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1.
S. Nešpůrek 《Czechoslovak Journal of Physics》1999,49(5):859-870
Poly(organylsilylene)s with their uninterrupted chains of silicon atoms are a new class of materials with significant delocalization
of electrons along the polymer chain. Their electronic structure, optical properties, photoconductivity, electroluminescence,
and photorefractivity are discussed on the model compound poly[methyl(phenyl)silylene]. Their unusual electrical and optical
properties, such as high quantum generation efficiency, high charge-carrier mobility, efficient luminescence, and optical
non-linearity, can be utilized in some optoelectronic devices.
Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17,
1998.
This work was suported by the Grant Agency of the Academy of Sciences of the Czech Republic (grant No. A1050901) and by the
Grant Agency of the Czech Republic (grant No. 106/98/0700). 相似文献
2.
J. Walachová J. Zelinka J. Vaniš S. Karamazov M. Cukr P. Zich D. H. Chow T. C. McGill 《Czechoslovak Journal of Physics》1999,49(5):833-836
This work shows how ballistic electron emission microscopy and spectroscopy (BEEM/BEES) can be used for study of the tunneling
double barrier heterostructures. From positions of resonant levels follows that roughness at the interfaces is present. The
variation of the thickness of the well atributed to the existed roughness is estimated using simple calculation.
Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17,
1998.
This work is partly supported by the Grant Agency of the Czech Republic under grant No. 102/97/0427. 相似文献
3.
The composition of films deposited in RF glow discharge tubular reactor fed with tetraethoxysilane (TEOS) and oxygen mixtures at various temperatures, gas flows, gas pressures and various self-bias voltages were investigated by means of different diagnostic methods. The thickness, stress in thin films, hardness, composition and optical properties of deposited thin films were determined.The work was supported by the Grant Agency of the Czech Republic, grant No. 202/93/2118. 相似文献
4.
Vlastimil Matějec Miroslav Chomát Miloš Hayer Ivan Kašík Daniela Berková Fethi Abdelmalek Nicole Jaffrezic-Renault 《Czechoslovak Journal of Physics》1999,49(5):883-888
The paper summarizes results achieved in the Institute of Radio Engineering and Electronics in the field of investigation
and fabrication of novel fiber-optic structures for evanescent-wave chemical sensing. Several approaches for increasing the
evanescent-wave sensitivity of multimode silica optical fibers to gaseous and liquid chemicals are shown. These approaches
make use of the decrease of the core diameter in sectorial and capillary sectorial fibers, modification of trajectories of
optical rays in the cores of inverted-graded-index fibers, tailoring of the refractive index of porous layers applied on silica
cores, an output mode filter preventing the detection of rays propagating at low axial angles or fibers bent in single or
multiple turns.
Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17,
1998.
This work was supported by the Grant Agency of the Czech Republic (projects No. 102/96/0939 and No. 102/98/1358) and by joint
project No. 4104 of AS CR and CNRS, France. 相似文献
5.
A. L. Vikharev A. M. Gorbachev A. B. Muchnikov D. B. Radishchev 《Radiophysics and Quantum Electronics》2007,50(10-11):913-921
We study conditions for microwave plasma-assisted chemical vapor deposition of high-quality single-crystal diamond films in a CVD reactor. These conditions are studied using the results of homoepitaxial growth of polycrystalline diamond films on diamond substrates and on the basis of numerical simulation of the microwave discharge in a CVD reactor. A high-quality single-crystal diamond layer is synthesized on a synthetic, type Ib diamond substrate. The properties of the obtained monolayer are studied by means of Raman and X-ray diffraction spectroscopy as well as optical and atomic-force microscopy. 相似文献
6.
A. N. Obraztsov I. Yu. Pavlovskii H. Okushi H. Watanabe 《Physics of the Solid State》1997,39(10):1594-1598
Photoacoustic spectroscopy is used to study optical absorption in diamond powders and polycrystalline films. The photoacoustic
spectra of diamond powders with crystallite sizes in the range from ∼100 μm to 4 nm and diamond films grown by chemical vapor deposition (CVD) had a number of general characteristic features corresponding
to the fundamental absorption edge for light with photon energies exceeding the width of the diamond band gap (∼5.4 eV) and
to absorption in the visible and infrared by crystal-structure defects and the presence of non-diamond carbon. For samples
of thin (∼10 μm) diamond films on silicon, the photoacoustic spectra revealed peculiarities associated with absorption in the silicon substrate
of light transmitted by the diamond film. The shape of the spectral dependence of the amplitude of the photoacoustic signal
in the ultraviolet indicates considerable scattering of light specularly reflected from the randomly distributed faces of
the diamond crystallites both in the polycrystalline films and in the powders. The dependence of the shape of the photoacoustic
spectra on the light modulation frequency allows one to estimate the thermal conductivity of the diamond films, which turns
out to be significantly lower than the thermal conductivity of single-crystal diamond.
