TF6.P - ICTF 12

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TF6:
Micropattering and Nanostructures
Posters
TF6.1.P
Production of Nanocrystalline TiO2 Films with Controlled Structure
by Aerodynamically Filtered Cluster Deposition
E. Barborini1, I. N. Kholmanov1 P. Piseri1, C. Ducati2, C.E. Bottani3, P. Milani1*
1
INFM-Dipartimento di Fisica, Universita’ di Milano, Via Celoria 16, I-20133 Milano,
Italy
2
Department of Engineering, University of Cambridge, Cambridge, UK
3
INFM-Dipartimento di Ingegneria Nucleare, Politecnico di Milano, I-20133 Milano,
Italy
We have produced nanocrystalline titanium dioxide films with different structure
(anatase or rutile) by depositing mass selected clusters from the gas phase.
Nanoparticles are produced by a pulsed microplasma cluster source and selected by
aerodynamic separation effects. We have characterized nanocrytalline films by Raman
spectromicroscopy and transmission electron microscopy showing that the films
assembled with clusters with diameter smaller than roughly 5 nm have a rutile phase
whereas larger clusters form films with anatase structure. The film nanostructure can
be chosen only by selecting and depositing clusters with different dimensions without
any thermal annealing or post-deposition treatment. Our observations suggest that
phonon confinement effects are responsible for a significant shift and broadening
observed for the Raman peaks.
The low temperature involved in the deposition process is interesting for the
production of films on thermolabile substrates and filters to be used for photocatalysis,
antibacterial coatings and water purification.
TF6.2.P
ANALYSIS OF SURFACE MODIFICATION OF FLAT Si
SUBSTRATE BY ENERGETIC Ti CLUSTERS
R. Diaz 1, E. Camps 1, L. Escobar-Alarcón 1, J. A. Ascencio2,* and R. López-Castañares 3
1
Departamento de Física, Instituto Nacional de Investigaciones Nucleares, Apartado
postal 18-1027, México DF 11801, México
2
Instituto Mexicano del Petróleo, Coor. Inv. y Des. de Ductos. Eje Central Lazaro
Cardenas 152, Mexico D.F. 07730, México
3 U.A.E.M, Edo. de México, México
One of the most important tools in the production of thin films is the laser ablation
technique, based on the covering of substrates controlling the energy of particles which hit
the substrate. This method is well studied, however many questions are still unanswered,
one of them is the surface deformation, produced in crystalline substrates during the film
growth. In this work we report the characterization of the plasma plume formed by laser
ablation of a TiO2 target, by means of time of flight optical emission spectroscopy, using an
intensified CCD camera. These measurements showed the presence of high energy (~ 500
eV) particles. Ablation of the target was carried out using a Nd:YAG laser, with emission at
the fundamental line. The characterized plasma regimes were used to deposit nanoparticles
over a Si based flat substrate, at different working pressures. Analysis of the substrate
surface by SEM and AFM showed the presence of embedded particles in the substrate
matrix. Using back scattering, which allowed a compositional contrast, we analyzed
transversal views that helped to identify the corresponding depth of clusters deposition and
holes in the substrates. The use of tapping, phase and force modulation in AFM, allowed
two and three dimensional analysis of the clusters and their surround sections which present
particularly interesting morphologies and material distributions.


Corresponding author *: Tel 52 55 30036424; Fax. 52 55 30036414; E-mail: [email protected]
Instituto Mexicano del Petróleo, Coor. Inv. y Des. de Ductos. Eje Central Lazaro Cardenas 152, Mexico
D.F. 07730, México
2
TF6.3.P
ION-BEAM ETCHING OF RAMPS IN THIN FILM
HETEROSTRUCTURES
Peter B. Mozhaev, Philippe V. Komissinskii, Julia E. Mozhaeva
Institute of Radio Engineering and Electronics RAS, 101999, Moscow, Russia,
Dept. of Microelectronics, Chalmers University of Technology, SE-41296, Sweden
Ion-beam patterning of thin films and heterostructures is one of the most common
processes of fabrication of thin film devices and structures. "Directed" nature of ion-beam
etching provides a possibility to form certain profiles on the films surface, like shallow
ramps, when etching is performed at some inclination angle. A simple geometrical model is
presented, describing the formation of a ramp as a shadow of the mask on the film surface.
Good agreement with the experiment can be obtained if the mask etching is taken into
account. The etching at the opposite direction ("high-angle etching") also can be
satisfactory described by the model. The profile of the slope - positive or negative
curvature, pits near the end of the ramp - is discussed as a function of the etch rate
dependence on the incidence angle. Such etch rate dependences for some often used
materials were measured. An area of instability of the resulting ramp shape is found for the
"high-angle etching". The model is compared with the experimental data reported by other
groups. Finally ion-beam etching of a rotating sample at non-normal incidence is discussed,
the results are compared with experimental data.
