bluuebunny/crossref_metadata_2025_split huggingface dataset:
All Effective Mass Approximation for Several Bands
Authors: Lukes T. , Roberts M. 
Published: July 2007

AbstractThe effective mass formalism is generalized to include the effect of several bands by constructing an approximate Green's function for the periodic lattice. Energy levels are obtained for a hydrogenic impurity in a periodic lattice described by two and three parabolic bands. In addition to the energy levels predicted by effective mass theory a deep level is found. An explicit expression for the deep level is given in terms of the band parameters and a comparison with the experimentally observed deep levels in gallium arsenide is made.
Propriétés galvanomagnétiques des alliages bismuth‐étain à 4°K et à faible champ magnétique
Authors: Malgrange J. L. 
Published: July 2007

AbstractLes propriétés galvanomagnétiques des alliages bismuth‐étain ont été mesurées à 4,2°K pour des dopages allant de 8×1017 à 5×1019 cm−3. On déduit des expériences le nombre de porteurs dans chaque bande, et leurs mobilités. Les résultats obtenus sont interprétés dans divers modèles de bande. On met ainsi en évidence la forme non parabolique de la principale bande de valence. On observe une augmentation des mobilités des porteurs légers près des limites des bandes. Ce résultat s'interprète comme résultant de la diffusion sur des impuretés ionisées écrantées par plusieurs types de porteurs de densités d'états très differentes. La comparaison des mobilités dans les bandes centrées aux points L de la zone de Brillouin met en évidence la similitude de ces bandes.
Diffraction by H.C.P. Crystals with Extrinsic Faults — The Solution by Difference Equations
Authors: Holloway H. 
Published: July 2007

AbstractDiffraction by h.c.p. crystals with randomly arranged extrinsic faults is analysed using the difference equation method. The results confirm the random‐walk calculation by Lele et al. An earlier difference‐equation calculation is shown to be in error.
Phase Relations, Crystal Structures, and Magnetic Properties of Erbium—Iron Compounds
Authors: Buschow K. H. J. , van der Goot A. S. 
Published: July 2007

AbstractThe phase relations, crystal structures, and magnetic properties of intermetallic compounds occurring in the Er–Fe system have been investigated. A phase diagram is given. The lattice constants of the compounds ErFe2, ErFe3, Er6Fe23, and Er2Fe17 have been determined. These compounds are ferrimagnetic with the Fe moments coupled antiparallel to the Er moments. Their Curie temperatures decrease with increasing Fe concentration. The compounds ErFe2, ErFe3, and Er6Fe23 have been observed to show a compensation point.
Time‐Dependent Ginzburg‐Landau Equation for Superconducting Alloys in High Magnetic Fields
Authors: Weller W. 
Published: July 2007

AbstractA superconductor containing nonmagnetic impurities is considered in the limit of small mean free path (l ≪ ξ0) and high magnetic field (H ≈ Hc 2). With the help of the method developed by Gorkov and Eliashberg the time‐dependent Ginzburg‐Landau equation and the differential equation for the vertex part are derived from the microscopic theory. The resulting Ginzburg‐Landau equation is appreciably simplified in the cases, in which the vertex part reduces to the scalar electromagnetic potential. It is shown that this simplification is possible for the case of slow motion of the lattice of the vortex lines (flux‐flow) caused by a static electric field.
Collision Integrals for Displaced Maxwellian Distribution
Authors: Bløtekjær K. , Lunde E. B. 
Published: July 2007

AbstractThe rate by which particles, momentum, and kinetic energy are transferred in collisions is considered for charge carriers with displaced Maxwellian velocity distributions. The collision integrals are expanded in power series of the average momentum and exact expressions are obtained for the general term of the series. The following scattering processes are considered: deformation potential and piezoelectric coupling to acoustical phonons, polar and nonpolar coupling to optical phonons, intervalley scattering, equivalent valley scattering, ionized impurity scattering, and electron‐hole scattering. Exact analytic summation of the series is possible for some processes. It is shown that, to second order in the average momentum, the loss of particles and energy (but not momentum) depends only on the average kinetic energy of the carriers, and not on how the energy is distributed among thermal and drift energy.
Radiative Recombination in Highly Doped Germanium
Authors: Benoit à la Guillaume C. , Cernogora J. 
Published: July 2007