Fiz. Tverd. Tela (St. Petersburg) 39, 1787–1791 (October 1997) 相似文献
7.
We investigate the quasiparticle conformational defects (excitons, polarons and bioplarons) in the phenylene vinylene oligomers.
The conformations are determined by means of the minimization of the total Hartree-Fock energy calculated at 3–21G level.
The infrared vibrational transitions are calculated and the types of vibrations are assigned. The theoretical spectra are
in good agreement with the experimental vibrational spectrum of poly(p-phenylene vinylene).
Presented at the Czech-Israeli-German Symposium “Dynamical Processes in Condensed Molecular Systems”, Prague, Czech Republic,
26–30 May 1997.
The quantum mechanical calculations were performed on the following computers: Power Challenge XL at Prague Supercomputing
Centre, Charles University, IBM Power 2 at Supercomputing Centre of the Czech Technical University and Power Challenge XL
at Supercomputing Centre Brno.
The work is supported by Projects No. 202/94/0453 and 202/97/1016 of the Grant Agency of the Czech Republic and by Project
No. 155/96 of the Grant Agency of the Charles University. 相似文献
8.
In this paper we pursue the effect of the erbium and ytterium addition during the liquid phase epitaxial (LPE) growth on physical
properties of thin InP layers. Series of InP layer samples were prepared by LPE from the melts containing 0–0.3 wt.% of Er
and Yb. The grown layers were examined by the Hall effect andC-V measurements, photoluminescence spectroscopy and Rutherford backscattering spectrometry (RBS). We have found that only Yb
impurity was incorporated into the lattice of InP layer. With increasing Yb content in the growth melt the layer’s conductivity
smoothly changed from n to p type when Yb admixture exceeded certain limit. On the basis of these results we prepared p-n
junctions in the InP layers directly doped by Yb, and tested then byC-V measurements.
Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17,
1998.
This work has been supported by the Grant Agency of the Czech Republic, project No. 102/99/0341. 相似文献
9.
J. Musil D. Hovorka M. Mišina A. J. Bell V. Studnička 《Czechoslovak Journal of Physics》1998,48(8):963-971
We investigated the structure and composition of titanium carbide thin films deposited by the reactive magnetron sputter ion
plating process as a function of deposition parameters. The films were sputtered onto unheated glass substrates by means of
an unbalanced planar d.c. magnetron equipped with a titanium target using a mixture of argon and methane. The deposition parameters
ranged from 0.05 Pa to 2 Pa for total working gas pressurep
T, from 10% to 60% (volume) for relative methane concentration in the working gas mixture, from 45 mm to 85 mm for the substrate-to-target
distanced
s-t and from −50V to −800V for the substrate biasU
S. It was found that the crystallinity of the thin films strongly decreases with increasingp
T,d
s-t andU
S. The experiments described show the conditions necessary to obtain sputter-deposited nanocrystalline titanium carbide films.
This work has been partially supported by the Grant Agency of the Czech Republic under Grant No. 106/96/K245 and by the Ministry
of Education of the Czech Republic under Grant No. VS96 059. 相似文献
10.
Kinetic processes that influence epitaxial growth of thin films are being more and more explored. Recent observations of growth
on reconstructed surfaces suggested that material attachment to existing islands may be hindered by a barrier to attachment.
We present a kinetic Monte Carlo model of Si/Si(111)7×7 homoepitaxy with the barrier to attachment implemented. We show that
this model successfully reproduces available experimental results obtained during initial stages of growth and during surface
relaxation. We show that the high scaling exponents experimentally observed are due to specific growth kinetics of the Si/Si(111)7×7
system.
Presented at the VIII-th Symposium on Surface Physics, Třešt’ Castle, Czech Republic, June 28 – July 2, 1999.
This work was supported by the Grant Agency of the Czech Republic, project GAČR 202/97/1109 and by the Volkswagen Stiftung. 相似文献
11.
Š. Višňovský R. Lopušník M. Nývlt V. Prosser J. Ferré C. Train P. Beauvillain D. Renard R. Krishnan J. A. C. Bland 《Czechoslovak Journal of Physics》2000,50(7):857-882
This paper is a comprehensive study of different formalisms used to simulate polar magneto-optical (MO) effects in multilayers.
A development of the 4 × 4 matrix calculation to first order in off-diagonal elements of the permittivity tensor gives original
analytical expressions. They allow to express the MO effects in multilayers as a sum of contributions from individual layers.
