bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Capacity and Quasi‐Chain Dynamics of Diamond‐Like Structures
Authors: Tarassov V. V. , Demidenko A. F.
Published: July 2007

The heat capacities of a number of semiconducting substances (Si, GaAs, GaP, etc.) have been calculated on the basis of the quasi‐chain dynamics of covalent crystals [9]. It is shown that the characteristic frequencies v3 and v1 correspond to the respective dispersion frequencies at the points Γ(0, 0, 0), X(1, 0, 0), and L(0.5, 0.5, 0.5) of the Brillouin zone determined from the inelastic scattering of slow neutrons, and that it is possible to calculate the parameters ϑ1 and ϑ3 from the data of multi‐phonon absorption. The heat capacities of GaP, measured in the range 55 to 300°K, are given.
Determination of the Average Number of Replacement Collisions in an Electron‐Irradiated F.C.C. Crystal (Ni3Mn)
Authors: Becker D. , Dworschak F. , Lehmann C. , Rie K. T. , Schuster H. , Wollenberger H. , Wurm J.
Published: July 2007

The electrical resistivity and saturation magnetization damage rates in ordered Ni3Mn and in pure Ni have been measured during 1.0 and 3.0 MeV electron irradiation at low temperatures. The effect of Frenkel pairs on the damage rates is assumed to be equal in Ni and in Ni3Mn; thus, the difference between the damage rates merely yields the disordering effect caused by replacement collisions. Changes of the long range order parameter S then were determined using empirical expressions relating the electrical resistivity and the saturation magnetization to S. Consideration of the relationship between S and the number of replacement collisions in 〈110〉 rows yields an average number of (2.2 ± 2.2) replacements per Frenkel pair. This result is discussed in view of experimental recombination volumes and computer experiments.
Impurity Diffusion in Face‐Centred Cubic Metals
Authors: Naik M. C. , Anand M. S. , Paul A. R. , Agarwala R. P.
Published: July 2007

An attempt has been made to correlate the Gibbs free energy of the self and impurity diffusion in f.c.c. metals (Ag, Cu, Au, Ni, Pb, and Al) with some of their physical parameters (like atomic radius r, melting temperature T of the solute, and compressibilities k′ and k of the solute and the solvent) along with the electrostatic interaction (βZ) of the solute and the solvent. A linear relationship of the form ΔG = A + B (Tr/(k′ + 2k)) − βZ could be obtained with constants A and B, characteristic of each of the solvents.
Formation of Radiation Defects by Channeling Particles
Authors: Kumakhov M. A.
Published: July 2007

The problem of interaction of channeling ions with chain nuclei forming the channel is considered. Born‐Mayer potentials for CuCu, Moliere, Firsov, and Lindhard potentials are considered as interaction potentials. The energy transferred to the chain nuclei is estimated. In some cases this energy may exceed the threshold energy of atomic displacement. The light channeling ions do not produce displacements. The problem of the influence of the channeling effect on the radiation cascade is also considered. It is shown that this influence is insignificant except for the cases when the initially displaced atoms have high energies.
Peculiarities of the Energy Spectrum and Edge Absorption in the Chain Compounds AVBVICVII
Authors: Chepur D. V. , Bercha D. M. , Turyanitsa I. D. , Slivka V. Yu.
Published: July 2007

Some band structure peculiarities of AVBVICVII compounds have been investigated by methods of group theory, the interaction between the chains being taken into account. Experiments show that the peculiarities occur on both spectra of the crystals BiSeI, the absorption edge and the photoconductivity. The results obtained are explained by band structure peculiarities.
ESR Studies of Cupric Ion in Various Oxide Glasses
Authors: Imagawa H.
Published: July 2007

ESR spectra of cupric ions in borate, silicate, and phosphate glasses were analyzed by the LCAO MO method of Maki and McGarvey. The covalency of the B2g π‐orbital was found to change with the bond strength of the network‐former. Particularly it reflected clearly the weakening of BO bonds in alkali borate glasses with increasing alkali content or with increasing ratio of BO4 tetrahedra to BO3 triangles. Microscopic fluctuations in glass were found essential to explain the line shape of the hyperfine structure. Two different states of cupric ions were observed in some quenched glasses.
Shell Model Treatment of the Vibrations of Crystals Containing Substitutional Defects. II. On the Theory of Defect‐Induced One‐Phonon Absorption
Authors: Strauch D.
Published: July 2007