The work was supported in part by the RFBR grant 01-02 17990-a, Young scientists
commission of RAS grant #393, and INTAS project 01-0249.

Corresponding author:
Peter B. Mozhaev,
Institute of Radio Engineering and Electronics RAS,
Mokhovaya str., 11, bldg.7
101999, GSP-9, Moscow,
Russian Federation
Phone: (7 095) 203 0935
Fax: (7 095) 203 8414
E-mail: [email protected]
TF6.4.P
PATTERNING OF HIGH TEMPERATURE SUPERCONDUCTING
THIN FILMS FOR SUBMICRON WEAK LINKS AND DEVICES
Zs.Öszi, Š.Beňačka, Š.Chromik, V.Štrbík, Š.Gaži, I.Kostič*
Institute of Electrical Engineering, SAS, *Institute of Informatics, SAS
High temperature superconducting nanostrips down to 200nm width have been fabricated
from about 100nm thick YBa2Cu3Ox (YBCO) thin films. The patterning process detoriates
the transport properties of nanostrips resulting in structural damage and oxygen loss. The
most crucial steps are the baking procedures of optical or electron beam resist, the resist
development and ion beam etching process. The irreversible damage may be attributed to
structural disorder caused by ion beam etching (in our case about 80nm on each side of the
microstrip) and chemical reactions (with H2O, CO2). The reversible damage is
characterized by oxygen loss because the ion energy during etching is high compared to the
binding energy of the chain oxygen atoms. By optimizing the patterning steps and applying
post-treatment procedures we have been able to achieve superconducting transition
temperature of nanostrips above 80K and critical current density jc at 4K up to 107A/cm2.
The temperature dependence of YBCO critical current density was estimated from currentvoltage characteristics of samples placed in a magnetically shielded volume. The
comparison with theoretical Ginzburg-Landau depairing critical current density shows that
experimental values are several times smaller probably a result of granularity of films and
the effective width of the microstrips is smaller than geometrical one due to a depression of
superconductivity at the edges of the microstrip. In spite of the damage the prepared
microstrips are convenient for thin film superconducting structures and weak links of
submicron dimensions.

Š. Beňačka, Institute of Electrical Engineering, SAS, Dúbravská cesta 9, 84239
Bratislava, Slovakia, Tel.; (+4212)54775820, ext.2139, Fax.; (+4212)54775816, E-mail:
[email protected]

Corresponding author *: Tel.; Fax.; E-mail:
Give full address details of the corresponding author at the bottom
TF6.5.P
MONTE-CARLO SIMULATION OF ELECTRON INTERACTION
WITH A THIN FILM
Vladimír Starý, Fac. of Mech. Engn., CTU Prague, Karlovo nám. 13, 121 35 Prague 2,
Czech Republic
A Monte-Carlo simulation (MC) of fast electron transport in solids can give us
reasonable results in electron microscopy, spectroscopy and microanalysis, where
knowledge of certain quantities is very often needed for proper analytical measurement.
One of the most important parameters is the size of the volume where the interaction of
electrons with matter produces X-ray radiation. This quantity is important mainly when
evaluating the composition of non-homogeneous samples, e.g., thin films on a substrate and
particles in a matrix. Elastic and inelastic collisions are usually considered as the basic
interactions of primary electrons with atoms. Sometimes surface interactions are also
included. We prepared the Monte Carlo code to simulate this interaction. In our MC code,
the single scattering model is employed. The reliability of physical models incorporated in
a Monte-Carlo simulation is usually checked, where possible, by comparing calculated
values with experimental ones; unfortunately, some quantities are very difficult to measure.
Using our Monte-Carlo code, we calculated both the electron backscattering
coefficient and X-ray production in thin films of Au on the Si substrate. The electron beam
energy was in the range 1 - 30 keV, i.e., in the range used in SEM. The film thickness was
in the range 0.05 - 0.5 m for a thin Au film. The MC data of backscattering can be
compared with the experimental values, but the dimensions of the interaction volume can
be measured only indirectly and with relatively low precision; thus, more or less precise
semi-empirical formulas are usually used. We calculated the dependences of the
backscattering coefficient on the energy of the electrons and on the film thickness.
Reasonably good agreement was found between calculations and experiments. In addition
to X-ray intensities and peak/background ratios, both radial and depth profiles of X-ray
production in the sample were calculated. In this way, the dependences of the maximum
depth of X-ray production and of the diameter of the interaction volume will be presented.
