replaced by a chlorine
atom.
The CVD of parylene C is a three-step process in which the precursor is sublimated at a
temperature of about 150 °C. Afterwards, the precursor is pyrolysed at a temperature of
approximately 680 °C to a 1,4-chinondimethan radical. This radical is highly reactive and on
surfaces polymerizes to parylene C. To achieve the necessary process conditions, the steps
must be spatially separated. Neither the energy consumption nor the complexity of the
pyrolysis is a disadvantage during the CVD. However, near the pyrolysis temperature, the arylchlorine bond in the precursor readily breaks. For this reason, along with the desired monomer
1,4-chinodimethan, chlorine radicals and [2,2]paracyclophane are also created which
polymerize on surfaces to another parylene, namely, parylene N. The above makes clear the
importance of chemistry in the deposition processes.
In this work, plasma is used for dissociation instead of high temperatures. The feedstock for
this plasma is a composition of argon and a small amount of dichloro[2,2]paracyclophane. Due
to the use of plasma, the process is called Plasma Enhanced CVD (PECVD . The advantage of
this method is that the energy for dissociation is provided by the impact of hot electrons, while
the neutral atoms and radicals are nearly at room temperature. The aim of the mass
spectrometric investigation is to understand the chemical reactions running in the plasma and
how they are affected by changes in the discharge parameters.
112
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
PC–4
INFLUENCE OF THE PREPARATION METHOD ON THE OPTICAL PROPERTIES
OF GeS1.2 – AgI FILMS
D. Nicheva1,2, V. Ilcheva2, T.Petkova2, I.N. Mihailescu3, G. Popescu-Pelin3, G. Socol3, C. Ristoscu3, P. Petkov1
1
Department of Physics, University of Chemical Technology and Metallurgy
8 St. Kliment Ohridski blvd., 1756 Sofia, Bulgaria
2
Institute of Electrochemistry and Energy Systems, Bulgarian Academy of Sciences
Acad. G. Bonchev bl. 10, 1113 Sofia, Bulgaria
3
Laser-Surface-Plasma Interactions Laboratory, National Institute for Lasers, Plasma and Radiations Physics, PO Box MG-54, Magurele, RO-77125, Romania
Thin films from the chalcohalide (GeS1,2)1-x(AgI)x system (x = 5, 10 ,15, 20 mol. %) were deposited by pulsed laser deposition (PLD) and vacuum thermal evaporation (VTE) from the corresponding bulk materials. Structural, morphological and surface topography studies were performed in order to elucidate the effect of the process parameters and preparation method on the
films properties. The amorphous character of the films was confirmed by X-ray diffraction
analysis. The morphology and topography were investigated by scanning electron microscopy
and atomic force microscopy. The transmission spectra of the films were measured within the
wavelength range (400 – 2500) nm and the optical band gap was calculated as a function of the
films composition and the preparation method.
It was found that the values of the optical band gap (Eg) of the films are strongly dependant on
the addition of silver iodine to the glassy matrix and the method of preparation. It was assumed
that the difference in the Eg values of VTE- and PLD- fabricated films is due to the peculiarities of the preparation technique providing differences in the films structure.
PC–5
STUDY OF THE MORPHOLOGY OF GE QUANTUM DOTS GROWN BY LIQUID
PHASE EPITAXY
I.I. Maronchuk1, D.D. Sankovitch1, H. Nichev2, D. Dimova-Malinovska2
1
Laboratory of Applied Physics and Nanotechnologies for Energy Applications, Sevastopol
National University of Nuclear Energy and Industry, 7 Kurtchatova str.
299033 Sevastopol, The Russian Federation
Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences,
72 Tsarigradskao Chaussee blvd., 1784 Sofia, Bulgaria
Recently, the study of nano-heterojunctions based on c-Si and Ge quantum dots (QDs) have
attracted the interest of many research teams due to their potential for photovoltaic and
photothermal application. The theoretical calculation demonstrated that the maximal efficiency
of the c-Si/Ge QDs solar cells is 53 %, which is twice as high as the efficiency of commercial
c-Si solar cells (22 %).
This work reports the results of a study of the process of growing QDs of a narrow-band
semiconductor (Ge) in the matrix of a wide-band material (Si) by liquid-phase epitaxy applying
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
113
pulsed cooling of the substrate. The influence was studied of the different technological
conditions on the size of the Ge QDs and the density of their distribution. The morphology of
the structures was studied by AFM using a CMM-200 type microscope.
The results demonstrate that after applying 1 and 3 cooling pulses, the Ge QDs formed are very
small with a height of 5 and 10 nm and a width of 20 and 60 nm, respectively, with a 20 %
deviation, while their shape cannot be determined accurately. Increasing the number of the
pulses to 5 and 10 results in increasing their size, the height being 70 and 150 nm, the width,
190 − 250 nm, respectively, with a 35 % deviation. The Ge QDs have a shape close to the
pyramidal one and the density of their distribution on the Si surface is 1 − 2 × 1010 cm-2.
However, the samples grown by applying seven pulses have a totally different morphology
compared to the samples grown by applying five and ten pulses. Their shape is not welldefined; they look like drops with a width of 150 nm; however their height decreases and is
15 nm. The QDs growth is explained by the Stranski-Krastanoff mechanism and by the
authors’ theoretical prediction published previously [1].
[1] I. E. Maronchuk, T. F. Kulyutina, I. I. Maronchuk, Method of growth epitaxial nano heterojunction structures with quantum dots array. Patent of Ukraine, UA № 94699, cl. С 30В 19/00,
С 30В 29/00, Н 01L 21/20, 10.06.2011, bulletin. №5.
Acknowledgements: The work has been supported by the Bulgarian National Scientific Fund,
grant DNTS/Ukraine 01/0005.
PC–6
ARENECARBOXIMIDE DERIVATIVES AS DYE-SENSITIZERS APPLIED TO THIN
FILM SOLAR CELLS
H. Nichev2, N. Georgiev1, M. Petrov2, K. Lovchinov2, D. Dimova-Malinovska2,
V. Bojinov1
1
Department of Organic Synthesis and Fuels, University of Chemical Technology and Metallurgy, 8 St. Kliment Ohridski blvd., 1756 Sofia, Bulgaria
2
Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of
Sciences, 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
Expanding the applications of PV systems requires the development of new, more efficient and
less expensive technologies. The dye-sensitized solar cells (DSSCs) are cheap alternatives to
silicon solar cells for efficient conversion of solar energy into electrical energy, which is why
they have attracted the attention of the scientific community. For the last ten years, increasing
efforts have been devoted to the development of organic sensitizers (organic chromophores) for
solar cells with high photo-conversion efficiencies. Representatives of these materials are the
arenecarboximide (ACI) derivatives, owing their unique chemical, thermal and especially photochemical stability.
