bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phonon Scattering in Plastically Deformed Ge
Authors: Singh S. R. , Singh S. 
Published: July 2007

AbstractThe measurements of Sato and Sumino on the low temperature phonon conductivity of plastically deformed germanium single crystals are analysed quantitatively using a cooperative model for the scattering of phonons by static and vibrating dislocations. The discrepancies observed between the experimental and theoretical results around 20 and below 2.2 K are resolved by considering the scattering of phonons by dislocation induced point defects and by modifying the value of phonon scattering by crystal boundaries, respectively.
Chemical Shifts of Auger Lines in Solids on the Example of the KL23L23 Transition in Silicon and Its Compounds
Authors: Fellenberg R. , Streubel P. , Meisel A. 
Published: July 2007

AbstractThe line position of the Si KL23L23 Auger transition is measured in silicon, silicon carbide, silicon nitride, silicon dioxide, and sodium hexafluorosilicate. The chemical shifts with reference to silicon are estimated and compared with the corresponding shifts of photoelectron peaks of Si 1s and Si 2p. The change of the extra‐atomic static relaxation energy ΔRsea determined in this way is proportional in first approximation to Pauling's electronegativity. The described method makes possible to estimate parameters of bonding in atomic ranges in solids containing silicon.
Relaxation of Interband Disturbances. A Phenomenological Theory
Authors: Allen P. B. 
Published: July 2007

AbstractA recent phenomenological theory of Garik and Ashcroft (GA) is generalized to permit interband electron–hole pairs to couple to intraband pairs. The enlarged theory differs in important respects from GA theory and corresponds closely to the microscopic theory of Chakraborty and Allen. The theory is explicitly solved for σ(ω), and the corrections to Boltzmann dc transport are discussed. The new theory has an additional parameter, the phase of the interband–intraband coupling constant η, which cannot be eliminated a priori.
Carrier Statistics in Zero‐Gap Semiconductors in the Presence of a Quantizing Magnetic Field
Authors: Chakravarti A. N. , Ghatak K. P. , Rao G. B. , Ghosh K. K. 
Published: July 2007

AbstractAn attempt is made to formulate the carrier statistics in zero‐gap semiconductors in the presence of a quantizing magnetic field. Numerical computations are done taking n‐HgTe as an example. It is concluded that the electron–electron interactions significantly affect the carrier statistics in such semiconductors, particularly at relatively low values of the electron concentration, i.e. under pure and lightly doped conditions at relatively low values of the temperature.
An Interatomic Pair Potential for Aluminium Calculation of Stacking Fault Energy
Authors: Rautioaho R. H. 
Published: July 2007

AbstractA potential function for aluminium is derived from phonon dispersion curves. The contribution from short‐range multi‐ion interactions is substracted from the phonon data, and this affects markedly the short‐range characteristics of the potential. The potential function is used for the calculation of the energies of intrinsic and extrinsic stacking faults. Certain multi‐ion contributions to these energies are also evaluated. The calculation cannot explain the experimentally observed difference between γintr and γextr, which is attributed here to the interpretation of loop annealing observations in such faults. A re‐interpretation gives approximately 120 mJ/m2 for γintr and γextr.
ESR and Optical Absorption Studies of ClO3 in Ba(ClO4)2 · 3H2O Single Crystals
Authors: Sastry D. L. , Rama Rao K. V. S. 
Published: July 2007

AbstractThe ClO3 radical observed in γ‐irradiated Ba(ClO4)2 · 3 H2O is studied by ESR and optical absorption techniques. The radical orientation and stability with increased irradiation and thermal and UV light bleaching are discussed. A temperature variation study by ESR reveals that there is an increase of 13.8% and a decrease of 4% in the chlorine p‐orbital and s‐orbital spin densities, respectively, when the temperature is lowered from 300 to 77 K. A comparison of the results obtained for ClO3 with the other iso‐electronic trioxide radicals shows that the maximum fractional change in the spin densities occurs in the case of ClO3 and that these changes depend on the electronegativity of the central atom.
Electron Transport in a Magnetic Field
Authors: Gerlach E. , Harbecke B. 
Published: July 2007

