bluuebunny/crossref_metadata_2025_split huggingface dataset:
Frequency conversion of electromagnetic radiation in polar semiconductors
Authors: Belyantsev A. M. , Kozlov V. A. , Trifonov B. A. 
Published: July 2007

AbstractThe non‐parabolicity contribution of the conduction band and the hot electron effect to the non‐linear susceptibility of n‐type InSb at T = 77 °K are compared using the displaced Maxwell distribution function. Electron scattering on the optical phonons and impurities are taken into account. It is shown that at high frequencies the non‐linear susceptibility is due to the non‐parabolicity of the conduction band.
Electronic specific heat of heavily doped semiconductors in a weak magnetic field
Authors: van Cong H. , Mesnard G. 
Published: July 2007

AbstractThe electronic specific heat at low temperature, in a weak magnetic field, is calculated from a simplified model of heavily doped semiconductors. The treatment is based on the Green function methods applied to disordered systems developed in a previous paper. Two important cases concerning the relation between the carrier and the donor concentration are discussed.
Morse function description of anharmonicity in pressure‐volume relations of cubic metals
Authors: Milstein F. 
Published: July 2007

AbstractThe Morse function, Φ(r) = D(e − 2e), is often used to represent interatomic interactions in investigations of a wide variety of physical phenomena. In view of the wide‐spread use of this function, it is of interest to investigate quantitatively the extent to which experimentally determined anharmonic behavior is exhibited by solids with Morse function interatomic interactions. Numerical values of the Morse parameters D, α, and r0 are determined for a number of cubic metals from experimental values of the lattice constant and the elastic moduli C11 and C12. Morse parameters are then used to compute theoretical pressure‐volume (P‐V) behavior, and comparisons are made with P‐V data determined from shock‐wave measurements. Prior studies by other authors have indicated that the Morse function representation of anharmonic effects in metals is satisfactory; however, the present study shows that this representation, in general, becomes fairly poor for pressures which are large enough to produce considerable non‐linearity in the experimentally determined P‐V behavior.
Analysis of the two‐rand hall effect and magnetoresistance
Authors: Kwan C. C. Y. , Basinski J. , Woolley J. C. 
Published: July 2007

AbstractThe variation of the values of Hall coefficient R and resistance ϱ as a function of magnetic field B is analysed for the case of an n‐type semiconductor with electrons in two different sets of conduction band minima. It is shown that both ϱ0/Δϱ and R0/ΔR should be linear functions of B−2 and that the parameters of the separate bands can be determined from the slope and intercept values of such graphs. The appropriate choice of experimental parameters to ensure the required accuracy of band parameters is discussed.
Microscopic theory of lattice dynamics for ionic crystals II. The contribution of long‐range three‐centre potentials to the phonon dispersion of alkali halides
Authors: Zeyher R. 
Published: July 2007

AbstractThe Heitler‐London expression for the cohesive energy of an ionic crystal contains long‐range three‐centre potentials in the S2‐approximation. Their contribution to the dynamical matrix is examined in terms of q‐dependent charge tensors and numerically calculated for six alkali halides, using self‐consistent free‐ion wave functions and a special multipole expansion. Especially numerical values are given for the three‐centre contribution to the elastic constants and for the longitudinal and transversal effective charges at q = 0. The parameters of a simple shell model are fitted to macroscopic data with and without the inclusion of the three‐centre terms. The corresponding phonon frequencies are compared. It turns out that the usual simple shell model is able to simulate the three‐centre contribution to a large extent by a suitable choice of the parameters. Therefore it is found that an explicit treatment of the three‐centre terms in the phenomenological models doesn't lead to a remarkable improvement.
Energy band structure of semiconductors with the space group D
Authors: Morgan D. J. 
Published: July 2007

AbstractThe energy band structure of semiconductors with the space group Dis investigated using as a starting point results of pseudopotential calculations of the energy band structures of GaAs and Gap. The changes in the energy bands which take place when one goes from the zineblende to the chalcopyrite structure are illustrated, and the arrangement of valence and conduction band states near κ = (0, 0, 0) in the first Brillouin zone of the chalcopyrite structure is discussed. The results indicate that the top two valence bends of a semiconductor with the chalcopyrite structure cross. This suggests that for a particular photon energy the absorption coefficients for radiation polarised parallel and perpendicular to the tetragonal axis might become equal in value.
Acceptor states in tellurium
Authors: Marx R. , Nimtz G. 
Published: July 2007