In this work we report on the preparation of three types of ACI layers by dipping in the solution of glasss substrate covered by SnO2, ITO and ZnO thin films for solar cells formation. The
SnO2, ITO and ZnO thin films are used as backside electrodes, and the Ag grid, as front electrodes. The current-voltage characteristics of the cells are measured and discussed.
Keywords: solar cells, arenecarboximide derivatives.
114
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
PC–7
DEPOSITION OF CARBON NANOSTRUCTURES ON METAL SUBSTRATES AT
ATMOSPHERIC PRESSURE
Zh. Dimitrov, M. Nikovski, Zh. Kiss'ovski
Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 James Bourchier blvd., Sofia,
Bulgaria
Plasma-enhanced chemical vapor deposition is the main method of carbon nanostructures
synthesis; however, the conditions ensuring fast growth have to be achieved by varying the
plasma parameters in the experimental set-up. One of the challenges remains synthesizing such
carbon nanostructures by microwave plasma at atmospheric pressure. The microwave
discharge produces dense plasma and provides the appearance of reactive species with high
concentration needed to ensure the deposition process. Processing the samples at atmospheric
pressure allows the deposition period to be shortened and also simplifies the set-up. In this
study, we investigated the relation between the substrate temperature and the type of the carbon
nanostructures deposited. The process of deposition itself is carried out by an additionally
negative DC potential applied to the substrate. The temperature is varied in a wide range using
the microwave plasma heating as well as an additional heater [1]. The distance between the
substrate and the plasma flame is also varied in order to establish the conditions for efficient
deposition process. The deposition process is carried out in specific argon/hydrogen/methane
gas mixtures [2]. Optical measurements of the plasma flame spectrum above the microwave
discharge tube are conducted to obtain the gas temperature, plasma density and to analyze the
existence of reactive species in order to establish their role in the deposition process. The
structures deposited on the metal samples are investigated by SEM and the relation of the
morphology with the gas-discharge conditions is discussed.
[1] Kiss’ovski Zh, Djermanova N, Mitev D and Vachkov V. J. of Physics: Conf. Series 514,
012007 (2014)
[2] Y. H. Wu,T. Yu, Z. X. Shen “Two-dimensional carbon nanostructures: Fundamental
properties,synthesis, characterization, and potential applications” Journal of Applied Physics
108, 071301 2010
Acknowledgments: This work was supported by Project BG051 PO 001-3.3.06-0057, Operational Program Human Resources Development 2007—2013
PC–8
VACUUM DEPOSITED ORGANIC SOLAR CELL STRUCTURES
G. Georgieva1, D. Dimov2, G. Dobrikov3, M. Vala1, M. Weiter1, and I. Zhivkov1,2
1
Faculty of Chemistry, Center for Materials Research, Brno University of Technology, Purkynova 118, 612 00 Brno, The Czech Republic
2
Acad. J. Malinovski Institute for Optical Materials and Technologies, Bulgarian Academy of
Sciences, Acad. G. Bonchev str., bl. 109, 1113 Sofia, Bulgaria
3
Faculty of Electronic Engineering and Technologies, Department of Microelectronics, Technical University of Sofia, 8 St. Kliment Ochridski blvd., 1756 Sofia, Bulgaria
E-mail: zhivkov@fch.vutbr.cz
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
115
Zinc phthalocyanine (ZnPc) and diphenyl-diketo-pyrrolopyrroles (DPP) thin films were
deposited in vacuum on ITO covered substrates. Aluminum top electrodes were also prepared
by vacuum evaporation on the organic film (OF). As a result, solar cell structures of the
ITO|OF|Al type were produced by an all-dry process that avoids the usage of a solvent.
The device parameters were estimated by measuring the current-voltage characteristics in dark
and under white light illumination. The light was produced by a solar simulator according to
the AM 1.5 standard.
The spectral dependence of the photoconductivity was measured and the spectral region for
optimal photoelectrical energy conversion was determined. On some of the structures, additional sub- and over-layers were also deposited in vacuum to optimize the device performance.
A post-deposition treatment was applied to selected samples to improve the device performance.
It was found that the photovoltaic properties of the samples depend on the conditions for
deposition of the top Al electrodes. Increasing the substrate temperature during the electrode
deposition worsens the photoelectrical properties. The optimal conditions for electrode
deposition were established, which allows reproducible samples to be prepared. Under these
conditions, a clear diode dark current characteristics with a diode rectification ratio of 1×105
were obtained. Under light exposure of samples with ZhPc active films, an open-circuit voltage
of 0.7 V was observed, while the photocurrent increased by more than five orders of
magnitude. It was also found that the post-deposition treatment improves the device parameters, especially influencing the solar cell efficiency.
Acknowledgements
This work was supported by the Czech Science Foundation under project No. 15-05095S; the
research infrastructure was supported by project MŠMT No. LO1211.
PC–9
MAGNETRON SPUTTERING OF Fe-OXIDE MAGNETIC FILMS ON DIELECTRIC
AND SUPERCONDUCTING SUBSTRATES
T. Nurgaliev1, E. Mateev1, L. Slavov1, 3, B. Blagoev2, 3, G. Gajda3, I. Nedkov1
1
Institute of Electronics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria
2
Institute of Solid State Physics, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria
3
International Laboratory of High Magnetic Fields and Low Temperatures,
95 Gajowicka Str., 53-421 Wroclaw, Poland
Thin films of iron (Fe) and iron oxides (FexOy) possess unique magnetic and electric properties
and are considered suitable candidates for application in sensors, microwave and magnetooptic
devices. Magnetic oxides and the ferromagnet/superconductor structures have also been the
subject of numerous experimental and computational investigations in view of applications in a
very promising area of electronics − spintronics. Magnetron sputtering is one of the main
methods used for growing high-quality films of complex oxides. The most challenging
problem in growing monophase iron oxide thin films of α-Fe2O3, γ-Fe2O3 and Fe3O4 is the
narrow area of transition between phases in the phase diagram of FexOy, so that a precise
116
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
control of the deposition conditions is necessary during the technological process.
We report some preliminary results of RF magnetron sputtering of a Fe target in Ar or Ar/O2
atmosphere with the purpose of preparing magnetic FexOy films. The deposition was carried
out on Si, Al2O3 substrates at several substrate temperatures. The magnetic properties, the
electrical conductivity and the transparency of the films strongly depended on the deposition
conditions, especially, on the temperature of the substrate. A FexOy layer was deposited on a
surface of a SrTiO3 substrate covered by a high-temperature superconducting YBa2Cu3O7-x film
as well. The deposition at lower substrate temperatures did not destroy the superconductivity
and the sample exhibited superconducting properties at 77 K.