A formalism for defect‐induced one‐phonon absorption in the harmonic approximation is presented. The influence of charge changes of defects on the crystal dipole moment is twofold: the charges themselves as well as their displacements are perturbed by these changes. Averaging over defect configurations energy shift and width of plane‐wave‐like phonons is obtained. A self‐consistent solution of the perturbed Green's function which takes into account perturbations up to second order in the defect concentration is used. In the homopolar crystals absorption occurs only if the actual (not effective) charges are changed. Comments are made on effective charges and their changes.
A Contribution to the Calculation of Magnetization Curves and Minor Loops
Authors: Heinecke U.
Published: July 2007

The model of an anisotropic permanent magnet is imitated on a digital computer and the demagnetization curve and the family of minor loops are calculated. The approximations of this method are: rectangular loops of the elementary magnets and the location of these particles at lattice points. The values of the magnetic interaction field intensity are evaluated from experimentally determined parameters of a real magnet sample. The calculated loops agree in most of the characteristics with the experimental curves. Deviations may be reduced by a suitable correction of the distribution curve of the critical field values of the particles.
Transport Properties of Silver Telluride in the Solid and Liquid States
Authors: van Dong Nguyen , Tung Pham Ngu
Published: July 2007

Measurements of the electrical resistivity, Hall coefficient, and thermoelectric power have been carried out for silver telluride over a large temperature range including both solid and liquid states. The analysis of the experimental data shows that in the solid state the transport properties are governed by an ambipolar process with an electron mobility much higher than the hole mobility (μn = 10 μp). It is found that the temperatur dependence of the electron mobility can be represented by a T−3‐law. Deviations from the stoichimetric composition of Ag2Te have been studied. For all specimens, melting is accompanied by discontinuous variations in the transport propeties. Above the melting point, the magnitude of the measured parameters and their temperature dependence show that liquid silver telluride behaves as a semiconductor. The contribution of Ag+ ions to transport phenomena is suggested to account for the behaviour of the electrical properties. Experimental data have been analysed in terms of conventional theories.
Observation of Quantum Galvanomagnetic Phenomena in n‐Type Indium Antimonide
Authors: Huff H. R. , Kawaji S. , Gatos H. C.
Published: July 2007

Quantization effects in the bulk galvanomagnetic properties of n‐type InSb were studied in conjucntion with the transport properties of compound semiconductor surfaces. The transverse and longitudinal magneto‐resistivity were measured at 4.2, 50, and 77°K. The former was found to increase with increasing magnetic field at all temperatures and (for a given temperature) was an order of magnitude larger than the latter which became saturated at the two higher temperatures. At 4.2°K, the electrons were weakly degenerate and the bulk mobility was determined by ionized impurity scattering. At 77°K, the electrons were non‐degenerate and the predominant scattering mechanism was probably high‐temperature optical phonon scattering.
Die Berücksichtigung der Austauschwechselwirkung im Zweiteilchenbild der Exzitonen und ihr Einfluß auf die Exzitonenspektren
Authors: Dos K. , Haug A. , Rohner P.
Published: July 2007

Die Berücksichtigung der Austauschwechselwirkung der Electronen liefert einen zusätzlichen Term in der Zweiteilchengleichung für Exzitonen, der zu einer wesentlichen Modifizierung der Exzitonenspektren führt. Dadurch können sowohl die Nullfeldaufspaltung der Exzitonenlinien als auch Abweichungen von der Wasserstoffähnlichkeit der Spektren gedeutet werden.
The Ordering of Ni3V
Authors: Tanner L. E.
Published: July 2007

Stoichiometric Ni3V undergoes a cubic → tetragonal ordering transition (Al → DO22) by means of nucleation and growth. Electron diffraction microscopy and other experimental techniques reveal that the reaction is continuous, proceedind in three stages: I. Nucleation of coherent particles of the ordered phase in clusters of common orientation; II. Growth of these clustered nuclei to impingement forming isolated cells of unique orientation ‐ each cell is subdivided into anti‐phase domains; III. Growth of the cells to consume the remaining disordered phase, producing a mosaic substructure of mutually orthogonal cells, or “transformation twins”. Severe internal strains develop during the sequence, and secondary structural changes, such as twinning and recrystallization, effect their relief.
X‐Ray Spectra and Electronic Structure of Elements at the End of the First Long Period from 29Cu to 34Se
Authors: Nemoshkalenko V. V. , Mindlina M. A. , Mamko B. P.
Published: July 2007

The form of the Kβ2,5‐bands of the elements Ni and Zn is shown to have a fine structure not previously observed. The comparison of the K‐, L‐, and M‐spectra of metallic Ni, Cu, Zn, and Ge demonstrates the localization of the localization of the 3d bands. In Ni the d‐symmetry states form a narrow sub‐band at the Fermi level, in Cu these states are shifted to lower energies, and the process continues with increasing atomic number of the element. The shape of the Kβ2,5‐band of Ni, Cu, and Zn is due to the overlap of the Kβ5‐ and Kβ2‐bands and represents mainly the distribution of p‐symmetry states in the outer energy band of these elements. The formation of the 4s‐level in Ge is discussed. It is concluded that p–d transitions must take place in CuNi alloys in the outer shell of the outer shell of the Ni atom.
Hopping Electrical Conduction and Thermal Breakdown in Natural and Synthetic Mica
Authors: Davidson A. T. , Yoffe A. D.
Published: July 2007