AbstractRecently acceptor levels due to chemical impurities in tellurium were calculated. Here we present experimental results of the Hall coefficient measured in low magnetic fields between 1.4 and 77 K. The acceptor concentration of the investigated crystals was 1015 cm−3. The observed dependence of the Hall coefficient on temperature can be explained, assuming two acceptor levels above the valence band. This is in agreement with the data predicted by theory.
Excitonic absorption coefficient in semiconductors
Authors: Glinskt R. G. , Song K. S. , Woolley J. C. 
Published: July 2007

AbstractA criticism of Elliott's model of the excitonic absorption coefficient has been made in a recent paper by Auvergne and Camassel. They proposed a model in which the electron‐hole interaction is neglected for the continuum states. This criticism was based mainly on an alleged discontinuity in the exciton envelope function between the discrete and continuum spectra. In the present paper it is shown that in fact, no such discontinuity exists and the electron‐hole interaction should not be ignored in the continuum. Elliott's model is correct within the specified limitations and, appropriately broadened, gives quite satisfactory agreement with the experimental data.
Infrared impurity absorption in n‐type silicon carbide
Authors: Dubrovskii G. B. , Radovanova E. I. 
Published: July 2007

AbstractThe light absorption in the range 2 to 65 μm has been measured in 6H, 15R, and 27R SiC polytypes at 80 and 300 °K. It is shown that at 80 °K there is a broad absorption band in the infrared spectra of each polytype which is associated with electron transitions from the donor level to the conduction band. From the energy position of these bands values of the activation energy were estimated as follows: ΔE = 0.1 eV (6H SiC), ΔE = 0.05eV (27R SiC), and ΔE = 0.04 eV (15R SiC). From the analysis of the fine structure of the absorption in GH SiC at liquid nitrogen temperature three ground levels of the donor impurity in 6H SiC were obtained: two nearly coinciding with the activation energy of about 0.1 eV and one with the activation energy 0.15 eV.
Ionic conductance of silver sulphide and diffusion mechanism of silver ions in α‐Ag2S
Authors: Bartkowicz I. , Mrowec S. 
Published: July 2007

AbstractCationic conductance of silver sulphide has been measured in the temperature range 200 to 440 °C, using silver iodide as an electron blockade. Making use of these measurements the self‐diffusion coefficients of silver in α‐Ag2S have been calculated. Comparison of these data with the results of radio‐isotopic studies reported by Allen and Moore and application of the correlation theory have shown that diffusion of silver in α‐Ag2S proceeds according to the collinear interstitial mechanism.
Determination of optical interband transitions in crystalline quartz from X‐ray spectroscopical data
Authors: Klein G. , Chun H.‐U. 
Published: July 2007

AbstractFor the interpretation of the imaginary part ε2(ω) of the dielectric constant of a solid usually determined from the optical spectra, one can successfully use X‐ray emission spectra and the near‐edge region of X‐ray absorption spectra. This is shown in the case of crystalline quartz. From the X‐ray spectra of this substance conclusions are drawn about the density of states in the valence and conduction band. The possible vertical interband transitions resulting from these conclusions agree very well with maxima in the transition strength ε2(ω) ω2 determined from optical measurements. Furthermore it is demonstrated that the sharp peak at 10.4 eV must be due to an exciton transition in agreement with conclusions drawn from the optical spectra.
Lattice dynamics of highly polarizable homopolar crystals with diamond structure
Authors: Kress W. 
Published: July 2007

AbstractA modified shell model taking into account the isotropic deformation of the charge density is presented. In contrast to the usual 11‐parameters shell model which has to be fitted to inelastic neutron scattering data, the modified shell model needs only six parameters, five of which are related in a unique way to the macroscopic data (elastic constants, Raman frequency, dielectric constant) and the sixth may be obtained from the infrared absorption data. Therefore the modified model is mainly independent from the inelastic neutron scattering results and its parameters are related in a physical way to the macroscopic constants.
The optical constants of CsI in the excitonic region
Authors: Lamatsch H. , Rossel J. , Saurer E. 
Published: July 2007

AbstractMeasurements of the optical constants n(λ) and k(λ) of CsI in the excitonic region are reported. The reflection and the intrinsic luminescence excitation spectra are calculated for bulk crystal and thin crystalline films and compared to the measured spectra.
Localized electrons and their interaction with the local modes in the electrical conduction in metals
Authors: Dubey S. K. 
Published: July 2007

