LUMINESCENCE SPECTROSCOPY
OF WIDE-GAP SOLIDS
Eduard Aleksanyan
PostDoc at the Institute of Physics, University of Tartu
F
I
Tartu Ülikool · FÜÜSIKA INSTITUUT
INSTITUTE OF PHYSICS · University of Tartu
29.08.2013, Yerevan
Education
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1990 – 1997 Secondary School #20, Yerevan
1997 – 2000 Anania Shirakaci Lycey, Yerevan
2000 – 2004 Yerevan State University, Department of Physics
Bachelor of Science
2004 – 2006 Yerevan State University, Department of Physics,
Master’s School
2006 – 2009 Yerevan Physics Institute, Department of Solid State
Physics, PhD student
2007 – 2008 Institute of Physics, University of Tartu, Department of
ionic crystals, Tartu, Estonia, PhD student
2009 – 2011 Yerevan Physics Institute, Department of Solid State
Physics, Researcher
2011 - 2014 Institute of Physics, University of Tartu, Department of
ionic crystals, Tartu, Estonia, PostDoc
OUTLINE
 Luminescence Spectroscopy
 Synchrotron Radiation
o
o
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SUPERLUMI
BW3
MAX-III
 Intrinsic (e-h pairs or excitons) and extrinsic
(impurity ions and defects) luminescence
 Scintillators, phosphors, LEDs
 Conclusion
Spectral ranges of electromagnetic radiation
Conduction band
-
Exciton
Energy
1. Radio and mirowave radiation:  > 1 mm
2. Inrfa-red (IR) radiation: 750 nm <  < 1 mm
a) Far_IR: 10 m <  < 1 mm
b) Mid-IR: 2.5 m <  < 10 m
c) Near-IR: 750 nm <  < 2500 nm (2.5 m)
3. Visible light: 400 nm <  < 750 nm
4. Ultraviolet (UV): 200 nm <  < 400 nm
5. Vacuum ultraviolet (VUV): 10 nm <  < 200 nm
6. X-rays: 0.01 nm <  < 10 nm
7. Gamma-rays:  < 0.01 nm
Excited
states
Eex
Eg
Impurity
ion
Ground
state
+
Valence band
Regions where most of electronic transitions take place
SPECTROSCOPY OF 4fn-1 - 5d CONFIGURATION
SPECTROSCOPY OF 4fn-1 - 5d CONFIGURATION
CONFIGURATION OF Er3+
ENERGY OF LOWEST 4f n-1 - 5d
LEVELS
3+
90
RE :LiYF4
SA
70
3
-1
Energy (10 cm )
80
VUV
60
SF
50
LS
40
HS
30
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
20
1
2
3
4
5
6
7
8
9
10
Number of 4f electrons
11
12
13
14
CONFIGURATIONAL CURVES
Crossluminescence and luminescence of selftrapped excitons
Luminescence Spectroscopy
Types of luminescence
Fast luminescence: fluorescence
Slow luminescence: phosphorescence
Luminescence excited by:
1) light: photoluminescence;
2) electron beam: cathodoluminescence;
3) ionizing radiation: radioluminescence;
4) heating: thermoluminescence;
5) electric current: electroluminescence
6) chemical reaction: chemiluminescence;
7) …
Typical shapes of emission
and excitation spectra
Stokes shift
Light sources
Continuum light sources - Deuterium lamp (200-600 nm), Rare gas continua
Gas
He
Ne
Ar
Kr
Xe
Line sources - Mercury lamps, Rare gas resonance line lamps
Lasers – Solid state, gas, other
Useful range (nm)
58 - 110
74 - 100
105 - 155
125 - 180
148 - 200
Synchrotron radiation
Characteristics of Synchrotron Radiation:
• Synchrotron radiation is highly collimated (within angle ~1/ = mec2/E)
• High brightness: synchrotron radiation is extremely intense (hundreds of thousands of
times higher than conventional X-ray tubes).
• Wide energy spectrum: synchrotron radiation is emitted within a wide range of
energies, allowing a beam of any energy to be produced.
• Synchrotron radiation is highly polarized.
• It is emitted in very short pulses, typically less than a nano-second.
• It’s spectral characteristics are calculable.