PC–10
INFLUENCE OF THE PULSED LASER DEPOSITION PARAMETERS ON THE
PROPERTIES OF EPITAXIAL GST FILMS ON Si(111)
Isom Hilmi, Erik Thelander, Philipp Schumacher, Jürgen W. Gerlach, Bernd Rauschenbach
Leibniz-Institut für Oberflächenmodifizierung e.V., Leipzig 04318, Germany
E-mail: isomi.hilmi@iom-leipzig.de
Thin films of Ge2Sb2Te5 (GST) are considered promising candidates for application as phasechange materials with respect to switching speed and stability1. Currently, improved switching
characteristics have been shown by tailoring a superlattice-like structure of GeTe and Sb2Te3
layers2, which then gave rise to investigations of higher-order structures of GST materials. One
of them has been realized by epitaxial growth of Ge-Sb-Te films in highly-ordered atomic arrangement by means of MBE3. However, with this method, there is a severe limitation in terms
of the deposition rate which is typically around 0.3 − 0.5 nm per minute4. In this point, pulsed
laser deposition (PLD) has been used successfully for deposition of GST5 as it offers significantly higher GST deposition rates.
In this work, epitaxial GST thin films were grown on single crystal Si(111) substrates by
means of PLD. The influence of the PLD parameters, namely, laser pulse repetition rate and
fluence, on the crystalline quality of the films was investigated by means of X-ray diffractionbased measurements. The film topography was investigated using AFM in tapping mode. The
results show that the PLD parameters have a significant impact on the crystal quality of the
grown GST.
1.
2.
3.
4.
5.
A. V. Kolobov, et. al., Nature Material, Vol. 3, October, 2004.
R. E. Simpson et. al., Nat. Nano. 6, 501, 2011.
F. Katmis et. al., Cryst. Growth, Des. 11, 4606, 2011.
R. Shayduk, et. al., Journal of Crystal Growth, 311, 2215–2219, 2009.
H. Lu, et al., Adv. Funct. Mater. 23, 3621–3627, 2013.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
117
PC–11
MORPHOLOGICAL AND OPTICAL INVESTIGATION OF SOL-GEL ZNO FILMS
T. Ivanova1, A. Harizanova1, A. Petrova2
1
Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of
Sciences, 72 Tzarigradsko Chaussee blvd., Sofia, Bulgaria
2
Space Research and Technology Institute, Bulgarian Academy of Sciences, Acad G. Bonchev
Str., bl. 1, 1113 Sofia, Bulgaria
Zinc oxide has been widely studied as one of the binary II–VI semiconductor compounds with
a hexagonal wurtzite structure possessing an optical band gap of 3,37 eV and a large exciton
energy. Other interesting properties of ZnO include its optical, acoustical and electrical
properties, high photosensitivity, high optical transparency in the visible region and stability
which can be useful in the fields of electronics, optoelectronics and sensors. Some potential
applications are as piezoelectric transducers, optical waveguides, acousto-optic media, surface
acoustic wave devices, conductive gas sensors, transparent conductive electrodes, solar cell
windows, and varistors.
This works presents an easy-to-implement sol-gel process for deposition of ZnO films, which
is proved to be a very flexible approach to modification of the structural, vibrational and
optical properties by simply changing the solvent used in the sol solution. The influence of
different thermal treatments is studied. The films microstructure is explored using a NanoScan
family scanning nano-hardness measuring device in constant frequency regime, which is based
on the atomic force microscopy principle. The surface study revealed that the RMS surface
roughness for 985,64×985,64 nm ZnO films increases as the annealing temperature is
increased, but the film surface is still uniform and smooth. The results were confirmed by XRD
analysis which demonstrated that the crystallite sizes grow from 25 to 36 nm with the thermal
treatment. The ZnO films possess high transmittance in the visible spectral range, while the
optical band gaps in ZnO films vary from 3.25 eV to 3.52 eV. The optical and morphological
properties of ZnO films on Si and quartz substrates thus revealed are very good. The sol-gel
approach proposed for deposition of nanostructured ZnO films is promising for applications to
optoelectronic devices and solar cells.
118
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
PC–12
SYNTHESIS AND PROPERTIES OF ZnO:Al THIN FILMS PREPARED BY SOL-GEL
METHOD
T. Ivanova1, A. Harizanova1, T. Koutzarova2, B. Vertruyen3
1
Central Laboratory of Solar Energy and New Energy Sources,Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee blvd., Sofia, Bulgaria
2
Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd,
Sofia, Bulgaria
3
LCIS/SUPRATECS, Institute of Chemistry B6, University of Liege, Sart-Tilman, B-4000
Liege, Belgium
ZnO has been the object of intensive scientific research due to its specific properties, such as a
wide band gap (3.37 eV at room temperature) with a large exciton binding energy (60 meV), a
high chemical stability, a low dielectric constant, a large electrochemical coupling coefficient, a
high thermal conductivity, and binding, antibacterial and UV protection properties. Doping
ZnO by different metals leads to modifying its structural, electronic and optical properties.
Aluminium-doped ZnO coatings exhibit a high transparency and a low resistivity. The sol-gel
technology offers the possibility to produce high-quality homogeneous thin films on large areas
with excellent control of the stoichiometry and compositional modification (mixing on a
molecular level) via a cost-effective process using inexpensive equipment.
This work presents a sol-gel technological process for deposition of thin films of ZnO and
ZnO:Al. The effect on their properties of annealing treatments (500, 600, 700 and 800 oC) was
studied. The structural evolution with the temperature was investigated by using X-ray
diffraction (XRD). Fourier transform infrared (FTIR) and UV-VIS spectrophotometry were
applied for characterization of the vibrational and optical properties. The ZnO and ZnO:Al
films possessed a polycrystalline structure. The pure ZnO film crystallized in a wurtzite phase
with a weak reflection associated to cubic ZnO2. The ZnO:Al spectrum revealed only the XRD
lines of wurtzite ZnO without any other crystalline phases. The Al component influenced the
crystallization of the films and the crystallite size significantly diminished in comparison with
pure ZnO films. The average crystallite size of ZnO was 32.3 nm, and that for ZnO:Al was
20.0 nm. The Al additive affected the shapes and intensity of the IR absorption features without
clear indication of bands, which can be associated with Al-O bonds. The FTIR analysis led us
to a conclusion in agreement with the XRD study, namely, that the only crystal phase detected
was wurtzite ZnO. The films studied were highly transparent in the visible spectral range as the
transparency was improved by the aluminium doping. The optical band gap values and haze
parameter were also determined. The haze parameter serves as an indicator of diffuse light
scattering by the thin films.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
119
PC–13
INFLUENCE OF THE SURFACE PRETREATMENT OF ALUMINUM ON THE
PROCESSES OF FORMATION OF CERIUM OXIDES PROTECTIVE FILMS
R. Andreeva1, E. Stoyanova1, А. Tsanev2, D. Stoychev1
1
Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, Acad.
G. Bonchev str., bl. 11, Sofia 1113, Bulgaria
2
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G.