AbstractUsing optical injection the recombination radiation in germanium doped up to 3.2 × 1019 cm−3 with arsenic has been studied at low temperatures (4, 14, and 77 °K). Several spectra have been reported previously. The purpose of this paper is to explain: a) the extent to which the momentum conservation is ensured by the impurities; b) the shape and position of the spectra at least qualitatively for the highly doped samples by taking into account the density of states tail of the holes.
ESR Spectra of Gd3+‐Doped SrMoO4 and CaWO4 in External Electric Field
Authors: Nepsha V. I. , Sherstkov Yu. A. , Legkikh N. V. , Meilman M. L. 
Published: July 2007

AbstractLinear splitting of ESR signals of Gd3+ ions introduced into SrMoO4 and CaWO4 lattices were observed under applied electric field. Measured signal shifts can be described quite accurately in terms of a correction which is added to the spin Hamiltonian and at most includes only quadratic terms of spin projection operators. It has been found that the constant Re (R), characteristic of the signal shifts of Gd3+ impurity ions, is somewhat greater for SrMoO4 than for CaWO4. The experimental results can be explained consistently only by assuming that the local symmetry of the neighbourhood of Gd3+ ions in SrMoO4 and CaWO4 is represented by the S4‐group. By way of a specific example it is shown that the study of ESR spectra in an externally applied electric field gives a wide opportunity for establishment and more exact definition of a symmetry group of the local neighbourhoods for impurity ions in crystals.
Conduction in Strongly Compensated p‐Type GaSb
Authors: D'olne Campos M. , Gouskov L. , van Mau A. Nguyen 
Published: July 2007

AbstractHall coefficient and resistivity of strongly compensated p‐type GaSb are measured between 10 and 300 °K. The results are interpreted in the high temperature range by free hole transport in the valence band. In the low temperature range hopping charge transfer between impurity centres is supposed to account for conduction.
The Preparation of Graded‐Band‐Gap Single Crystals of II–VI Compounds
Authors: Reimers P. 
Published: July 2007

AbstractGraded‐band‐gap single crystals of ZnxCd1−xSe, CdS1−xSex, CdSe1−xSx, Zn1−xCdxS, and ZnxCd1−xSySe1−y with x and y increasing along the direction of growth have been prepared by two different vapor phase methods. Typical crystal dimensions in the systems CdS1−xSex and CdSe1−xSx are 6 × 7 × 20 mm3, in the other systems 2 × 3 × 8 mm3. The gradient of the band gap in the system CdS1−xSex could be varied between 0.1 and 2.0 eV/cm. The change in band gap vs. crystal position was determined by absorption measurements. All crystals show edge emission at liquid air temperature under excitation by uv light.
The Coercivity of Hard Ferrite Single Crystals
Authors: Jahn L. , Müller H. G. 
Published: July 2007

AbstractMagnetic properties of Sr‐, Ba‐ and Sr‐Ba‐ferrite single crystals are reported. From torque measurements results: Sr‐ferrite: Ms = (380 ± 20) G, K1 = (3.5 ± 0.1) × 106 erg cm−3; Ba‐ferrite: Ms = (380 ± 20) G, K1 = (3.2 ± 0.1) × 106 erg cm−3. A large difference was found by a comparison of Hci, theor (coherent rotation) with Hci, meas (oriented Sr‐ferrite magnet). The very small (generally even positive) nucleation fields, measured on single crystal plates of different chemical composition and different crystal sizes can qualitatively explain the low values and the grain size dependence of Hci.
Transverse Elementary Excitations of the System of Interacting Crystal Electrons
Authors: Stolz H. 
Published: July 2007

AbstractFrom many‐body theory the dielectric tensor is calculated for a system of crystal electrons under the assumption of a statically screened interaction. For an insulator with cubic symmetry the result is inserted into the dispersion equation defining the transverse elementary excitations. The discrete roots of this equation are shown to correspond to excitons and, under certain conditions, to collective excitations which may be characterized as “transverse plasmons”. Since the transverse elementary excitations determine the surface impedance and thus the optical properties of the system, one should expect the transverse plasmons to be observable in optical investigations. In the framework of the systematic many‐particle approach the notions of bare excitons, true transverse and longitudinal excitons, and polaritons are discussed.
Electrical Properties of Monocrystalline Uranium Diphosphide
Authors: Henkie Z. , Trzebiatowski W. 
Published: July 2007