Synchrotron radiation – a perfect tool for material science
Properties of synchrotron radiation
35 / 2 e 2 c  E   c 
I   

  
16 2 R 3  mc 2    
7
3
4R  mc 2 
4R  1 

 
 
c 
3  E 
3   
3
3 
K  d

 
5/3
c
/
c (nm) 
 ~ 1 /   mc2 / E
0.559  R(m)
E 3 (GeV )
max  0.42c
Undulators
Wigglers
Characteristics of synchrotron radiation
from different magnet structures
SUPERLUMI set-up at HASYLAB
2-meter primary monochromator
3 secondary monochromators
PMT and position-sensitive detectors
• excit. energy 3.7-40 eV
• Time-resolved
measurements  500 ns
• absorption, reflection
• em=60-1000 nm
• T=5-800 K
• UHV
BW3 at HASYLAB
Spectroscopy using XUV excitation
• excitation energy 40-1500 eV
• Time-resolved
measurements  500 ns
• VUV SEYA-monochromator
• Fiber optics coupled UV-visible
spectrograph
• T=5-350 K
• UHV
MAX-III
• excitation energy 5-50 eV
• Time-resolved
measurements  10 ns
• VUV SEYA-monochromator
• Fiber optics coupled UVvisible spectrograph
• T=5-350 K
• UHV
SR Setups
Doris
MAX-III
Particle
e+
e
Energy
4.45 GeV
700MeV
Beam current
140 mA
280 mA
Circumference
289.2 m
36 m
Bunch Length
19.5 mm
Beamline stations
36
2
Insertion devices
9
2
Energy range
SUP – 3.7-40 eV
I3 – 5-50 eV
BW3 – 40-1500 eV
Resolving power
Photon flux on sample
I3 – 100 000
1012 ph/s/nm
I3 - 1011 - 1013 ph/s/0.1%bw
Cathodoluminescence Experimental Setup
• Liquid helium cryostat (5 – 400 K
temperature range) with LakeShore 331
Temperature Controller.
• Double VUV monochromator (4 – 12 eV
photon energy range). Johnson-Onaka
mounting, 1200 l/mm Al+MgF2 gratings.
Hamamatsu solar-blind photomultiplier
R6836.
• Double UV-VIS prism monochromator
(1.5 – 6 eV photon energy range).
Hamamatsu photon counting head H6240.
• Electron gun: 1 – 30 keV, 10nA - 1µA.
• LabView based data acquisition.
Photo- and cathodoluminescence
Photoluminescence
• very sensitive and selective
• nature of emission centres and excitation mechanisms
• fast and high throughput method
• non-destructive diagnostic method
Cathodoluminescence
• tuneable excitation depth
• sensitive for weak phenomena
• recharging of defects and traps
Scintillation detector
Main requirements to
scintillators:
(i) high density,
(ii) low cost,
(iii) high radiation
resistance
(iv) (iv) fast scintillation
decay .
Principles of PET
Ring of Photon
Detectors
 Patient injected with drug
having + emitting isotope.
 Drug localizes in patient.
 Isotope decays, emitting +.
 + annihilates with e– from
tissue, forming back-toback 511 keV photon pair.
 511 keV photon pairs
detected via time
coincidence.
 Positron lies on line defined
by detector pair (a chord).
Produces planar image of a “slice” through patient
LED
Schematic representation of a single plasma display cell, illustrating the process
of light generation.
Quantum splitting (quantum cutting) schemes
We need phosphor with Q > 100%
YAG:Ce phosphor-based white LED:
blue LED + yellow phosphor
Emission spectrum from YAG:Ce based
white LED
Dosimeters
Mechanism of thermoluminescence
Free
electrons
Conduction band
Diffusion
E
T
Trapped
electrons
and holes
L
T
L
Free holes
Bond electrons
Thermal
release
T
L
Light
Valence band
(1) Irradiation
(2) Storage
(3) Heating
MOBILITAS Postdoctoral
Research Grant
DEVELOPMENT OF NOVEL SCINTILLATORS BASED ON
THIN NANOCRYSTALLINE FILMS
SUPERVISOR – Marco Kirm
23.09.2011 – 22.09.2014
Objects of research
• Pure and RE doped HfO2 and ZrO2
1. Defects and traps in pure hafnia and zirconia
2. Intrinsic excitations
3. RE (Ce3+, Pr3+, Gd3+, Eu3+ etc.) in hafnia and zirconia.
4. Methods – ALD, PLD, sol-gel chemistry
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High-k material – HfO2 - 16-50, ZiO2-18-38, SiO2 – 3.9
High density - HfO2 – 11.78 g/cm3, ZiO2- 6.21 g/cm3
Possible control of crystallographic phases
Data from localized volume
Why to investigate and how to get
thin film scintillators ?