Bonchev str., bl. 11, Sofia 1113, Bulgaria
There exists a special interest in the investigating the conversion treatment of aluminum aimed
at promoting its corrosion stability, which is focused on electrolytes on the basis of salts of
metals belonging to the group of rare-earth elements. Their application is especially attractive,
as it enables a successful substitution of the presently applied highly efficient, but at the same
time toxic Cr6+-containing electrolytes. The present work presents a study on the influence of
the preliminary alkaline activation and acidic de-oxidation of the aluminum surface on the
processes of immersion formation of protective cerium oxides films on Al-1050. The results
obtained show that their deposition from simple electrolytes (containing only salts of Ce3+
ions) on the Al surface, treated only in an alkaline solution, occurs at a higher rate, which leads
to preparing thicker oxide films having a better protective ability. In the cases when the
formation of oxide films is realized in a complex electrolyte (containing salts of Ce3+ and Cu2+
ions), better results are obtained with respect to the morphology and protective action of
cerium oxides film on samples which have been consecutively activated in an alkaline solution
and deoxidized in an acidic solution.
Electrochemical investigations were carried out in a model corrosion medium (0.1 M NaCl); it
was shown that the cerium protective films deposited by immersion are of a cathodic nature in
regard to the aluminum support and inhibit the occurrence of the depolarizing corrosion
process – the reaction of oxygen reduction.
Key words: aluminum, pretreatment, cerium-containing conversion films, corrosion
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
120
PC–14
TRANSMISSION PHOTOCATHODES BASED ON STAINLESS STEEL MESH AND
QUARTZ GLASS COATED WITH N DOPED DLC THIN FILMS PREPARED BY
REACTIVE MAGNETRON SPUTTERING
N.I. Balalykin1, J. Huran2, M.A. Nozdrin1, A.A. Feshchenko1, A.P. Kobzev1, V. Sasinková3
1
Joint Institute for Nuclear Research, 6 Joliot-Curie str., 141980 Dubna,
Moscow Region, Russian Federation
2
Institute of Electrical Engineering, Slovak Academy of Sciences,
Dúbravská cesta 9, 84104 Bratislava, Slovakia
3
Institute of Chemistry, Slovak Academy of Sciences,
Dúbravská cesta 9, 84538 Bratislava, Slovakia
Laser-driven photoelectron sources are widely used in various scientific experiments for the
generation of high-quality electron beams. We investigated the influence of the properties of
N-doped diamond-like carbon (DLC) films on the quantum efficiency of transmission photocathodes. N-doped DLC thin films were deposited on a silicon substrate, a stainless steel mesh
and quartz glass (coated with a 5-nm thick Cr adhesion film) with an Al mesh made by the liftoff technique. The films were deposited by reactive magnetron sputtering using a carbon target
and an Ar+/N2 gas mixture. The film thickness for the silicon substrate and the stainless steel
mesh was about 150 nm, and for the quartz glass, about 25 nm. The elemental concentration in
the films was determined by RBS and ERD. Raman spectroscopy of the DLC films was used to
determine the D and G peaks intensity ratio (I(D)/I(G)). The G and D peaks were fitted by two
Gaussians, while the intensity was calculated as the peaks’ area. The quantum efficiency was
calculated from the measured laser energy and the measured cathode charge. The RBS and
ERD analyses indicated that the films contained carbon, hydrogen, nitrogen and a small
amount of oxygen. The photocathode was placed in a hollow cathode assembly of a DC gun
with a Pierce structure. To study the vectorial photoelectric effect, the quartz-type photocathode was irradiated by high-power laser pulses (3 − 4 pulses with a power of about 5 MW/cm2)
to create micron-sized perforation in the Cr and DLC films by laser ablation. The bunch charge
was measured by using a Faraday cup. The quantum efficiency (QE) calculated at a laser energy of 0,4 mJ inreased as the nitrogen concentration in the DLC films was increased, and dramatically rose up after the micron-sized perforation in the quartz-type photocathodes. The best
results achieved for the QE (%) was 0,84×10-3 for the quartz-type transmission photocathode.
The Prospectss for implementing N-doped DLC thin films on quartz glass transmission
photocathodes for application in the DC gun technology are discussed.
This research was executed in the framework of the Topical Plan for JINR Research and International Cooperation (Project 02-0-1067-2013/2017) and supported by the Slovak Research
and Development Agency under contract APVV-0443-12
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
121
PC–15
TRANSFORMATION OF ELECTROMAGNETICALLY INDUCED TRANSPARENCY
INTO ABSORPTION IN THERMAL K OPTICAL CELL WITH SPIN-PRESERVING
COATING
S. Gozzini1, A. Lucchesini1, C. Marinelli1,2, L. Marmugi1,4, S. Gateva3, S. Tsvetkov3, S.
Cartaleva3
1
Istituto Nazionale di Ottica CNR – UOS Pisa, Via Moruzzi 1, 56124 Pisa, Italy
Department of Physical Sciences, Earth and Environment, University of Siena, via Roma 56,
53100 Siena, Italy
3
Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd.,
1784 Sofia, Bulgaria
4
Department of Physics and Astronomy, University College London, Gower str., London
WC1E 6BT, UK
Electromagnetically induced transparency (EIT) and electromagnetically induced absorption
(EIA) are coherent phenomena with quickly expanding applications. In a Hanle configuration,
the EIA contrast (about 1%) is much worse than the EIT one. To enhance the EIA contrast, the
use of a transition with angular momenta of the ground and excited states F = 1 was recently
proposed [1].
We report a new experimental approach where an order of magnitude enhancement of EIA resonance contrast is obtained (Fig.1b), comparable to that of the EIT (Fig1a). Here, the EIA signal results from the interaction of a weak probe beam with a ground state that has been driven
by the pump (counter-propagating) beam. Figure 1 shows double scan probe absorption spectra
with the laser frequency slowly detuned over the D1 line of 39K vapor, in a cell with PDMS antirelaxation coating. At the same time, a magnetic field orthogonal to the laser beams is tuned
at a higher rate across zero. Note that: (i) changing the pump beam polarization from linear to
circular reverses the resonance signal from EIT to EIA and (ii) here, in the experimental absorption profile not only the transition with F = 1 is involved, but also two other hyperfine
transitions of the D1 line of 39K.
a)
0,7
b)
0,4
0,2
0,1
0,5
0,4
0,3
0,2
0,1
pump on
pump off
0,0
-1,0
-0,5
0,0
Probe beam absorption
0,3
Probe beam absorption
0,6
pump on
pump off
0,0
0,5
Laser frequency detuning
1,0
-1,0
-0,5
0,0
0,5
1,0
Laser frequency detuning
Fig.1 EIT (a) and EIA (b) resonances observed by means of a double scan: of (i) laser frequency
over the absorption profile and (ii) magnetic field varying around zero value; (a) pump and probe
beams are of linear polarization; (b) the pump is almost circularly (1:1.4) and the probe is linearly
polarized. (a) Wpump = 2.92 mW, Wprobe = 0.98 mW; (b) Wpump = 2.91 mW, Wprobe = 0.57 mW.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
122
This work was supported by Marie Curie International Research Staff Exchange Scheme Fellowship within the 7th European Community Framework Program and by the Italian National
Research Council and the Bulgarian Academy of Sciences (Program CNR/BAS 2013-2015).