AbstractElectric resistivity (2 to 600 °K), thermoelectric power (100 to 700 °K), and Hall effect (290 to 450 °K) were determined for single crystals and polycrystalline samples of UP2. This compound possesses tetragonal structure and exhibits a strong anisotropy of the transport properties. At room temperature the resistivity along the c‐axis is about three times larger than in the perpendicular direction (≈ 700 and 205 μΩ cm, respectively), while the thermoelectric power is two times lower along the c‐axis (≈ +20and +37.8μV/°K). The ordinary Hall coefficient with negative sign is equal to ‐3 × 10−12 V cm/A Oe, the carrier concentration is 2 × 1022 cm−3 and the estimated Fermi energy is about 3.2 eV. The phenomenological interpretation of the obtained data is based on a model with a conduction band resulting from the overlap of 7 s and 6d bands while the 5f electrons yield a narrow band of lower energy lying apart from the conduction band.
Observation of Dislocations in Tellurium by Transmission Electron Microscopy
Authors: Doukhan J. C. , Doukhan N. , Saada G. , Thomas B. 
Published: July 2007

AbstractA method of thinning tellurium single crystals by chemical polishing has been developed for the study of dislocations by transmission electron microscopy. The preliminary results concerning the identification of the glide planes and the Burgers vectors of dislocations in this material are described together with some comments on the contrast phenomena resulting from the high elastic anisotropy of tellurium.
Physico‐Chemical Properties of 1,3,5,7‐Tetranitro‐1,3,5,7‐Tetrazacyclooctane (HMX)
Authors: Maycock J. N. , Verneker V. R. Pai , Lochte W. 
Published: July 2007

AbstractThe electronic absorption spectrum of β‐HMX has been measured and discussed in terms of two processes, 1. an intramolecular excitation of the group and 2. possible exciton structure. The photochemical decomposition of α‐, β‐, and γ‐polymorphic forms of HMX has been investigated and shown to be a one photon process with an associated thermal process whose energy depends on the energy of photon excitation. Irradiation with 2537 Å light produces a coloring of the crystals. A tentative model for the photo‐decomposition of HMX into formaldehyde and nitrous oxide is discussed. ‐ Radiation (2537 Å) effects on the α‐, β‐, and γ‐polymorphs of HMX have been investigated by a simultaneous DTA‐TGA technique. Shifts in both exotherms and endotherms have been found with the effects being proportional to the polymorph densities, i.e. β > α > γ for the phase change endotherms and β < α < γ for the main decomposition exotherm. A possible explanation based on the different conformational structures has been proposed for the sequential radiation damage.
The Shape Parameter of Donor Band Tails in Gallium Arsenide
Authors: Wittmann H. R. 
Published: July 2007

AbstractThe shape parameter of the donor band tail in heavily n‐doped GaAs and in GaAs p‐n junctions has been obtained from absorption and electroluminescence measurements. The experimentally determined dependence of the shape parameter on donor concentration follows a power law as predicted by Kane.
Galvano‐Thermo Magnetic Transport Coefficients in n‐InSb at Low Temperatures
Authors: Sodha M. S. , Dubey P. K. , Sharma S. K. 
Published: July 2007

AbstractGTMTC have been calculated in n‐InSb using Kane's model and the ionized impurity scattering at low temperatures (20 to 90 °K). The theoretical results have been compared with the corresponding experimental data; it is seen that the theoretical results agree satisfactorily with the experimental values at low magnetic fields.
The Green's Function Method and the Many‐Band Model in the Study of a Short‐Range Perturbation
Authors: Goossens P. , Phariseau P. 
Published: July 2007

AbstractThe convergence of the Green's function method is tested on a simple linear model, for which the exact position of the extra energy states is known. It is found that this computation technique gives very accurate results, under the condition that in the sums over the energy bands a sufficient number of terms is considered. On the other hand, the numerical data agree with the recently published critical studies on the energy band problem. The approximative results in the one‐band model appear to be very unsatisfactory. Furthermore, the position of the extra energy levels is essentially determined by the bands lying nearest to the examined state.
Pressure Dependence of the Elastic Constants for Silver from 77 to 300 °K
Authors: Ho P. S. , Poirier J. P. , Ruoff A. L. 
Published: July 2007

AbstractThe pressure derivatives of the isothermal elastic constants for Ag have been measured from 77 to 300 °K, which were found, within the accuracy of the experiment, to be almost independent of temperature. Cook's self‐consistent method, as described by Ho and Ruoff, was applied in analysing the ultrasonic data. The high‐ and low‐temperature limits of the Grüneisen constants, γH and γL, calculated from our results are compared with γt calculated from thermal properties. In the temperature range studied, γt is found to be close to γt. However, at 0 °K, γt is in good agreement with γL. The compression data of several static and shock‐wave experiments have been re‐analyzed according to the Murnaghan equation of state. The bulk modulus and its pressure derivative so obtained agree well with the values measured by ultrasonic methods.
Radiation Defects Created by Co60 γ‐Rays in p‐ and n‐Type Si of High Purity
Authors: Konozenko I. D. , Semenyuk A. K. , Khivrich V. I. 
Published: July 2007