AbstractIn a previous paper the problem of the non‐magnetic impurities in metals has been discussed and the deviations from the Matthiessen relation have been calculated. However, the effect of localized modes was not considered there. In the present paper a more general theory which includes the effect of local modes has been presented. The problem of the localization of the electrons has also been discussed.
Electron spin resonance in As‐doped Ge in a wide range of impurity concentration
Authors: Gershenzon E. M. , Pevin N. M. , Fogelson M. S. 
Published: July 2007

AbstractElectron spin resonance of As donors in Ge has been investigated in the impurity concentration range 1.5 × 1015 to 2 × 1019 cm−3 at temperatures from 1.7 to 4.2 °K. Impurity conduction in the same samples has been studied for NAs ≦ 2 × 1017 cm−3. It is shown that the line‐narrowing in the concentration range 2 × 1017 cm−3 ≧ NAs ≧ 4 × 1016 cm−3 with H0 ∥ [100] orientation cannot be due to the electron motion over impurity centres. Exchange‐narrowing due to the formation of clusters has been discussed. The reduction of angular dependence of the linewidth ΔH with increasing temperature is ascribed to transitions into excited states, by which contributions from different valleys to g‐factor are averaged. For highly doped samples the rate of intervalley transitions has been estimated from the data on angular dependence of ΔH.
Optical properties of amorphous III–V compounds. I. Experiment
Authors: Stuke J. , Zimmerer G. 
Published: July 2007

AbstractFrom reflectivity measurements ε1 and ε2, the real and imaginary part of the dielectric constant, of the amorphous III‐V compounds InSb, InAs, InP, GaSb, GaAs, and GaP are determined in the fundamental absorption region up to 12 eV. Compared with the corresponding curves of the crystals, the spectra of the disordered materials are smeared out and shifted to lower energy. This shift leads to an increase of ε1(0). In the energy region of the E2‐peaks a selective decrease of ε2 is observed. The results for ε2 are briefly discussed in terms of structural properties, and a modified Penn model is applied to the spectral dependence of ε2.
Optical properties of amorphous III–V compounds. II. Theory
Authors: Kramer B. , Maschke K. , Thomas P. 
Published: July 2007

AbstractTwo methods have been used to calculate the ε2‐spectra of amorphous IV‐IV and III‐V semiconductors: The “Complex‐band structure” (CBS‐)method and the “non‐direct transition” (NDT‐)method including energy dependent matrix elements. Both methods start with the calculation of the electronic properties of the corresponding crystals. Results for amorphous Ge, Si, GaP, GaAs, GaSb, InP, InAs, and InSb are compared with experimental ε2‐spectra.
Zur Kinematik von Disklinationen
Authors: Günther H. 
Published: July 2007

AbstractDie nichtlineare Statik der Disklinationen wurde unter Verwendung eines vierdimensionalen Formalismus zur nichtlinearen Kinematik verallgemeinert. Die Disklinationsströme können dabei in weitgehender Analogie zu den Versetzungsströmen eingeführt werden. Es zeigt sich, daß eine Bewegung von Disklinationen i. a. mit der Erzeugung bzw. Vernichtung von Versetzungen verbunden ist, was einen wesentlichen Einfluß auf die realen Bewegungsmöglichkeiten von Disklinationen haben wird.
Neutron diffraction study of the magnetic structure of Mn3B4
Authors: Neov S. , Legrand E. 
Published: July 2007

AbstractFrom the neutron diffraction measurements it is concluded that below the Néel temsperature of 392 K the intermetallic compound Mn3B4 becomes antiferromagnetic. At this stage only the Mn(2c) atoms are magnetic. Below 226 K the Mn(4g) atoms also become magnetically ordered and deform the collinear antiferromagnetic structure to a spiral structure, with an angle of 157.5°, which at lower temperature gradually develops to a collinear antiferromagnetic structure again. The saturated magnetic moments are 2.92 μB for the Mn(2c) atoms and 0.44 μB for the Mn(4g) atoms.
Magnetic properties of NiCr alloys
Authors: Besnus M. J. , Gottehrer Y. , Munschy G. 
Published: July 2007