[1] D V Brazhnikov, A V Taichenachev, A M Tumaikin, V I Yudin, Laser Phys. Lett. 11
(2014) 125702.
PC–16
STRUCTURAL, OPTICAL AND VIBRATIONAL PROPERTIES OF
NANOSTRUCTURED ALUMINUM NITRIDE FILMS SYNTHESIZED BY MULTISTAGE PULSED LASER DEPOSITION
L. Duta1, G.E. Stan2, M. Anastasescu3, H. Stroescu3, M. Gartner3, Zs. Fogarassy4, N.
Mihailescu1, C. Luculescu1, S. Bakalova5, A. Szekeres*,5, I.N. Mihailescu1
1
Lasers Department, National Institute for Lasers, Plasma, and Radiation Physics, P.O. Box
MG-36, 77125 Magurele, Romania;
2
National Institute of Materials Physics, 105 bis Atomistilor Street, P.O. Box MG-7, 77125
Magurele, Romania
3
Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy of Sciences, 202 Splaiul
Independentei, 060021 Bucharest, Romania
4
Research Institute for Technical Physics and Materials Science, Hungarian Academy of
Sciences, Konkoly Thege Miklos u. 29-33, H-1121 Budapest, Hungary
5
Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee
blvd., 1784 Sofia, Bulgaria; *szekeres@issp.bas.bg
Aluminum nitride (AlN) films have great potential for various applications due to their
excellent electronic, optical and thermal properties, which can be tailored by varying the
deposition methods and the technological conditions. AlN films are finding applications in
high-power and high-frequency devices, high-power switches, blue and ultraviolet lightemitting devices and photo-detectors. The successful fabrication of devices based on AlN thin
films requires a better understanding of the optical and electronic properties as related to the
growth conditions. Our recent studies were focused on pulsed laser multi-stage AlN deposition
at different temperatures aiming to obtain nanostructured AlN films at considerably lower deposition temperatures.
This report is focused on spectroscopic ellipsometry (SE) studies of the AlN films. In order to
support the SE results obtained, SEM, GIXRD and TEM were also applied. The SE measurements were performed in a wide region covering the near UV-VIS (193 − 1000 nm) and IR
(350 − 5000 cm-1) light spectra. The nanostructured AlN films were synthesized by multi-stage
pulsed laser deposition, with the first stage of deposition carried out at 800 °C, which was previously established to be the optimum temperature for AlN crystallization. The second stage,
homoepitaxial deposition, was conducted at reduced temperatures (450 °C, 350 °C, RT) at a
low nitrogen pressure of 0.1 Pa.
The results from the ellipsometric data modeling showed that the refractive index values were
lower than those obtained for crystalline AlN, but higher than those for amorphous AlN. This
was in accordance with the GIXRD and TEM observations that both crystalline and amorphous
phases existed in the films. By increasing the substrate temperature from RT up to 800oC,
nanocrystallites appeared in the amorphous matrix (as proved by TEM imaging and GIXRD
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
123
analysis), with a tendency of enhancing the crystallization and crystallites’ augmentation. For
the AlN films deposited at 350oC and 450oC, the values for the optical constants were close,
pointing to similar film structures approaching stoichiometric AlN. For the RT deposition, the
TEM imaging showed an amorphous phase, but the corresponding refractive index values were
higher revealing an over-stoichiometric AlN structure with excess of Al, as confirmed by the
SEM measurements. The band gap energy of AlN increased as the substrate temperature or the
laser pulse repetition rate were increased, which we attributed to the increased formation of
nanocrystallites of larger sizes, as proved by GIXRD analysis.
PC–17
ELECTRICAL PROPERTIES OF p-TYPE In-N CO-DOPED ZnO THIN FILMS
DEPOSITED ON DIFFERENT SUBSTRATES
M. Duta1, J. Calderon-Moreno1, S. Preda1, P. Osiceanu1, S. Mihaiu1, M. Zaharescu1, M. Gartner1, S. Simeonov2, D. Spasov2, A. Szekeres2
1
Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy of Sciences
202 Splaiul Independentei, 060021 Bucharest, Romania
2
Institute of Solid State Physics, Bulgarian Academy of Sciences
72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
Zinc oxide is a well-known material for opto-electonic applications. Presently, two research
directions have been established: depositing n-type thin films with high conductivity on flexible supports for display applications, or obtaining p-type conduction for incorporation in homo- and hetero-junctions. The second aim can be achieved by co-doping the film with donoracceptor pairs such as In-N, Al-N, B-N, etc.
We have deposited In-N co-doped ZnO thin films on four different substrates (glass, alumina,
n- and p-Si) through a combined sol-gel and hydrothermal method, followed by annealing at
500 oC for one hour and have investigated the direct or indirect influence of the substrate on
their electrical properties. The co-doped nature of the films was confirmed using XPS analysis.
The morphology of the films (determined by SEM) showed interconnected, randomly oriented
nanorods with a length of a few hundred nanometers. Three of the substrates promoted homogenous, continuous films, whereas alumina promoted film growth at the Al2O3 grain boundaries, leading to non-homogenous films with a lower thickness. The films crystallized in a wurtzite structure with no evident preferred orientation as indicated by the XRD and the random
orientation of the nanorods. Hall Effect (HE) measurements showed high resistivity for the film
deposited on alumina, due to the small thickness and the non-homogeneity. The conduction
type of the films deposited on n-Si as determined from HE and I-V and C-V measurements differred, suggesting the presence of a nitrogen gradient or that the conducting substrate contributes charges to the film. The presence of donor-type defects in the films was observed with
injected carriers trapped at these sites.
