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91.
Ladislav Štourač 《Czechoslovak Journal of Physics》1959,9(6):717-720
, Bi2Te3-Bi2Se3. , , , . .
Influence of ageing on change in electrical properties of semiconducting systems of Bi2Te3-Bi2Se3
The paper describes the effect of ageing observed on a semiconducting system Bi2Te3 — Bi2Se3. It is shown that the change in electrical conductivity and thermoelectric force, which takes place during ageing, is caused by the change in concentration of the free electrons. The influence of this process on the efficiency of equipment employing the Peltier effect is analyzed.相似文献
92.
Electrical and electrochemical properties of solid LiH2PO4 conductor were investigated in the temperature range from room temperature to 373 K. It was found that high conductivity throughout the temperature range, with activation energy 17.23 kJ/mol, originates from the movement of hydrogen ions (protons). The movement of protons in the correlation with phosphate groups rotation was considered. The slopes of Tafel lines and exchange current densities both for cathodic hydrogen and anodic oxygen evolution were determined (by means of usual electrochemical kinetic methods) at various temperatures. The energy of activation at the equilibrium potentials both for the cathodic and the anodic processes have been assessed to be 17.23 kJ/mol (0.18 eV) and 2.9 kJ/mol (0.03 eV), respectively. 相似文献
93.
Z. Šroubek 《Surface science》1974,44(1):47-59
The process by which atoms are ionized as they are sputtered from a metal surface has been analyzed both theoretically and experimentally. In the theoretical part the expressions for ionization coefficient R+ of atoms having the ionization energy much larger than the metal work function have been derived using a molecular orbital method. The effect of the level crossing was estimated in an approximate way. In the experimental part the SIMS experiments on clean Ni and Al surfaces and on Ni surface covered with a submonolayer of adsorbed K, Na and Al are reported. It has been found and it is for the first time reported that the energy distribution of ions sputtered from a submonolayer of adatoms is independent of energy (200–2500 eV) and mass (Ar+ Xe+ of incident ions and depends only upon the adsorption energy of the adatom. The energy distribution of ions sputtered from bulk samples has been found dependent on the primary ion energy. The measurement of the absolute value of R+ has shown that there is a strong correlation between the number of the adatom valence d-electrons and the value of R+, the value of R+ being smaller for atoms with more d-electrons. These experimental data have been compared with the theoretical expressions and the important role of the mechanism which takes into account the bending of the adatom energy level has been assessed. 相似文献
94.
Miroslav Engliš 《Journal of Fourier Analysis and Applications》2007,13(3):243-265
Toeplitz operators on the Bergman space of the unit disc can be written as integrals of the symbol against an invariant operator
field of rank-one projections. We consider a generalization of the Toeplitz calculus obtained upon taking more general invariant
operator fields, and also allowing more general domains than the disc; such calculi were recently introduced and studied by
Arazy and Upmeier, but also turn up as localization operators in time-frequency analysis (witnessed by recent articles by
Wong and others) and in representation theory and mathematical physics. In particular, we establish basic properties like
boundedness or Schatten class membership of the resulting operators. A further generalization to the setting when there is
no group action present is also discussed, and the various settings in which similar operator calculi appear are briefly surveyed. 相似文献
95.
Karen Avetisyan Miroslav Pavlovi? 《Journal of Mathematical Analysis and Applications》2007,336(1):31-43
It is proved that the inequality δX(ε)?cεp, p?2, where δX is the modulus of convexity of X, is sufficient and necessary for the inequality
96.
97.
J. Kudrna I. Pelant J. Štěpánek F. Trojánek P. Malý 《Applied Physics A: Materials Science & Processing》2002,74(2):253-256
We have studied ultra-fast carrier dynamics of photo-excited carriers in hydrogenated microcrystalline silicon prepared by
a very high frequency glow-discharge technique. We report on direct observation of two types of dynamics using selective photo-excitation
in picosecond pump and probe measurements. One type of the observed dynamics has been found to be independent of the sample
preparation, while the other reflects the relative weights of crystalline and amorphous fractions. We propose a simple rate-equation
model that describes the carrier dynamics in microcrystalline silicon in terms of the composition of those in Si microcrystallites
and in the a-Si:H tissue which surrounds the microcrystallites. The model without any fitting parameters reproduces the experimental
data very well when the dynamics are scaled with relative volume fractions as obtained from Raman spectra.
Received: 23 November 2000 / Accepted: 17 March 2001 / Published online: 23 May 2001 相似文献
98.
In this paper, based on the Hermitian and skew-Hermitian splitting, we give a generalized modified Hermitian and skew-Hermitian splitting (GMHSS) method to solve singular complex symmetric linear systems, this method has two parameters. We give the semi-convergent conditions, and some numerical experiments are given to illustrate the efficiency of this method. 相似文献
99.
Jan Wild Jiří Macl Hana Šíchová Pavel Boháček Jarmila Prachařová Pavel Kubát Svatopluk Civiš 《Czechoslovak Journal of Physics》1997,47(10):1025-1030
Bi(Pb)–Sr–Ca–Cu–O layers were prepared by laser ablation in air, that is without using a vacuum chamber. At this method a much higher density of pulse energy of laser beam is required (10–30 J cm–2) in comparison with the standard method (1–3 J cm–2). The mentioned condition has specific effects on the nature of the transport of material from the target. As follows from the electron microprobe analysis of the layers, the starting composition of the transported material is identical with that of the superconducting phase sintered in the target; one exception represents Pb, the content of which in the transported material is lower. The image of the process is complemented by UV/VIS spectroscopy scans of the plasma plume. 相似文献
100.
The acetone molecule is investigated in its ground state and valence 1,3n-π*, 1,3π-π*, and 1,3σ-π* excited states and Rydberg 1,3n-3s, 1,3π-3?, 1,3n-3py and 1,3π-3py states using the CASSCF, CASPT2, and CCSD(T) methods. Equilibrium geometries of excited states are obtained and their changes with respect to the ground state are discussed. For most excited states the C2v symmetry of the ground state is lowered to the Cs symmetry. A series of valence vertical and adiabatic excitation energies is presented along with excitation energies for Rydberg states. The main body of the paper contains Finite-Field Perturbation Theory (FFPT) calculations of electric properties of the vertically as well as geometry relaxed excited states. Dipole moments of valence excited states decrease significantly upon excitation, being about one half of the ground state dipole moment. Polarizabilities usually change upon excitation much less (increase by about 30%) but hyperpolarizabilities are enhanced up to one or two orders of magnitude. The orientation of the dipole moment is reversed in some vertically excited Rydberg states. Properties of the ground and excited states are discussed considering alterations of the electronic structure and shifts in the geometry. 相似文献