TF6.6.P
Fabrication of Silicon nanostructures by UHV-STM lithography
in Self-Assembled Monolayers
M. Sundermann, A. Brechling, K Rott, D. Meyners ,U. Kleineberg, U. Heinzmann
University of Bielefeld, Faculty of Physics, Universitaetsstr. 25, D-33615 Bielefeld,
Germany
A. Knüller, W. Eck, A. Gölzhäuser, M. Grunze
University of Heidelberg, Applied Physical Chemistry, 69120 Heidelberg, Germany
The fabrication of nanostructures with lateral dimensions down to a few nanometers in
single-crystalline silicon substrates is a key technology for many applications ranging from
nanoelectromechanical devices (NEMS) to nanofluidic systems for biological applications.
High resolution lithography as provided by direct e-beam writing or scanning probe writing
in suited resists in combination with optimized dry or wet etch procedures for pattern
transfer are among the most promising techniques for the fabrication of arbitrary shaped
nanostructures in various materials.
Our approach utilizes UHV-STM writing in Self-Assembled Monolayers (SAM). SAMs
form highly-ordered ultrathin (~2-3 nm) monomolecular layers ontop of preactivated
Si(100) or Si(111) surfaces. After patterning by UHV-STM writing in constant-current
mode at different write parameters (gap voltage, electron dose) the modified SelfAssembled Monolayer serves as an etch mask for an anisotropic wet etch transfer (two-step
etch process in aqueous solutions of 5 % HF and 1 M KOH), of the write structure into the
silicon substrate. The corresponding silicon nanostructures have been analyzed afterwards
by AFM or SEM to characterize the pattern accuracy.
We have studied the suitability of three different types of SAMs on silicon single-crystals :
Alkylchain-type SAMs like Octadecylsilane (ODS) monolayer have been formed by
immersion of hydroxilated Si(100) in Octadeclytrichlorosilane (CH3(CH2)17SiCl3) while
SAMs with aromatic spacer groups such as Hydroxybiphenyl (HBP, (C6H6)2OH) and
Ethoxybiphenylsilane (EBP, (C6H6)2O(CH2)3Si(OCH3)3) are formed on Si(111).
Depending on the applied write parameters, significant differences in SAM resist
modification (e.g. positive tone vs. negative tone) have been found and models of the
underlying write process are proposed. The implications of the azimuthal orientation of the
resist pattern with respect to the underlying crystal structure are also discussed.
The minimum line width which could be achieved in dense line patterns with an etch depth
of about 30 nm, are around 35 nm in Si(100) and in the range of 26-31 nm for Si(111). The
edge accuracy of the line patterns has been measured to be about 5-7 nm displaying the
excellent high-resolution capability of the process.
Corresponding Author : [email protected],
phone 0049 521 106 5480, fax 0049 521 106 6001
TF6.7.P
FABRICATION AND STRUCTURE CHARACTERIZATION OF
NANOCRYSTALLINE SILICON FILMS PREPARED BY PECVD AS
A POSSIBLE SUBSTRATE MATERIAL FOR CARBON NANOTUBES
FORMATION
V.Vikulov,1 B.Hong,2 Y.H.Roh,2 J.S.Yi,2 C.S.Park2
[1] Kiev National Taras Shevchenko University, Kiev, Ukraine,
[2] Sungkyunkwan University, Suwon, South Korea.
Porous silicon (PS) is a promising candidate for growing well-aligned carbon
nanotubes (CNT), because of its appropriate surface structure and important physicochemical properties [1, 2]. Here we report the results of investigation of deposition
condition and some properties of nano-crystalline silicon (nc-Si) films as a possible
substrate material for CNT formation.
Nano-crystalline Si films were deposited by low temperature rf plasma enhanced
chemical vapor deposition (PECVD) technique using SiH4/H2 gas mixture onto Si wafers.
Structure and composition of nc-Si films were studied using atomic force microscopy
(AFM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR)
techniques.
The AFM data shows the nano-sized columnar structure of the films surface. At the
same time internal microstructure of these films consists of nano-sized Si crystals. FTIR
investigation revealed different vibrational modes related to Si-Si, Si-Hn, Si-O bonds within
the films. Taking to account the intensities of corresponding vibrational bands one can
conclude that the film is formed of Si nano-crystallites of which surface atoms are bound
with the oxygen and hydrogen. Such type of nc-Si film structure is close to that of porous
silicon.
Comparison of the surface structure of nc-Si obtained in our investigation with that
of anodically etched PS has shown their similarity. Taking into account the advantages of
production of large-scale nc-Si films with uniform surface structure we may conclude that
nc-Si films can be used as a substrate material for deposition of well-aligned CNT.