124
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
PC–18
IMPACT OF THE ACTIVE LAYER NANOMORPHOLOGY ON THE EFFICIENCY
OF ORGANIC SOLAR CELLS BASED ON A SQUARAINE DYE AS A DONOR
D. Stoyanova1, S. Kitova1, J. Dikova1, M. Kandinska2, A.Vasilev2, I. Zhivkov1,3
A. Kovalenko3
1
Acad. J. Malinovski Institute for Optical Materials and Technologies, Bulgarian Academy of
Sciences, Acad. G. Bonchev str., bl. 109, 1113 Sofia, Bulgaria
2
Faculty of Chemistry and Pharmacy, St. Kliment Ohridski University of Sofia, 1 James Bourchier blvd., 1164 Sofia, Bulgaria
3
Materials Research Center, Faculty of Chemistry, Brno University of Technology, Purkyňova
118, 612 00 Brno, Czech Republic
E-mail: skitova@iomt.bas.bg
During the past two decades, the organic solar cells (OSCs) have drawn intensive interest due
to their light weight and potential of low-cost and simple roll-to-roll production on flexible
substrates. In the most successful implementation, a soluble n-type fullerene derivative, (6,6)phenyl C61 butyric acid methylester (PCBM) as an acceptor, is blended with the donor from
conjugated p-type polymers or small molecular weight organic semiconductors to form bulkheterojunction (BHJ) cells. Although high PCEs of 9 – 10 % have been achieved, the polymer
solar cells still suffer from some shortcomings, such as batch-to-batch variation, indefinite
molecular weight, polydispersity and impurity. In contrast, small-molecule materials
intrinsically do not have such drawbacks. Additionally, the band structure of these materials
could be tuned more easily, while they exhibit a higher charge carrier mobility. Even though
the highest PCE of 7.38 % has been obtained by solution-processed small- molecule OSCs, it is
still lower than that of polymer solar cells owing mainly to the difficulty of controlling the nanomorphology and phase separation in the active layers, where donor and acceptor components
self-assemble to form bicontinuous interpenetrating networks. The latter allows the excitons to
diffuse to the donor-acceptor interface and the charge carriers to move to the respective
electrodes after separation. Because the photoexcitation/recombination lengths are typically
around 10 nm in these disordered materials, the length scale for this self-assembly must be of
the order of 10 – 20 nm.
In a previous work, we studied the potentiality of our newly synthesized symmetrical n-hexyl
substituted squaraine dye, (labeled as Sq1) for use as an electron donating component in BHJ
organic solar cells. The results obtained were very encouraging, which gave us reason to continue the investigations. In the present work, the influence is studied of the active layer morphology on the efficiency of OSCs based on Sq1 dye as a donor and PCBM as an acceptor. For
this purpose, the impact of solvent annealing processing on the nanomorphology and phase separation in the Sq1/PCMB blended layers with different donor/acceptor ratios is followed by
means of TEM. Further, the optical properties are estimated of the as-deposited and the annealed active layers, as well as the efficiency of cells designed on their basis. Thus, the very
important relationship was revealed between the Sq1/PCBM blend morphology and the photovoltaic performance of the organic solar cells studied. On this basis, the possibilities for practical application of the results obtained are discussed.
Acknowledgements: This work was supported by the Czech Science Foundation under project
No. 15-05095S; the research infrastructure was supported by project MŠMT No. LO1211.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
125
PC–19
OPTIMIZATION OF THE SERIES RESISTANCE IN BULK HETEROJUNCTION
POLYMER SOLAR CELLS
M. Sendova-Vassileva1, G. Popkirov1, P. Vitanov1, G. Grancharov2, V. Gancheva2, H. Dikov1,
E. Lazarova1
1
Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of
Sciences, 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
2
Institute of Polymers, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
The series resistance of solar cells is an important parameter which has a decisive influence on
their efficiency. The apparent value of the series resistance, Rser, is the sum of contributions of
the resistances of the different conducting and semiconducting layers of the solar cell and their
respective junctions. Rser cannot be measured directly; thus, a great number of measurements
methods have been reported, among which fitting the current-voltage characteristics of the cell
to a predefined model seems to be the most commonly used.
In this contribution, we present an alternative method, derived from the impedance spectroscopy, that uses a relatively high-frequency perturbation voltage with a low amplitude applied under conditions simulating an open circuit. The method is applied to polymer solar cells (PSCs)
of the type ITO/hole transporting layer (HTL)/bulk heterojunction (BHJ)/back contact or inverted ones of the type ITO/ BHJ/ HTL/back contact. The BHJs deposited by spin coating are
either the classic P3HT:PCBM combination or the high open-circuit voltage PCDTBT:PCBM
one. The HTL is either spin-coated PEDOT:PSS or an inorganic oxide layer (MoO3, WO3) deposited by magnetron sputtering. The back contact is sputtered or evaporated silver or aluminium. The series resistance measured is compared to the one estimated from the current-voltage
characteristics and the observed differences are analyzed. The data obtained concerning the Rser
can serve as one of the control parameters in our attempt to improve the PSCs technology.
PC–20
OPTICAL AND ELECTRICAL PROPERTIES OF NANOLAMINATE DIELECTRIC
STRUCTURES
Ch. Dikov, P. Vitanov, T. Ivanova
Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences,
72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
The wide application of transparent and conductive oxide (TCO) films to optoelectronics and
photovoltaics has promoted the development of low-cost materials and technological
processes. Most of the TCO films are binary or ternary compounds containing one or two
metallic elements. The combination of conductivity and transparency is impossible to achieve
in intrinsic stoichiometric oxides. In order to achieve conductivity in such materials, they
should be doped with an appropriate element.
The aim of this study is a formation of a conductive area in a nanolaminate dielectric structure.
The underlying physical idea is the usage of an electronic conductivity in granular type
126
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
materials. The granules are metallic particles of sizes ranging usually from a few to hundreds
of nanometers embedded into an insulating matrix.
The nanolayer structure is formed using one or two different dielectrics. The electrical
conductivity is modified with planar located metal granules. A magnetron sputtering system
with three different targets was used for the deposition of the layers. The advantages of this
method are reproducibility of technological parameters, effective process control and a
selective formation of conductive areas into the dielectric structure.
Our studies reveal that the relation between the sheet resistance and the maximum transparency
in the visible spectral range depends on factors such as the dimension of the metal granules ad
the thickness of the dielectric layers. Another possibility for engineering the optical and
electrical properties of nanolaminate structures is to use different metals and dielectrics layers.
We present the results of studying the temperature behavior of resistors with nanolaminate
structures. Usually, the TCOs layers have a semiconductor behavior of the conductivity, as a
negative temperature coefficient of receptivity (TCR). The nanolaminate structure with metal
granulate demonstrates a metallic conductivity, as it reveals a positive TCR.
The technological procedure applied to the formation of the transparent conductive coatings
makes it possible to predict their optical and electrical properties.
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
127
POST DEADLINE CONTRIBUTION
PA–27
THEORETICAL STUDY OF SURFACE-WAVE-DISCHARGES IN VACUUM–
PLASMA AND DIELECTRIC–PLASMA CONFIGURATIONS
K. Ivanov, T. Bogdanov, E. Benova
St. Kliment Ohridski University of Sofia, Sofia, Bulgaria
Electromagnetic wave travelling along the dielectric-gas interface can produce plasma.