X-ray Microimaging application
- thin scintillators with high spatial resolution
- high effective Z values - high absorption
- efficient converters of X-rays
- Atomic layer deposition – two or more precursors
- ion implantation
Investigated Thin Films
Ion implanted films. D = 200nm
HfO2:Sm; HfO2:Eu; HfO2:Er – RE content = 40-500 ppm
ZrO2:Sm; ZrO2:Eu; ZrO2:Er
Multi-precursor-based films. D = 25nm
ZrO2:Er2O3 – Er content = 3-15%
Application
 Scintillators
 Microelectronic devices
 Protective layers
 Laser media
Conferences and Publications
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Harutunyan, V.V.; Saakyan, A.A.; Aleksanyan, E.M.; Grigoryan, R.P.; Hakobyan, G.R. Creation of Aluminium Nanolayer on a Corundum Monocrystals Surface by High-Energy
Electron Irradiation. International Conference “New technologies for development of heterosemiconductors for device applications. 2006, 65.
Lixin Ning, Peter A. Tanner, Vachagan V. Harutunyan, Eduard Aleksanyan, Vladimir N. Makhov, Marco Kirm. Luminescence and excitation spectra of YAG:Nd3+ excited by
synchrotron radiation. Journal of Luminescence, Volume 127, Issue 2, 2007, 397 - 403.
Aleksanyan Eduard, Harutunyan Vachagan, Kink Margarita, Kink Rein, Kirm Marco, Maksimov Yuri, Makhov Vladimir, Ouvarova Tatiana. Upconverted VUV 5d - 4f
luminescence of Er3+ doped into LiYF4 and BaY2F8 crystals under ArF-laser excitation. The 15th International Conference on Luminescence and Optical Spectroscopy of
Condensed Matter. Lyon, 7-11 July, 2008, 525.
Aleksanyan Eduard, Harutunyan Vachagan, Kostanyan Radik, Feldbach Eduard, Kirm Marco, Liblik Peeter, Makhov Vladimir, Vielhauer Sebastian. Luminescence and
excitation spectra due to inter- and intraconfigurational transitions of Er3+ in YAG:Er. The 15th International Conference on Luminescence and Optical Spectroscopy of
Condensed Matter. Lyon, 7-11 July, 2008, 336.
Aleksanyan Eduard, Harutunyan Vachagan, Kostanyan Radik, Feldbach Eduard, Kirm Marco, Liblik Peeter, Makhov Vladimir, Vielhauer Sebastian. 5d – 4f luminescence of
Er3+ in YAG:Er3+. International Baltic Sea Region conference “Functional materials and nanotechnologies 2008”, April 1-4, Riga, 2008, 38.
V.N. Makhov, A. Lushchik, Ch.B. Lushchik, M. Kirm, E. Vasil’chenko, S. Vielhauer, V.V. Harutunyan, E. Aleksanyan. Luminescence and radiation defects in electron-irradiated
Al2O3 and Al2O3:Cr. Nuclear Instruments & Methods in Physics Research B, Volume 266, Issues 12-13, 2008, 2949 - 2952.
Алексанян, Э.М. ВУФ люминесценция ионов Er3+ в кристаллах LiYF4 и BaY2F8. Известия НАН Армении. Физика // Journal of Contemporary Physics, 44(2), 2009, 113 118.
E. M. Aleksanyan. VUV Luminescence of Er3+ Ions in LiYF4 and BaY2F8 Crystals. Journal of Contemporary Physics (Armenian Academy of Sciences), 2009, Vol. 44, No. 2, pp.
75–79.
Eduard Aleksanyan, Vachagan Harutunyan, Radik Kostanyan, Eduard Feldbach, Marco Kirm, Peeter Liblik, Vladimir N. Makhov, Sebastian Vielhauer. 5d–4f luminescence of
Er3+ in YAG:Er3+. Optical Materials, Volume 31, Issue 6, 2009, 1038 - 1041.
Eduard Aleksanyan, Vachagan Harutunyan, Margarita Kink, Rein Kink, Marco Kirma, Yuri Maksimov, Vladimir N. Makhov, Tatiana V. Ouvarova. Upconverted 5d–4f
luminescence from Er3+ and Nd3+ ions doped into fluoride hosts excited by ArF and KrF excimer lasers. Optics Communications, Volue 283, Issue 1, 2010, 49 - 53.