AbstractLindhard's dielectric function is discussed and displayed for an electron gas in an external magnetic field. Using these results the energy loss method is applied to calculate the dynamical resistivity in the quantum limit assuming scattering by ionized impurities. For a degenerate electron system at T = 0 a finite transverse resistivity is found whereas for a nondegenerate one a divergency is obtained.
The Coherence Description of the Dynamical X‐Ray Diffraction from Randomly Disordered Crystals II. Some Numerical Results
Authors: Holý V. 
Published: July 2007

AbstractThe mutual coherence approach to the problem of the dynamical X‐ray diffraction from crystals with randomly distributed microdefects is applied to crystals with small amorphous regions. The rocking curves of such crystals are computed for various diameters of these regions. It is shown that the differences in the results of this theory and the usual kinematical theory of diffusion scattering are not negligible even in the vicinity of the Bragg maximum of the rocking curve. It is shown that the coherence approach to the X‐ray diffraction can give useful results also in the case of diffraction from randomly disordered crystals.
Conduction Processes in High Acceptor Concentration HgTe
Authors: Lombos B. A. , Averous M. , Fau C. , Calas J. 
Published: July 2007

AbstractThe effects of vacancy induced acceptors in zero gap semiconductors, like in HgTe, are treated by the resonant state theory. First, one scattering center is considered, then multiple scattering is developed in the case of acceptor concentrations up to 1 × 1022 m−3. In this investigation the effects of even higher acceptor concentrations (N ≥ 1 × 1023 m−3) are elucidated. It is shown that in this case the resonant state model is no longer applicable since the randomly distributed impurities result in a fluctuating potential field. Thus the impurity disorder introduces an Anderson type conduction process. This is characterized by a large change in the mobility when the Fermi level goes through the acceptor band. These mobilities, related to the Anderson type conduction mechanisms, are in good agreement with the experimentally determined ones in the case of HgTe. While using the resonant state theory, the predicted mobilities are not in satisfactory agreement with the measured ones in the high acceptor concentration range analyzed in this investigation.
Spectral Point Schemes for Evaluating the Expansion Coefficients of State Densities into Orthogonal Functions
Authors: Pisani C. , Ugliengo P. 
Published: July 2007

AbstractAn expansion technique for calculating densities of states (DOS) of crystalline systems previously presented is here tested by evaluating numerically the expansion coefficients. To this purpose, existing special point schemes for Brillouin zone integrations are critically compared. It is shown that schemes where the sampling points are arranged according to a commensurate net are of unpaired efficiency for cubic systems. Very efficient sets of sampling points are also easily generated owing a closed diophantine technique, which can become competitive when lower‐symmetry crystals are considered. The DOS of one of the d‐bands of tight‐binding cubic systems is chosen to test the quality of the results obtained using Legendre polynomials and trigonometric functions as orthogonal sets. 220 sampling points are used to evaluate 16 expansion coefficients; the reconstructed curves are affected by an average relative error of about 4% over the whole band interval. As few as six expansion terms provide an estimate of the position of the Fermi level with an error within 1% of the band interval.
On the Theory of Nonlinear Cyclotron Resonance
Authors: Kopasov A. P. , Molkov I. N. 
Published: July 2007

AbstractThe generation of the second harmonic (SH) of an electromagnetic wave in a conductor in a constant magnetic field parallel to its surface, is studied under the anomalous skin effect. Absolutely diffuse as well as almost diffuse reflection of electrons by the surface is considered. The last case takes account of the growth in the specularity degree of reflection when the angle of electron incidence is ψ → π/2. It is shown that at almost diffuse reflection, the amplitude of the reflected SH can more highly increase in even resonance ω = l'extr (ω is the wave frequency, Ωextr is the extreme value of cyclotron frequency Ω, l is an integer) than in odd one ω = (l + 1/2) Ωextr, just as observed for bismuth.
EPR of Copper‐Doped (NH4)2C2O4 · H2O Single Crystals
Authors: Korkmaz M. , Korkmaz Ö. , Kospançali S. 
Published: July 2007