The electrical properties of thin mica crystals have been measured between 4 and 520°K, and have been related to optical absorption measurements and to electron microscope observations. The dc conductivity and breakdown strength depends on the concentration of iron and titanium in the mica. It is suggested that impurities act as localized centres for electrical conduction in mica and that the Poole‐Frenkel model applies at high temperatures while electrons tunnel between the centres at low temperatures. The conductivity of mica depends on the frequency of the applied field. Two types of breakdown have been found. The results are interpreted as avalanche breakdown in synthetic micas and thermal breakdown in natural micas.
Experimental Evidence for Interband Mixing in Rare‐Earth Intermetallic Compounds
Authors: de Wijn H. W. , Buschow K. H. J. , van Diepen A. M.
Published: July 2007

Measurements of the Knight shifts and susceptibilities of rare‐earth intermetallic compounds have been extended to YCu, GdCu, TbCu, DyCu, HoCu, and ErCu. The phenomenological exchange constants 𝒥sf between 4f‐electron spins and conduction‐electron spins are derived to be −0.21 eV. Also the paramagnetic Curie temperatures of the compounds GdCu1−xGax have been measured. The Knight shifts and Curie temperatures are discussed in terms of the Ruderman‐Kittel‐Kasuya‐Yosida theory. For the various series of rare‐earth intermetallic compounds the s‐f exchange integral Γ = 2 J(0) and the Fermi wave vector kF have been determined. Γ is found to be a continuous function of kF, with a sign reversal at kF ≈ 1.4 Å−1. This observed behavior is consistent with the calculations of Watson, Koide, Peter, and Freeman on the effect of interband mixing on the exchange interactions.
Plasma Oscillations in Semiconductors with Non‐Standard Dispersion Law in the Presence of Electric and Magnetic Fields
Authors: Almasov L. A. , Dykman I. M.
Published: July 2007

The effect of the magnetic field H on the frequency of plasma oscillations in semiconductors with non‐standard energy band structure is investigated. In such semiconductors in the presence of a constant electric field F a specific bandstructural mechanism of amplification or attenuation of the oscillations arises. Assuming isotropic energy band structure of Kane type, this mechanism leads to attenuation. The magnetic field H ⟂ F decreases the attenuation, while the oscillations polarized in a certain way can even amplify it. Assuming a weakly anisotropic band structure, like that of the holes in Ge, the magnetic field affects the oscillations of light and heavy holes in different way. In this case also polarization directions are possible at which the bandstructural amplification of oscillation occurs in the magnetic field.
Green Function Theory of Transport Properties of Anharmonic Metals
Authors: Kishore R.
Published: July 2007

General expressions for the electron and phonon energy shift and widths are derived with the help of the double time temperature dependent Green's function by using a Hamiltonian which includes both anharmonicity and electron‐phonon interaction. The expression for the phonon width shows that Green's function technique provides an understanding of Matthiessen's rule. Well known temperature dependence of the electron and the phonon relaxation times is reproduced by a simple calculation of the electron and the phonon widths at low and high temperature limits. It is found that the effect of anharmonicity on the electronic transport properties of metals is negligible. Its effect on the lattice transport properties is predominant at high temperature and at low temperature the effect of electron‐phonon interaction is predominant.
Spin‐Wave Theory of the Anisotropic Ferromagnetic
Authors: Mitsek A. I. , Kolmakova N. P. , Skryabin Yu. N.
Published: July 2007

Using the method of successive approximations, the spin‐wave theory of the anisotropic ferromagnetic is constructed in the Heisenberg model. The influence of the magnetic anisotropy on the specific heat, the temperature dependence of the spontaneous magnetization and the paramagnetic susceptibility as well as the temperature dependence of the magnetic anisotropy constant K1 is calculated. The difference in the temperature dependences of the “single‐ion” anisotropy and “anisotropic exchange” is discussed. It is shown that when K1 is small enough, the frequency of the ferromagnetic resonance (FMR) depends on T in the same way, as in the thermodynamic theory of FMR. The line‐width of FMR ΔH is determined by 3‐magnon processes and depends weakly on temperature. The processes of the transformation of a quantum of uniform precession into two spin waves of different polarizations gives the main contribution to ΔH. The contribution of 2‐magnon processes of the scattering on the impurity atoms is calculated as well.
Atomistische Behandlung von Kinke und Sprung einer Stufenversetzung in NaCl. II. Der abrupte Sprung
Authors: Eisenblätter J.
Published: July 2007