AbstractNew magnetization measurements on NiCr alloys are reported. At increasing Cr concentrations c less than 11 at%, the mean atomic moment M0 = 0 for c = 12 at% Cr. In the critical concentration range, 11 < c < 15 at% Cr, the experimental data are analysed in terms of the itinerant band model of very weak ferromagnetism. Several characteristic properties related to the effective exchange interaction and to the band structure near the Fermi level are deduced from this analysis.
Optical spin orientation of non‐equilibrium electrons in GaAs and GaAsAlAs solid solution
Authors: Dzhioev R. I. , Fleisher V. G. , Kanskaya L. M. , Ninu O. A. , Zakharchenya B. P. 
Published: July 2007

AbstractThe results of optical orientation investigation of electron spins in semiconductors excited by circularly polarized light are reported. The occurrence of orientation is due to the presence of spin‐orbit splitting of the valence band. The effect has been investigated by measuring the degree q of circular polarization of the recombination radiation and has been observed in GaAs crystals and the solid solution GaAsAIAs. The dependencies of q on the wavelength of the exciting light have been obtained at 77 and 4.2° K. It has been found that in the case of GaAs crystal E increases and on the contrary, decreases in the solid solution, with temperature decreasing from 77 to 4.2 °K. Depolarization of radiation in an outer magnetic field has been investigated and the lifetimes T of nonequilibrium carriers and the times of spin relaxation τs, are determined. For the GaAs crystal τ (77 °K) = (1.4 ± 0.2) × × 10−10 s and τs (77 °K) = (2.8 ± 0.6) × 10−10 s is found. These values increase with decreasing temperature and at 4.2 °K become equal to (2.4 ± 0.3) × 10−10 s and (8.0 ± 1.5) × × 10−10 s, respectively. In the case of GaAs‐AIAs t and T, have been found with an accuracy determined by the magnitude of the g‐factor.
The electrical properties of the single crystal spinel CoAl2O4
Authors: Matveeva N. G. , Shelykh A. I. 
Published: July 2007

AbstractThe electrical conductivity over the range of 300 to 1300 °C and the thermoelectric force (700 to 1300 °C) have been measured on monocrystalline samples of cobalt aluminate. Calculations were made for the drift mobility; the values of the mobility are shown to be low (10−2 to 10−4 cm2/Vs). The drift mobility increases exponentially with temperature with an activation energy Ea = 0.8 eV. A satisfactory description of transport phenomena in CoAl2O4 can be obtained in terms of the small polaron model.
Energy levels and spectroscopic parameters of some Nd3+ complexes deduced from their solid state diffuse reflectance
Authors: Tandon S. P. , Govil R. C. , Surana S. S. L. 
Published: July 2007

AbstractThe values of Slater‐Condon (F2, F4, F6) and Racah (El, E2, E3) interelectronic repulsion and Landé (ζ4f) parameters and electronic energy levels have been computed from the diffuse reflectance spectra of eight Nd3+ complexes. Configuration interaction parameters (α β, Y(22, 1) and Y(22, 3)) have also been computed for the Nd3+ aquo‐ion. The decrease in the F2 values of the complexes as compared to the free ion is greatest among all the parameters. The bonding parameter b1/2 has been computed from the observed nephelauxetic ratio. The relative variation of covalent bonding in the complexes has been discussed, the effects of the crystalline hosts on the Fk and ζ4f parameters have also been examined.
Magnetic properties of face‐centered cubic Fe65(PtxIr1 − x)35 alloys
Authors: Shiga M. , Kosaka M. , Nakamura Y. 
Published: July 2007

AbstractThe magnetic properties of the disordered Fe65,(PtxIr1 − x)35 alloys with f.c.c. structure were investigated. The alloys are ferromagnetic over a composition range of x > 0.7; the average magnetic moment decreases rapidly with decreasing x deviating from the Slater‐Pauling curve and the Curie temperature also decreases with decreasing r. The alloys show antiferromagnetic behaviour for x < 0.7; the temperature independent susceptibility of Fe65Ir35 alloy implies an absence of localized moments and an addition of platinum causes a strong temperature dependent susceptibility suggesting a formation of localized moments. The magnetic properties of the present alloys are discussed on the base of assumptions on the character of 3d electrons at iron sites.
Tenfold d‐electron degeneracy in the Hubbard model and transition‐metal magnetism I. The paramagnetic‐ferromagnetic transition
Authors: Siegel E. J. , Kemeny G. 
Published: July 2007