Each contribution consists of two components assigned to the interface and propagation effects. The explicit expressions for
multilayers containing up to seven layers, together with those obtained in the frame of an ultrathin layer approximation,
are shown to be useful both in a qualitative comprehension and in quantitative simulations of the experimental MO Kerr spectra
of a wide variety of ultrathin magnetic structures. They can be used to separate the different contributions arising from
the interfaces due to intermixing or spin polarization (including interface roughness) as well as to simulate magnetically
coupled multilayers. As an example, the analytical expression is provided for a system consisting of two ultrathin films separated
by a non-magnetic spacer and deposited on a non-magnetic substrate. The capabilities of the analytical expressions are demonstrated
on MO spectroscopy in a broad spectral range of some well characterized ultrathin magnetic structures.
This work has been partially supported by HCM programme “Magnetic properties of novel ultrathin films” (project number ERBCIPDCT940622),
NATO Grant “High Technology” (LG931415) and Grant Agency of Czech Republic (# 202/97/1180 and # 202/00/0761). 相似文献
12.
A. Hospodková E. Hulicius J. Oswald J. Pangrác K. Melichar T. Šimeček 《Czechoslovak Journal of Physics》1999,49(5):805-811
Luminescence properties of strained In
x
Ga1−x
As/GaAs multiple quantum wells of different thickness and In content, prepared by metal organic vapour phase epitaxy were
studied. The influence of the quantum well material composition on the shape of luminescence spectra was investigated. The
experimental results were fitted by the Model Solid Theory. This fit was improved by the use of adjustedQ parameter.
Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17,
1998.
This work was supported by Grant Agency of Czech Republic under grants numbers 202/98/0074, 102/99/0414 and Grant Agency of
Academy of Sciences No. A 10110807/1998. 相似文献
13.
We report on liquid phase epitaxial growth of thick layers of GaInP(As) lattice matched to GaAs. Layers with thicknesses up
to 7 μm were prepared in multi melt bin, step-cooling, one-phase configuration. Unintentionally doped layers, grown from moderate
purity starting materials show significant decrease in the residual impurity level when erbium was added into the melt. Fundamental
electrical and optical properties of the layers were investigated.
Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17,
1998.
This work was partially supported by the Grant Agency of the Acad. Sci. CR under contract GAAV No. A 1010807/1998. 相似文献
14.
The article deals with the possibility to characterize the laser heat-treatment of steel surface by means of X-ray diffraction
and microhardness measurements. For tensometric analysis the X-ray one-tilt method with no reference substance was used. It
is shown that hardened surface layers of the carbon steel are affected by compressions reaching in the middle of the laser
beam track up to ≈ 350 MPa. The microhardness increased by as much as 350 %.
Presented at the 6th Joint Seminar “Development of Materials Science in Research and Education”, Karlštejn, Czech Republic,
17–19 September 1996.
This research is a part of the research project supported by Grant Agency of the Czech Republic (Grant No. 106/95/0080). 相似文献
15.
Spatially resolved measurements of vibrational and rotational temperature determined from the N2(C) nitrogen bands intensities have been performed by means of optical scanner of original construction. It has been found
that radial variations of studied bands are independent of pressure and discharge current under our experimental conditions,
i.e. in the pressure range (100–300) Pa and for discharge current up to 40 mA. Moreover, it has been found that vibrational
as well as rotational temperatures stay almost constant in the radial direction. No radial changes of both temperatures can
be explained by good thermal conductivity of the positive column of DC glow discharge.
This research was supported by grants: Charles University No. GAUK 194/01, Ministry of Education of Czech Republic MSM 11320002,
and Grant Agency of Czech Republic GAČR 202/03/0827. The theme of presented article was included in the EU project No. G1RT-CT-2002-05083
“Plasmatech”. 相似文献
16.
Photoconductivity in rigid polymers is based on complex processes including photo-induced electron transfer, formation of
ion pairs and their dissociation in an external electric field. Thus, the charge carrier photogeneration in macromolecules
differs largely from the direct band-gap excitation and the formation of free electrons and holes in inorganic materials.
The processes mentioned above were studied on a catena silicon polymer, namely poly(methyl-phenylsilylene).
Presented at the Czech-Israeli-German Symposium “Dynamical Processes in Condensed Molecular Systems”, Prague, Czech Republic,
26–30 May 1997.
This work was supported in part by the Grant Agency of the Academy of Sciences of the Czech Republic (Grant No. 45007). Additional
support was provided in the framework of the Bilateral Scientific-Technical Cooperation between the Czech Republic and Federal
Republic of Germany, project Photo/Electro-Respondent Materials (KONTAKT, No. ME 087 and FKZ-Nr. TSR-005-95). 相似文献
17.