E. Aleksanyan, M. Kirm, E. Feldbach, K. Kukli, S. Lange, I. Sildos, A. Tamm. Luminescence Properties of RE3+ Doped Hafnia and Zirconia Thin Films Grown by Atomic Layer
Deposition Method. International Conference “Functional materials and nanotechnologies 2012”, April 17-20, Riga, 2012, 50.
E. Aleksanyan, M. Kirm, S. Vielhauer, V. Harutyunyan. Investigation of Luminescence Processes in YAG Single Crystals Irradiated by 50 MeV Electron Beam. Lumdetr 2012 8th International Conference on Luminescent Detectors and Transformers of Ionizing Radiation. September 10-14, 2012, Halle (Saale), Germany, P-Tue-56.
Eduard Aleksanyan, Marco Kirm, Sebastian Vielhauer, Vachagan Harutyunyan. Investigation of Luminescence Processes in YAG Single Crystals Irradiated by 50 MeV
Electron Beam. Radiation Measurements 2013, In Press, Accepted Manuscript, DOI: 10.1016/j.radmeas.2013.01.036.
V. Nagirnyi, E. Aleksanyan, G. Corradi, M. Danilkin, E. Feldbach, M. Kerikmäe, A. Kotlov, A. Lust, K. Polgár, A. Ratas, I. Romet, V. Seeman. Recombination luminescence in
Li2B4O7 doped with manganese and copper. Radiation Measurements 2013, In Press, Accepted Manuscript, DOI: 10.1016/j.radmeas.2013.02.005.
Eduard Aleksanyan, Marco Kirm, Eduard Feldbach, Vitali Nagirnyi, Aarne Maaroos, Hugo Mändar. Luminescence Properties of Hafnia and Zirconia Nanopowders Prepared
by Solution Combustion Synthesis. International Conference “Functional materials and nanotechnologies 2013”, April 21-24, Tartu, Estonia, 2013, OR-25.
N.V. Vasil’eva, D.A. Spassky, I.V. Randoshkin, E.M. Aleksanyan, S. Vielhauer, V.O. Sokolov, V.G. Plotnichenko, V.N. Kolobanov, A.V. Khakhalin. Optical Spectroscopy of
Gd3(AlxGa1-x)5O12:Ce3+ Epitaxial Films. International Conference “Functional materials and nanotechnologies 2013”, April 21-24, Tartu, Estonia, 2013, OR-1.
Vachagan Harutunyan, Vladimir Makhov, Eduard Aleksanyan. X-ray Excited Emission of YAG and YAG:Nd3+ Single Crystals. International Conference “Functional materials
and nanotechnologies 2013”, April 21-24, Tartu, Estonia, 2013, PO-177.
Sebastian Vielhauer, Eduard Aleksanyan, Eduard Feldbach, Marco Kirm, Henri Mägi, Vitali Nagirnyi, Ergo Nõmmiste and Sergey Omelkov. VUV Photoluminescence
Spectroscopy Setup MAX III. International Conference “Functional materials and nanotechnologies 2013”, April 21-24, Tartu, Estonia, 2013, PO-187.
Thank You For Your Attention !
There is a continuous demand for efficient and durable luminescent materials
due to the rapid development of new applications like plasma displays, LED
emitters, solid state lasers and various scintillators. These applications are
frequently based on wide-gap materials activated with rare earth (RE) ions.
Wide band gap enables 4f transitions of RE3+ ions to emit within the optical
window of the host material and lets the host act as an efficient absorption
medium for the optical excitation in UV range. Even though the absorption
may occur in both the host and in the RE emission centre itself it is
more preferred to happen indirectly via host if we consider that the
concentration of RE ions does not usually exceed ~10 mol%
and the f-f
transitions have a forbidden nature. Higher RE concentrations would lead
to increasing cross-relaxation among ions which quenches the emission
considerably. Within the wide-gap materials the major attention has been
focused on various metal oxides because these materials are less sensitive to
oxygen surface contamination and also the preparation route of the
materials is relatively simple. The wide band-gap, high refractive index, good
transparency in visible spectral range and low phonon energies make titania,
zirconia, and hafnia increasingly popular hosts for doping with RE ions.