These gas discharges called surface-wave-discharges (SWDs) exist in various geometries: planar, spherical, cylindrical, coaxial, and around dielectric cylinder. The typical coaxial surfacewave-sustained discharge (CSWD) is produced outside the dielectric tube when a metal rod is
arranged at the tube axis. The CSWD is studied intensively both theoretically and experimentally since 1998. The experimental investigations show that in some conditions the plasma can
be produced outside the dielectric cylinder even when there is not any metal antenna at the dielectric axis [1].
In order to find out theoretically these conditions and the plasma characteristics we
have built one-dimensional fluid model for vacuum–plasma and dielectric–plasma configurations. The basic relations in our model are the local dispersion relation describing the wave
propagation and the wave energy balance equation, both obtained from Maxwell’s equations.
Analyzing the phase diagrams, the axial profile of dimensionless plasma density and the 3D
distribution of electric and magnetic field components, one can obtain information about the
ability of the electromagnetic wave to sustain plasma at given discharge conditions.
The purpose of this work is to investigate theoretically the behaviour of wave phase
diagrams and axial profiles at various discharge conditions and to find out the values of plasma
parameters at which plasma can be sustained in vacuum–plasma and dielectric–plasma configurations.
Reference:
1. Liang R., Nie Z., Liang B., Liang Y., Chang X., He L., Li Z. MICROWAVE DISCHARGES: Fundamental and Applications, Ed. M. Kando and M. Nagatsu, Japan: 2009, 95.
Acknowledgements:
This work has been supported by the Fund for Scientific Research at the University of Sofia
under Grant No 187/2015.
128
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
AUTHOR`S INDEX
A
Adamek J.
Aftanas М.
Alexandrov M.T.
Alexandrova S.
Alexiou G.
Alipieva E.
Amanatides E.
Anastasescu M.
Anda G.
Andreeva R.
Angelov Ch.
Angelov V.
Arsova D.
Asenova I.
Atanasov P. A.
Atanasova G. B.
Atanasova M.
Aumayr F.
Avdeev G.V.
Ayrapetov A.A.
29
71
88
97
52
78
52, 54
122
30
119
104
100
106
74
85, 88, 89, 90
86, 87
48
109
87
55
99
41
101, 102
30
50
29, 71
106
101, 102
61
53, 83, 85, 115
62
99
47, 127
71
113
41
26
92
57
61
C
B
Balabanova E.
Balalykin N.I.
Bakalova S.
Bankova A.
Barton D.
Begrambekov L.B.
Beletskii A.
Belmonte T.
van den Bekerom D.C.M.
Beňačka Š.
Benčurová A.
Bencze A.
Benova E.
Berberova N.
Berden G.
Berova M.
Berta M.
Biederman H.
Bilkova P.
Bineva I.
Bischoff L.
Blagoev A.
Blagoev B.
Blagoev K.
Blagoeva B.
Bogdanov T.
Bohm P.
Bojinov V.
Bongers W. A.
Bornoldt S.
Borodkov A.S.
Boyadjiev S.
Bozhinova I.
72, 73
120
122
66, 95, 104
73
55
68
32
41
84
98
30
47, 48, 127
Cahyna P.
de la Cal E.
Calderon-Moreno J.
Cartaleva S.
Chechkin V.
Chernogorova T. P.
Chirita V.
Chromik S.
Clyne T.W.
Costea S.
Cruz J.
29
67
123
121
68
64
36
83, 84, 85
32
69
83
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
130
D
Damyanova M.
Dankov P.
Daskalova A.
Dechev D.
Dejarnac R.
Dias F.
Dikov Ch.
Dikov H.
Dikova J.
Dikovska A. O.
Dimitrov D.
Dimitrov D. Z.
Dimitrov Zh.
Dimitrova M.
Dimov D.
Dimova-Malinovska D.
Dinescu A.
Dinescu G.
Dmitriev S. N.
Dobrikov G.
Dobruchowska E.
Dokládalová L.
Donchev V.
Donkov N.Y.
Dubrava T.
Dunai D.
Duta L.
Dzharov V.
G
72, 73
72
91
101
29, 69, 70, 71
69
125
125
124
87
103
53
114
29, 69, 70, 71
114
112, 113
106
34
104
114
93
51
96
92, 93, 94
94
30
122, 123
74
E
Ehiasarian A. P.
Engeln R.
Evsin A.E.
37
41
55
Gadjov I.
Gajda G.
Gál N.
Ganchev M.
Gancheva V.
Gartner M.
Gateva S.
Gaži Š.
Georgiev A.
Georgiev N.
Georgieva G.
Georgieva V.
Georgieva V.B.
Gerlach J. W.
Ghafoor N.
Ghanbaja J.
Gleeson M.A.
Goltsev A.
Golubev S. V.
Goncharov I.
Gordeev A.A.
Gozzinia S.
Grancharov G.
Graswinckel M.F.
Grechnikov A.
Grigor’eva L.
Grozeva M.
Gruber E.
Grunin A.V.
Guaitella O.
Guerra V.
Gunn J. P.
Gyergyek T.
103
115
84
103
125
122, 123
121
84
61
113
114
57
92
22, 85, 116
35
39
40
94
110
94
55
121
125
41
92
68
49, 62, 63
109
55
42
24
31
79
H
F
Facsko S.
Fedchenko Yu. I.
Fekete L.
Feshchenko A.A.
Fogarassy Zs.
Fukata N.
109
65
51
120
122
85
Hacek P.
Halova E.
Hanus J.
den Harder N.
Harizanova A.
Hasan E.
Havlicek J.
Heller R.
Henrion G.
Hilmi I.
29, 30
97
50
41
117, 118
70
29, 69
109
32
116
Seventeenth International Summer School VEIT
19 – 23 September 2011, Sunny Beach, Bulgaria
Hirsch D.
Hohm U.
Honova J.
Horáková P.
Horwat D.
Hovsepian P. Eh.
Hristova-Vasileva T.
Hrkut P.
Hron М.
Huran J.
Husinsky W.
85
73
51
51
39
37
106
98
29, 71
120
91
I
Ignatova V.
Ilcheva V.
Imrisek M.
Iordanova E.
Iordanova S.
Ivanov I.G.
Ivanov K.
Ivanov N.
Ivanov O.
Ivanova P.
Ivanova T.
43
112
29
49
61
96
127
101
62
70, 71
117, 118, 125
J
Jones B.J.
Junek P.
105
70, 71
K
Kalachev A.M.
Kalampounias A.
Kandinska M.
Karashanova D.B.
Karatodorov S.
Kardjiev M.
Kaschieva S.
Kasilov A.
Kersten H.
Khvedchyn I.
Kiss’ovski Zh.
Kitova S.
Kleyn A.W.
55
52
124
88, 90, 101
49, 62
74
104
68
26, 111
56
78, 114
124
40
131
Kobzev A.P.
Kolev S.
Koleva E.
Koleva L.
Koleva M. E.
Kolesnikov D.
Komm M.
Komsalova L.