Laser polishing of diamond plates 总被引:5,自引:0,他引:5
S.M. Pimenov V.V. Kononenko V.G. Ralchenko V.I. Konov S. Gloor W. Lüthy H.P. Weber A.V. Khomich 《Applied Physics A: Materials Science & Processing》1999,69(1):81-88
Results are reported on laser polishing of 150–400-μm-thick free-standing diamond films with either a copper vapor laser (510 nm
wavelength) or an ArF excimer laser (193 nm wavelength). Studies were focused on three particular goals. First, we aimed at
a choice of optimum conditions for laser polishing of thick diamond films. It was shown that the laser polishing conditions
and the resulting surface roughness were controlled by varying the angle of incidence of a scanning laser beam and by polishing
time. Second, the laser ablation technique was applied to remove a defective layer from the “substrate” side of the diamond
plates in order to reduce optical losses due to absorption in this layer. Third, the structure of the laser-graphitized diamond
surface was studied using UV, visible, and IR optical spectroscopy techniques in the course of the “step-by-step” oxidative
removal of the graphitic layer with increasing temperature of the oxidation in ambient air. Once the graphitic layer was removed,
the optical transmission in the UV-visible-IR spectral range of the diamond films polished under optimum conditions was measured
and compared with the optical transmission of the mechanically polished diamond films. It was shown that the optical quality
(in the long-wave infrared region) of the laser-polished diamond plates was sufficient to reach the transmittance value very
close to the theoretical limit.
Received: 20 October 1998 / Accepted: 8 March 1999 / Published online: 5 May 1999 相似文献
18.
The promising applications of the microwave plasmas have been appearing in the fields of chemical processes and semiconductor
manufacturing. Applications include surface deposition of all types including diamond/diamond like carbon (DLC) coatings,
etching of semiconductors, promotion of organic reactions, etching of polymers to improve bonding of the other materials etc.
With a 2.45 GHz. 700 W, microwave induced plasma chemical vapor deposition (CVD) system set up in our laboratory we have deposited
diamond like carbon coatings. The microwave plasma generation was effected using a wave guide single mode applicator. We have
deposited DLC coatings on the substrates like stainless steel, Cu-Be, Cu and Si. The deposited coatings have been characterized
by FTIR, Raman spectroscopy and ellipsometric techniques. The results show that we have achieved depositing ∼95% sp3 bonded carbon in the films. The films are unform with golden yellow color. The films are found to be excellent insulators.
The ellipsometric measurements of optical constant on silicon substrates indicate that the films are transparent above 900
nm. 相似文献
19.
P. Cluzeau F. Bougrioua G. Joly L. Lejček H. T. Nguyen 《Czechoslovak Journal of Physics》2004,54(3):365-376
A simplified model of an inclusion represented by (+1)-wedge disclination and an accompanying hyperbolic defect ((−1)-wedge
disclination) in smectic C* free standing films is used to describe the early stage of the ordering process of inclusions
into chains. The elastic interaction between inclusions and their associated hyperbolic defects is used to discuss the dynamics
observed experimentally during the inclusion chaining when inclusions are at distances much larger than their radii.
This work was also supported by Grant No. 202/02/0840 of the Grant Agency of the Czech Republic and by the research project
AV0Z1-010-914. 相似文献
20.
J. Kudrnovský V. Drchal I. Turek C. Blaas P. Weinberger P. Bruno 《Czechoslovak Journal of Physics》1999,49(11):1583-1589
The current-perpendicular-to-plane (CPP) magnetoconductance of a trilayer consisting of a spacer sandwiched between two ideal
leads is described on anab initio level. We employ the transmission matrix formulation of the conductance within the framework of the spin-polarized surface
Green function technique as formulated in terms of the tight-binding linear muffin-tin orbital method. The formalism is extended
to the case of lateral supercells in each layer with random arrangements of atoms which allows to treat both the ballistic
and diffusive transports on equal footing. The application is made to fcc-based Co/Cu/Co(001) trilayers.
Presented at the VIII-th Symposium on Surface Physics, Třešt’ Castle, Czech Republic, June 28 – July 2, 1999.
Financial support for this work was provided by the Grant Agency of the Czech Republic (Project No. 202/97/0598), the Grant
Agency of the Academy of Sciences of the Czech Republic (Project A1010829), the Center for the Computational Materials Science
in Vienna (GZ 45.442 and GZ 45.420), the Austrian BMWV (AKTION WTZ-?sterreich-Tschechien I.23), MŠMT ČR (Project COST P3.70),
and the TMR Network ‘Interface Magnetism’ of the European Commission (Contract No. EMRX-CT96-0089). 相似文献