References:
1. S Fan et al., Physyca E, 8 (2000), 179
2. J Sohn et al., Appl. Phys. Lett., V78, 7 (2001), 901
--------------------------Corresponding author: Viktor Vikulov; Tel.: +82-31-290-7209; Fax: +82-31-290-7191
E-mail: [email protected]
Address: Electrical and Computer Engineering Dept., Sungkyunkwan University, 300
Chunchun Dong, Jandan-Gu, Suwon, Kyunggi-do 440-746, Korea
TF6.8.P
PREPARATION OF POLYMER/METALLIC NANOPARTICLES BY
THE INVERSE MINIEMULSION
I.Capek1) and E.Majkova2)
1) Polymer Institute, Slovak Academy of Sciences, , 842 36 Bratislava
2) Institute of Physics, Slovak Academy of Sciences, , 842 28 Bratislava
The preparation of nanosized metallic particles (aggregates) for use in various fields
of science and technology is of great interest in nowadays. For example, the development
of a high density magnetic memory device may be readily achieved by patterning magnetic
nanoparticles into organized assembly on the surface of a substrate. An increasing popular
method of preparing nanoparticles takes advantages of micellar aggregates of metal salts
and stabilizer in organized aggregates. By controlling the amounts of stabilizer in water or
the ratio stabilizer/water, the inverse microemulsion affords great control over the size and
the shape of nanoparticles.1) The main advantages of chemical synthesis of metallic
particles in the inverse micellar systems are their low colloidal stability and the broad size
distribution of metallic particles. The stability of such particles can be increased by
additional increase in concentration of stabilizer. The somewhat coarse dispersion is the
result of a strong interparticle interaction and flocculation. Furthermore, this may also lead
to the heterogeneous distribution of metal ions within the microdroplets and the presence of
metallic particles and unnucleated microdroplets. We are developing a new version of
chemical synthesis of metallic or polymer/metallic nanoparticles by the inversion
minemulsion or miniemulsion polymerization. The miniemulsion is known to prepare the
highly stable polymer particles with a narrow particle size distribution using the small
amount of stabilizer.2) This version, thus, differs from the known ways of particle synthesis
in inverse micelles in that way the particle size and distribution are controlled by simple
mechanical homogenization of aqueous phase in the organic phase in the presence of a
relatively small amount of stabilizer. Furthermore, this method secure the homogeneous
distribution of reactants in all aqueous minidroplets and the similar interaction among all
minidroplets. The addition of costabilizer (water-soluble monomers and polymers) and the
high degree of homogenization decrease the particle flocculation and the Ostwald ripening.
With respect of the nature of reducing agents or reducing process, chemical methods may
be subdivided into classical chemical and radiation-chemical.3) In this study we induce a
modified chemical method where the reduction process is initiated by radicals generated
by decomposition of initiator and the propagating radicals generated during the
polymerization. This reduction process was very efficient in the cyclohexan/Tween
85/acrylamide/FeCl3/water miniemulsion where the formed metallic particles precipitated
from the system during the polymerization. Thus, the reaction of ferric ions with radicals
led to the formation of metal particles. However, the unstable colloidal system was
supposed to lead to the particles with different particle sizes and broad particle distribution.
The hydrophilic polymer formed during the polymerization is supposed to act as
costabilizer and increases the stability of final polymer/metallic particles. However,
polyacrylamide itself failed to stabilize metallic particles. The mre stable polymer/metallic
dispersions were formed in the cyclohexan/Tween 85/acrylamide/NiCl2/water
miniemulsion. The addition of methacrylic acid increased much more colloidal stability of
final particles. In this case, the reduction of NiCl2 was not total and therefore the final
dispersion was treated with the aqueous solution of classical reducing agent sodium
borohydride to finish reducing of metal ions. The diameter of final polymer/metallic
particles was observed to decrease with increasing stabilizer (Tween 85) concentration:
D(nm)/Tween 85 x 102(mol.dm-3): 266/2.72, 232/5.44, 202/8.15, 181/10.9. 158/13.6.
Furthermore, methacrylic acid (MA) was found to slightly decrease the particle size up to a
certain critical concentration: D(nm)/MA(g/100 g cyclohexane):235/0.5, 202/1.2, 210/2,
198/3, 369/5. The addition of methacrylic acid strongly increased stability of both monomer
and polymer/metallic dispersion.
Literature:
1) M.P.Pileni, J.Phys.Chem. 97, 6961 (1993)
2) C.M.Miller, E.D.Sudol, C.A.Silebi, Macromolecules 28, 2772 (1995)
3) E.M.Egorova, A.A.Revina, Colloids and Surfaces, 168, 87 (2000)
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