AbstractRadiation defects created by γ‐irradiation of Co60 at 300 °K in high purity p‐Si (ϱ = 5 × 103 to 4 × 104 Ω cm) and n‐Si (ϱ = 440 to 5 × 103 Ω cm) are investigated by measurements of Hall effect and minority carrier lifetime. The oxygen concentrations in Si are in the range of 5 × 1014 to 5 × 1015 cm−3; compensation of electrically active impurities is low. It is shown that defects in high purity Si created at 300 °K are divacancies and complexes of vacancies with donor or acceptor impurities. Divacancies introduced by γ‐irradiation are not the primary defects. They become predominant after “exhaustion” of the dopant. When divacancies become the predominant defects the Fermi level occupies its limit position Ev + 0.390 eV in the gap. At low doses (Φ < 1016 photons/cm2 vacancy‐impurity complexes and at heavy doses (Φ > 1017 photons/cm2 divacancies play the main role in the recombination process.
Diffusion of Impurities in Semiconducting Substitutional Solid Solutions InAs1−ηPη and GaAs1−nPη
Authors: Arseni K. A. , Boltaks B. I. , Dzhafarov T. D. 
Published: July 2007

AbstractA break was found in the dependence of the diffusion coefficient of zinc on the composition of GaAs1−ηPη at a phosphorus content in the solid solution η ≈ 0.4. The same break is observed in the dependence of the Fermi level on the composition of GaAs1−ηPη. The experimental data obtained agree with the theory. The diffusion of zinc in inhomogeneous solid solutions of GaAs1−ηPη (gradual heretojunctions) was found to increase which can be attributed to the effect of an internal electric field produced by a gradient in the hetero‐junction energy gap width as well as to a coordinate dependence of the zinc diffusion coefficient.
The Edge Emission and Phonon Effects in the Photoluminescence of CdTe
Authors: Panossian J. R. , Gippius A. A. , Vavilov V. S. 
Published: July 2007

AbstractIn the photoluminescence spectra of CdTe four series of lines can be resolved in the temperature range 4.2 to 78 °K; each of them is due to the electron transitions involving LO phonons (I. II. III, IV). The relative intensities of these series (the zero‐phonon lines at 1.528; 1.539; 1.548; and 1.556 eV at 20°K) depend on the sample temperature and the present impurities. The series I and II are similar in their intensity dependence on temperature to the so‐called LT (low temperature, long wavelength) and HT (high temperature, short wavelength) series of the green edge emission of CdS. Series I is dominant in crystals doped with shallow donors; this fact in connection with the temperature dependence and the dependence of the line shape on the excitation intensity leads to the conclusion that it is due to radiative transitions between shallow donors (ED = 0.015eV) and acceptors (EA = 0.0067 eV). The temperature dependence of the intensity of series II and the lines' shape suggest that this series is due to radiative transitions of electrons from the conductivity band to acceptor levels (EA = 0.0067 eV). The variation of the relative intensities of series I and II with the type and content of impurities in the samples correlates with the variation of the relative intensities of the lines in the 1.59 eV region ascribed to the exciton annihilation at donors and acceptors. The distribution of phonon replica intensities in series I and II corresponds to the expression In = I0Nn/n!(n = 0,1,2,…). The changes of the parameter N observed in some cases are due to the overlapping of series I and II with the series III or IV. the nature of which is not quite clear. The variation of the parameter N (which depends on the intensity of the electron‐phonon interaction) with the level depth is found to agree qualitatively with the theory of Hopfield. The band at 0.50 eV corresponding to the transitions involving deeper levels shows a structure which may be due to the interaction of electron transitions with local phonons having an energy of 0.045 eV.
The Interaction of Intersecting Flexible Dislocations in the Presence of Friction Forces in the Lattice. (The Case for Repelling Dislocations)
Authors: Predvoditelev A. A. , Bushueva G. V. , Bulygina T. I. , Vodzinskaya N. 
Published: July 2007