AbstractEPR studies are made on Cu2+‐doped ammonium oxalate monohydrate. Two Cu2+ lattice sites, Cu2+ (I) and Cu2+ (II), are identified. These sites exhibit two sets of four hyperfine lines in all directions except some special directions. The g‐factors and the hyperfine splittings are calculated for both Cu2+ ions which enter into the substitutional NH4+ sites in the lattice. The spectra for Cu2+ (I) and Cu2+ (II) lattice sites are found to have intensities in the ratio 1:1 suggesting non preferential occupation of the positions by the Cu2+ ions.
The Dielectric Response of a Charge Density Wave (CDW) Distorted Electron–Phonon System in the Precritical Region I. The Self‐Consistent Method
Authors: Heiner E. 
Published: July 2007

AbstractA self‐consistent method is presented, in order to calculate the precritical behaviour of a quasionedimensional electron–phonon system above the Peierls transition temperatureTp.
Energy of the Exciton–Ionized Donor Complex in Anisotropic Semiconductors
Authors: Stauffer L. , Munschy G. 
Published: July 2007

AbstractFor the problem of the anisotropic exciton–ionized donor complex, the wave function is written as a linear combination of products of distance and angle functions. The unknown distance functions are expanded in terms of given radial basis functions and are determined by means of variational calculations. The presented results concern the energy eigenvalue of the complex as a function of the anisotropy parameters and of the electron to hole effective mass ratio.
Thermoluminescence of NaF:Ca2+ Single Crystals
Authors: Bhan S. 
Published: July 2007

AbstractThermoluminescence (TL) of NaF:Ca2+ single crystals after room‐temperature γ‐ray irradiation exhibits six glow peaks at 75, 114, 128, 160, 240, and 290 °C. The 75 and 240 °C peaks are assigned to hole centres; the 114 and 290 °C peaks are attributed to F and F centres, respectively. Involvement of Ca2+ aggregates is suggested in the origin of the 160 °C peak. The origin of the 128 °C peak is explained by assuming the presence of di‐interstitials. It is inferred that F centres are created, even prior to optical bleaching of F centres, to some extent during γ‐ray irradiation. It is also found that on re‐irradiation of the samples containing F centres, these F centres are destroyed. TL spectra show two bands at 420 to 450 and 580 nm. Photoluminescence spectra also show two bands at 450 and 580 nm.
Fourth‐Order Elastic Constant, C1111, of Cubic Crystals
Authors: Prasad O. H. , Suryanarayana M. 
Published: July 2007

AbstractA method for the evaluation of C1111, the fourth‐order elastic constant of the octahedral class of cubic crystals is being suggested which does not involve measurements on crystals using uniaxial stress. Values of C1111 of twenty six cubic crystals are evaluated at room temperature and also at some lower temperatures in seven cubic crystals, namely NaCl, KCl, RbCl, RbBr, RbI, Ge, and Si.
Radiative Decay of Surface Collective Excitations in Polarizable Cylinders
Authors: Burmistrova O. P. , Kosobukin V. A. 
Published: July 2007

AbstractThe dispersion relation and the quantized electrostatic potential are considered for surface collective excitations (SCE, i.e. plasmons and optical phonons) in circular cylinders with frequency dispersion. The operator of potential is used to calculate the matrix elements for the interaction Hamiltonians describing light emission by SCE decaying and also the processes of inelastic scattering of photons and electrons by SCE. The cross sections are derived for the processes of the first and second order relative to the above interaction Hamiltonians, resulting in the emission of a photon at the SCE frequency.
Ionic Thermal Currents under Uniaxial Stress A New Method to Determine Electric and Elastic Dipole Properties
Authors: Siu Li M. , De Souza M. , Kapphan S. E. 
Published: July 2007

AbstractThe method of thermally stimulated depolarization (ITC) is expanded to allow the determination of elastic dipole properties. During sample polarization by the electric field a uniaxial stress is applied simultaneously (mostly parallel to it for practical reasons). Depending on the shape of the elastic dipole associated with the reorienting electric dipole, the total polarization will be either enhanced or reduced by the elastic dipoles being turned either parallel or perpendicular to the stress direction. The change of polarization (i.e. integrated ITC signal) for stress applied in several crystalline directions, yields additional information about the equilibrium orientation and stress splitting coefficients of the dipoles. This novel procedure is tested with a dipolar system known to exhibit a well defined ITC peak at about 25 K, off‐center Ag+ in RbI. The results for the first time reveal clearly the elongated ellipsoidal (cigar‐shaped) form of the elastic distortion around this dipolar center. The question of equilibrium orientation, however, must remain open since both, a <111> and a restricted <110> (90° transitions only) off‐center model, suggested in recent elasto‐optic work by Lüty et al., allow a good fit of the available experimental data.
Transition Temperature for Effective Field Ising Systems
Authors: Silva P. R. , Sábarreto F. C. 
Published: July 2007