AbstractReplacing the simplified s‐electron picture of Penn [a] [4], intrasite d–d interactions are included in the Hubbard model. Choosing k‐space correlation functions to represent the paramagnetic and ferromagnetic states, the tenfold degenerate eigenvalue problem is solved and free energies are calculated self‐consistently for various combinations of the three parameters: bandfilling, direct interaction constant divided by the bandwidth, exchange interaction constant divided by the bandwidth. The paramagnetic‐ferromagnetic phase boundary surface is plotted at near zero and finite temperatures with the third dimension being exchange interaction constant divided by the bandwidth. The near‐zero‐temperature trend shows that the inclusion of exchange, as expected, enhances the ferromagnetic region at the expense of the paramagnetic region. This is exactly opposite to the nondegenerate, t‐matrix result of Caron and Kemeny [6]. Finite temperature calculations show the same trend with increasing exchange, but shift the phase boundary surface so as to decrease the ferromagnetic region.
Excitation of the Cs‐5p core level in cesium halides at 30 K
Authors: Saile V. , Skibowski M. 
Published: July 2007

AbstractThe excitation of the Cs‐5p core level in Cs halides which starts a t about 13 eV was studied by measuring the reflection spectra of evaporated films between 12.5 and 26 eV at room temperature and a t 30 K. Synchrotron radiation was used as a light source. In comparison to the spectra at room temperature new remarkable fine structure was found at 30 K. The very complex spectra are discussed with regard to band calculations including excitons associated with critical points. I n a complementary view the spectra are compared with transitions of the free Cs+ ion. A sideband at the high energy part of the most prominent exciton was observed for every Cs halide. It is, presumably, caused by excitonphonon interaction.
Jahn‐Teller Effect on Transition Metal Ions in Silver Halides III. Interpretation
Authors: Ulrici W. 
Published: July 2007

AbstractThe temperature dependence of the optical absorptions involving orbital dublets (Eg) split by dynamic Jahn‐Teller effect (JTE) (measured on AgCl and AgBr doped with Ti3+, Fe2+, and Cr2+) is discussed. From the results obtained for excited Eg states the linear JT‐coupling parameters and the frequencies of the JT‐active ϵGg mode are derived. These ϵg modes are found to be localized around the impurity ion. It is shown that the small and temperature independent oscillator strength of the transition between the JT‐splitting levels of the Eg ground state (measured on Cr2+) is a consequence of the action of the dynamic JTE. The weak increase of the JT‐splitting ΔE of the Eg ground state with increasing temperature is caused by the temperature dependence of the frequency of the ϵg mode following from the thermal expansion of the crystal.
The Effect of Phonon Heating on Photoelectric Phenomena (II)
Authors: Abakumov V. N. , Schleifstein M. , Yassievich I. N. 
Published: July 2007

AbstractThe effect of phonon nonequilibrium on photoelectric and photomagnetic phenomena is considered in such semiconductor samples, in which phonon energy relaxation is controlled by irradiation into the surrounding medium. The phonon distribution function is calculated in such a sample for the case, that phonon flow and minimum sample dimension are in one direction. A table of formulae determining photoconductivity Δσ and photomagnetoelectric e.m.f. VPM in several physically realizable situations is given.
Molecular Field Theory and Phase Transitions in Partially Finite Spin Systems
Authors: Angelescu N. , Costache G. , Nenciu G. 
Published: July 2007

AbstractA molecular field model of an homogeneous thin film with free surfaces is studied. The existence of one and only one phase transition, which is of second order, is proved. A study is made of the distribution of magnetization across the film thickness. In the limit of in‐ finite number of layers, a description of the bulk is obtained, which is equivalent to the Weiss molecular field description. The critical temperature of the film approaches the bulk critical temperature as the inverse square of the number of layers.
The Photogradient E.M.F. of Hot Carriers
Authors: Ašmontas S. , Požela J. , Repšas K. 
Published: July 2007

AbstractResults are presented of the investigation of the hot carriers' photogradient e.m.f., Ufg dependent on the electric field intensity in n‐ and p‐type germanium and n‐type silicon. The rate of change of the photogradient e.m.f. in n‐Ge is found to decrease with an increase of the electric field intensity at fields higher than 5 kV/cm. This is explained by the influence of the higher 〈100〉 minima on heating of electrons. The measurements were carried out at room temperature by a microwave technique. The dependence of Ufg on the electric field intensity is calculated in the electron and hole temperature approximation.