AbstractThe interaction of flexible repelling dislocations and their passage through one another is considered. It is shown that the process of dislocation interaction may be broken into two parts: a) gradual bending accompanied by the increase of the energy of the dislocation configuration; b) loss of stability; here the dislocation system undergoes a transition from the quasi‐static to the dynamic state. Dislocation intersection takes place under dynamic conditions. The analysis was performed for two cases: infinite crystal and thin plate. There is a certain difference in the dislocation shapes in both cases. The theoretical calculations are found to be in agreement with experimental data.
On the Mechanical Properties of Crystals with Covalent Bond
Authors: Gridneva I. V. , Milman Yu. V. , Trefilov V. I. 
Published: July 2007

AbstractThe parameter α = H/kTm characterizes the resistance of a crystal lattice to dislocation motion. For crystals with a covalent component of the interatomic bond the parameter α increases with the degree of the interatomic bond orientation. At high temperatures α determines the value of the critical shear stress and the temperature t* at which a sharp change of the temperature dependence of the critical shear stress begins. It is shown that t* = \documentclass{article}\pagestyle{empty}\begin{document}$\sqrt {\alpha /} \sqrt {3\,c} $\end{document}, where c characterizes the slope of the curve τcr = f(T) at the temperature t*. Passage of the temperature t* is accompanied by a change in the mechanism of plastic deformation. The correlation of strength and plastic properties with the degree of the interatomic bond orientation is discussed.
Non‐Adiabatic Transitions in Crystals
Authors: Osherov V. I. , Medvedev E. S. 
Published: July 2007

AbstractThe problem of non‐adiabatic transition within an impurity centre is considered in the presence of dynamic diffusion of the vibrational wave‐packet. Using the term‐interaction constant as expansion parameter limits are found for the applicability of perturbation theory depending on the dispersion of the vibrations.
Dislocation Structure and Macroscopic Characteristics of Plastic Deformation at Creep of Silicon Crystals
Authors: Myshlyaev M. M. , Nikitenko V. I. , Nesterenko V. I. 
Published: July 2007

AbstractIt has been proved that the creep curve of silicon crystals under uniaxial compression at 2 to 15 kp/mm2 and 900 to 1300 °C consists of five characteristic portions, each of them exhibiting a typical dislocation structure. The stationary stage is characterized by misoriented subgrains. The stationary creep rate at stresses up to 10 kp/mm2 is governed by the kinetic equation

and controlled by barriers associated with dislocations in the subboundaries.
Magnetic Susceptibility and Energy Band Structure of Zirconium Monocarbide
Authors: Borukhovich A. S. , Dubrovskaya L. B. , Matveenko I. I. , Geld P. V. 
Published: July 2007

AbstractThe magnetic susceptibility of zirconium monocarbide has been studied as a function of temperature and concentration in the homogeneity region 0.58 ≦ x ≦ 1.0 and at temperatures from 20 to 1300 °K. It is shown that the temperature dependence χ(T) of all the samples may be described by the equations

The obtained results are discussed in terms of concepts available on the electronic structure of the cubic carbides of the group IVa and Va transition metals. A “flat” minimum was found in the curve N(E) lying near stoichiometric composition of the monocarbides.
Magnetic Moment Measurements on Caesium and Rubidium Manganese Chloride
Authors: Hoel L. A. 
Published: July 2007

AbstractCs2MnCl4 · 2 H2O and Rb2MnCl4 · 2 H2O are two antiferromagnetic substances with a similar triclinic structure, but with different Néel temperatures of 1.84 and 2.24°K respectively. The magnetic moments have been measured at 0.5 °K in external fields up to 70 kOe. In order to calculate the exchange and anisotropy fields the measurements were made on single crystals which were oriented with the ordering direction first parallel and then perpendicular to the field. The alignment axis is the O‐Mn‐O direction.
X‐Ray Determination of the Debye Temperature of Uranium Monocarbide
Authors: Colella R. , Dragone D. , Merlini A. 
Published: July 2007

AbstractBragg reflections by single crystals of UC, cleaved along (100) planes, were found to have negligible extinction for values of sin ϑ/λ in the range from 0.4 to 1.2 Å−1. The integrated intensities of these reflections were measured by using MoKα radiation at various temperatures from 77 to 773 °K. Plots of the logarithm of the integrated intensities vs. temperature, or vs. (sin ϑ/λ)2 at a fixed temperature, were straight lines. The slopes of the plotted lines yielded an average value θM = (265 ± 5). °K for the Debye temperature defined in terms of the uranium atoms only, and θM = (366 ± 7) °K, using the average of the U and C masses in the Debye‐Waller factor. These values are compared with those determined by different experimental techniques.