AbstractStarting from Callen's exact relation for the Ising Model the transition temperature of different lattices is calculated within an effective‐field‐type treatment. The method treats the spins of the same cluster on different footing. The results for the transition temperature are shown to be better than other effective‐field calculations.
On the Theory of Acoustic Properties of Many‐Domain Ferromagnets
Authors: Mitsek A. I. , Sirota D. I. , Kolmakova N. P. 
Published: July 2007

AbstractThe interaction of a sound wave and a movable domain structure which appears near orientational phase transitions of the first‐order type is considered. The viscous friction is taken into account. The wavelength is considered as being comparable with the domain structure period. The spectrum of magnetoelastic oscillations is calculated, it has a zone character. The evolution of the spectrum branches is investigated when the natural frequency of the domain wall oscillations changes. The attenuation and reflection of sound waves caused by the redistribution of energy between the direct and reverse waves are studied.
Calculation Model for Valence Electrons and Hydrogen Concentration in a‐Si:H
Authors: Ance C. , Ferraton J. P. , Berger J. M. , de Chelle F. 
Published: July 2007

AbstractA simple model is developped to relate the valence electron number to the dispersion energy Ed and the static dielectric constant ϵ(0). This model is applied to hydrogenated amorphous silicon films prepared by glow discharge decomposition of silane. It is shown that the variation of valence electron number and anion valency explain the variation of the dispersion energy. This model allows to determine the hydrogen concentration in a‐Si:H films from two spectroscopic parameters Ed and ϵ(0).
Investigations of the Photovoltaic Tensor in Doped LiNbO3
Authors: Festl H. G. , Hertel P. , Krätzig E. , von Baltz R. 
Published: July 2007

AbstractThe photovoltaic current density in crystals without a center of symmetry depends bilinearly on the components of the light polarization vector via a third‐rank tensor. For LiNbO3:Fe and LiNbO3: Cu the tensor properties are confirmed and three of the four non‐vanishing components determined. The dependence on impurity concentration and on photon energy is also investigated.
Specific Heat Anomaly Connected with a High‐Spin–Low‐Spin Transition in Metallic MnAs1−xPx Crystals
Authors: Krokoszinski H.‐J. , Santandrea C. , Gmelin E. , Bärner K. 
Published: July 2007

AbstractPeaks in the specific heat of ≦ 4 R are observed in metallic conducting MnAs1–xPx crystals with 0.03 ≦ x ≦ 0.13 above the magnetic ordering temperatures and are attributed to high‐spin–low‐spin transitions. This suggests a strong local character for the spin moments and would contradict spin‐polarized extended d‐electron states.
A Proof of Aspherical Valence Charge Parts in the Rock‐Salt Structure Compounds by Means of an X‐ray Bond Charge Model
Authors: Pietsch U. 
Published: July 2007

AbstractThe aspherical valence charge parts are deduced for the rock‐salt structure compounds NaF and MgO by means of a bond charge (BC) model. The valence charge density is described by spherical atoms and an additional particle near the anions in the 〈100〉 directions. The BC amount is smaller according to the dielectric theory, but the other parmeters as position and extension follow its tendency. The anharmonic core vibrations of atoms, the asphericity of the bond charge and its dynamical properties are essential for the zincblende to rock‐salt phase transition.
Influence of Resonance Tunneling on Resistivity in Semiconductors With Ionized Impurities and on Tunneling Current Between Superconductors
Authors: Takács S. , Janetka I. 
Published: July 2007