Konečníková A.
Kornev R. A.
Kostadinova D.
Kostič I.
Koujuharova N.
Koutzarova T.
Kovacheva D.
Kovačič J.
Kovalenko A.
Kozulya M.
Kratochvílová L.
Krbec J.
Kubáč L.
Kudryavtsev A.
Kuzminova A.
Kylian O.
120
90
74, 75, 98
75
89
94
29
103
98
110
99
98
97
90, 118
90
79
51, 124
68
51
30
51
63
50
50
L
Lazarova E.
Leclercq J. B.
Lemieux J.
Levchuk I.P.
Lilova D.
López-Bruna D.
Lovchinov K.
Lozin A.
Lucchesinia A.
Luculescu C.
Lukat N.
Luňák S.
125
53
96
76, 77
103
67, 71
80, 113
68
121
122
111
51
M
Malcheva G.
Maletić D.
Malinov P.
Malović G.
Marinellia C.
Marinov S.
62, 63
33
72
33. 69
121
69
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
132
Marinova P.
Marinova V.
Markovic T.
Marmugi L.
Maronchuk I.I.
Martin J.
Maslov V.I.
Mataras D.
Mateev E.
Mateev G.
Matejicek J.
Mehandzhiev V. B.
Michailova D.
Mihailescu I. N.
Mihailescu N.
Mihailov V.
Mihaiu S.
Milanova M.
Minea T.
Mironov Y.
Mitov M.
Mladenov G.
Mozetič M.
Mücklich F.
Muhl S.
Murzynski D.
48
99
29
121
112
32
76, 77
52, 54
115
99
69
53
61
112, 122
122
49, 62
123
96
41
68
66, 95
74, 75, 98
21
39
83
93
N
Nakajima Y.
Nathala C.
Nazarova D.
Nedelchev L.
Nedkov I.
Nedyalkov N. N.
Nemec P.
Nesheva D.
Nichev H.
Nicheva D.
Nickolov R.
Nikolov A.S.
Nikov R.G.
Nikov Ru.
Nikovski M.
Nominé A.
Nominé A.V.
Nozdrin M.A.
Nurgaliev T.
89
91
99
99
115
85, 88, 89, 90
98
106
80, 112, 113
112
86
88, 90
88, 90
85, 89, 90
78, 114
32
32
120
83, 85, 115
O
Öncel S.
Onishchenko I.N.
Ormanova M.
Osiceanu P.
34
76, 77
100
123
P
Panek R.
Pashov A.
Pavlichenko R.
Pavlov E.L.
Pejova B.
Peneva P.
Pento A.V.
Peterka M.
Petkov P.
Petkova T.
Petrov I.
Petrov M.
Petrov P.
Petrova A.
Petrović Z. Lj.
Pierson J.F.
Pirovska A.
Pisarčík M.
Popescu-Pelin G.
Popkirov G.
Popov K.T.
Popov Tsv. K.
Pramatarov P.
Preda S.
Puac N.
29, 30, 69, 70,
71
61
68
88
106
90
92
29
112
112
23
80, 113
100, 101
117
33, 69
39
63
84
112
103, 125
105
66, 67, 69, 70,
71
63
123
33, 69
R
Rauschenbach B.
Raykov K.
Restrepo J.
Ristoscu C.
van Rooij G.J.
Rossokha I.
85, 116
66, 95, 104
83
112
41
94
Seventeenth International Summer School VEIT
19 – 23 September 2011, Sunny Beach, Bulgaria
S
Sabchevski S.
Sadovskiy Ya.A.
Safonov V.
Saifutdinov A.
Salgueiriño V.
Sandulov M.
Sankovitch D.D.
van de Sanden M.C.M.
Sasinková V.
Sauchyn V.
Schmool D.
Schneider V.
Schumacher Ph.
Sears V.G.
Selaković N.
Seidl J.
Sendova-Vassileva M.
Shelemin A.
Shigin P.A.
Shtinkov N.
Sennikov P. G.
Simeonov S.
Slaveeva S. I.
Slavov L.
Slikboer E.T.
Šmatko V.
Sobota A.
Socol G.
Soldera F.
Sojkova M.
Španková M.
Spasic K.
Spasov D.
Spassova I.
Spethmann A.
Stan G.E.
Stankova N.E.
Stefanova M.
Stöckel J.
Stoeva N.
Stoyanchov T. R.
Stoyanova D.
Stoyanova E.
Stoychev D.
Stoykova E.
72
55
93, 94
63
99
101, 102
112
40, 41
120
56
99
26
116
105
33
29
103, 125
50
55
96
110
123
64, 65
115
42
84
42
112
39
83, 84, 85
84, 85
69
123
86
26
122
85, 90
63
29, 69, 70
71
86
85
124
119
119
99
133
Škoro N.
Štrbík V.
Stroescu H.
Sveshtarov P. K.
Szekeres A.
Szilágyi I. M.
69
83, 84, 85
122
53
97, 122, 123
57
T
Takami A.
Tankova V.
Taskova E.
Tatarova E.
Temelkov K. A.
Terakawa M.
Thelander E.
Todorov D.
Todorov G.
Trottenberg T.
Troughton S.C.
Tsanev A.
Tsigaras G.
Tsvetkov S.
Tsvetkova T.
Tyutyundzhiev N.
Tzaneva B.
89
62, 63
78
78
64, 65
89
116
75
78
26
32
119
52
121
101, 102
80
95
U
Ürgen M.
34
V
Vala M.
Valcheva E.
Valkov S.
Vasilev A.
Vasileva E.
Veres G.
Vertruyen B.
Videkov V.
Vitanov P.
Voitsenya V.
Vondráček P.
Vrakatseli V.E.
Vutova K.
51, 114
74
101
124
70, 72
30
118
66, 95, 104
103, 125
68
29, 71
54
98
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria
134
W
v. Wahl E.
Walkowicz J.
Weinzettl V.
Weiter M.
Wilhelm R.A.
Wong Y.
111
93
29, 69
51, 114
109
39
Y
Yakovin S.
Yankov G.
Yegorov A.M.
Yordanov O.
Yordanov Tc.A.
Yordanova D.
Yuferov V.B.
93, 94
49
76
38
92
63
76
Z
Zaharescu M.
Zahria T.
Zakharov A.M.
Zamanov N.
Zapryanov St.
Zavaleyev V.
Zhelyazkov I.
Zhivkov I.
Zoethout E.
Zoletnik S.
Zykova A.
123
40
55
68
61
93
72
114, 124
41
30
93, 94
NINETEENTH INTERNATIONAL SUMMER SCHOOL
ON VACUUM, ELECTRON AND ION TECHNOLOGIES
21 – 25 September 2015, Sozopol, Bulgaria
NOTES
136
Nineteenth International Summer School VEIT
21 – 25 September 2015, Sozopol, Bulgaria