AbstractThe general results for tunneling of electrons through the system barrier—well—barrier (double barrier, DB) are used to show the importance of resonance tunneling in semiconductors and superconductors. The transmission time for electrons through the double barrier, as well as the transition time between “free” states of the incoming particle and the “bound” states of the well are calculated for determining the trapping probability of electrons by ionized impurities in semiconductors. It is shown that the temperature and electric field dependence of this trapping probability has maxima, which lead to negative resistance effects due to changing the conduction electron concentration. The tunneling current between two superconductors separated by double Schottky barrier (DSB) is derived in the WKB approximation and its dependence on the applied voltage is numerically calculated for a Pb—CdS—Pb system at various temperatures. It is shown that sharp changes of the tunneling current can be detected not only at V = 2Δ (Δ energy gap of the superconductor) but also at higher voltages due to the resonance tunneling effect. These “steps” can be used for very precise measuring the temperature or magnetic field dependence of the energy gap, as well as of some parameters of the Schottky barrier.
Lattice Vibrations of Alkaline‐Earth Hydride‐Fluoride Mixed Crystals Determined from Infrared Spectroscopy
Authors: Vergnat‐Grandjean D. , Vergnat P. , Brice J.‐F. 
Published: July 2007

AbstractSolid solutions of composition MF2–xHx (M = Ca, Sr, Ba) crystallize in CaF2‐type cubic symmetry. The infrared spectra (100 to 4000 cm−1) give informations about the distribution of the H− ions in tetrahedral sites and confirm the character of mixed crystals with a two‐optical‐mode behaviour: the H− ion localized vibration and the fundamental TO mode. Studies of the absorption spectra as a function of x show MF2 clusters with a low H− concentration — the mean value of which is evaluated — and therefore the existence of cubic MH2 clusters — the transverse optical mode of which is determined.
Electron—Phonon Interaction in Disordered Transition Metal Alloys
Authors: Wysokiński K. I. , Kuzemsky A. L. 
Published: July 2007

AbstractThe Hamiltonian of the electron‐phonon interaction is derived and applied to the description of disordered transition metal alloys. The coupled set of equations for the electron and phonon Green functions is derived with the help of the equation‐of‐motion technique. Neglecting the vertex corrections in the self‐energy operators the closed self‐consistent system of equations is obtained. The relevant configurational averaging is performed in the framework of the CPA. The electronic specific heat in the low‐temperature limit is calculated.
Faraday Effect in III— VI Layer Compounds
Authors: Gavaleshko N. P. , Lyakhovich A. N. , Vatamanyuk P. P. , Savchuk A. I. 
Published: July 2007

AbstractThe Faraday effect is investigated in fields up to 20 T and at temperatures from 77 to 300 K applied to the layer semiconductors GaS, GaSe, and InSe. As an example applicable to the InSe crystals, it is shown possible to separate the direct and indirect forbidden transitions both contributing to the Faraday rotation (FR). The oscillatory nature of the FR spectrum at lower temperatures is proved to be due to the exciton contribution. This is the original report about the FR observed in the depth of the fundamental absorption of InSe crystals. The linearity of the FR in the magnetic field is shown to hold for all the compounds under consideration up to 20 T. The observed data are analyzed in order to estimate some band and exciton parameters of the III—VI semiconductors.
On the Theory of Conductivity of Disordered Semiconductors
Authors: Bonch‐Bruevich V. L. , Nguyet To Thi Bich 
Published: July 2007

AbstractThe temperature dependences of the conductivity and mobility of delocalized carriers is calculated in terms of the critical indices describing the behaviour of the energy‐dependent conductivity. Results suggest a possibility to obtain both the indices and the minimum metallic conductivity (if any) from mobility measurements.
Spectrum of the F‐Center
Authors: Katriel J. , Bar‐Adon R. 
Published: July 2007

AbstractA simple one‐electron model, sufficient to account for the main deviations of the spectrum of the F‐center in alkali halides from that of H, is studied. Qualitative features of the spectrum, such as the non‐existence of a 2sσg and 3dσg crossing, are stressed.
Investigation of Transport Coefficients in Semimetals by the Variational Method III. Commutational Effect of Magnetothermo‐E.M.F. in Bismuth
Authors: Gitsu D. V. , Golban I. M. , Kantser V. G. 
Published: July 2007

AbstractThe possibility of the commutational effect (CE) of thermo‐e.m.f. at different orientations of the magnetic field and temperature gradient is investigated in the frames of the variational method of calculation of transport coefficients. It is found that for some of the components of the magnetothermo‐e.m.f. tensor CE appears only in strong and intermediate fields. The importance of strict orientation of sample relative to external affects for the measurement of CE of magnetothermo‐e.m.f. is pointed out.