Nach denselben Methoden wie in Teil I dieser Arbeit [1] werden Energien der zwei niedrigsten abrupten Sprünge und Energien der Dissoziation eines vollen in zwei Halbsprünge berechnet.
OH− Dissociation and U2 Decomposition in Hydroxide‐Doped KCl and KBr Crystals
Authors: Kurz G.
Published: July 2007

We report quantitative results concerning the dissociation of OH−, supporting the conception given first by Kerkhoff. U2 centres created by this reaction are thermally stable below about 100°K. It is shown that U2 centres can be destroyed by optical bleaching. At 4.5°K, U and H centres are created simultaneously; this is described as

We suggest for the underlying mechanism that the first process after U2 excitation is a noncubic relaxation of the lattice (static Jahn‐Teller effect) followed by a 〈110〉 replacement sequence as described by Williams to form a H‐centre–vacancy pair, the vacancy finally being occupied by the H− ion. – In KCl a reverse reaction can be induced either by thermal activation or by bleaching with H light. – Oscillator strengths of the U2, H, and OH− bands are calculated from the results using the Smakula equation.
De Haas ‐ Van Alphen and Shubnikov ‐ De Haas Effect in n‐HgSe in Strong Magnetic Fields
Authors: Bliek L. M. , Landwehr G.
Published: July 2007

The De Haas ‐ Van Alphen and the Shubnikov ‐ De Haas effect are measured on oriented samples of single‐crystalline HgSe with electron concentrations between 1.08 and 3.26 × 1018 cm−3 in pulsed magnetic fields up to 210 kOe. The results in strong fields show that the beating of the oscillations observed at smaller fields is due to inversion asymmetry splitting rather than to anisotropy of the Fermi surface. A pronounced spin splitting of about 1/4 of a period is observed, allowing the evaluation of the Landé factor of the conduction electrons.
Anisotropy of the Electric Conductivity of Tellurium Single Crystals
Authors: Rothkirch L. , Link R. , Sauer W. , Manglus F.
Published: July 2007

The quantity σ⟂/σ∥ of tellurium single crystals is measured in the temperature range 80 to 550°K. The results may be understood under following assumptions: The relaxation time for the scattering of holes by acoustic phonons is nearly isotropic; the relaxation time for the scattering of holes by dislocations is characterized by the relation 〈τp⟂〉 < 〈τp∥〉; the anisotropy of the effective hole mass mp∥/mp⟂ is markedly temperature‐dependent; the highest valence band edge and the lowest conduction band edge show approximately the same anisotropy between 200 and 550°K.
The Effect of the Local Mode Self‐Energy in the U‐Center Sidebands
Authors: Zeyher R. , Bilz H.
Published: July 2007

The theory of the sideband absorption of the U‐center is reformulated. The contribution of the anharmonic self‐energy of the local mode is taken into account in the resonance denominator and in the sideband absorption itself. The first modification explains some difficulties in describing peak positions and heights arising in the usual perturbation treatment. The second effect is a simple form of final state interaction which leads to an absorption in the gap region of the sideband. Numerical values of the effects are given.
A Study of the Effect of Deformation on the ESR, Luminescence, and Absorption of MgO Single Crystals
Authors: Sibley W. A. , Kolopus J. L. , Mallard W. C.
Published: July 2007

The effect of plastic deformation on the optical absorption, ESR, and thermoluminescent properties of MgO has been investigated. Plastic deformation produces an optical absorption band at about 217 nm whose intensity is proportional to the percent of deformation. No new ESR signals were detected in the deformed crystals. When deformed crystals are irradiated with 60CO γ‐rays, however, the ESR signal from the F‐center is observed and several new optical absorption bands also appear. Impurity ion ESR signals in γ‐irradiated samples have been compared with thermoluminescence spectra. The results indicate that the blue thermoluminescence at 3.3 eV and 85°C is due to Fe2+ converting to Fe3+ and the red thermoluminescence at 1.7 eV and 85°C is due to the formation of Cr3+.
Calculation of the Influence of Bound Divacancies on the Isotope Effect for Self‐Diffusion in F.C.C. Metals
Authors: Bakker H.
Published: July 2007

With the aid of Howard's theory for computing the correlation factor for self‐diffusion by divacancies, the influence of divacancies on the isotope effect for self‐diffusion in f.c.c. metals is calculated. It turns out that a divacancy contribution lowers the isotope effect. This result is compared with experimental values for palladium and silver, and with the usual interpretation of small isotope effects following Vineyard's theory.
Correlation and Orthogonality Corrections to the Cohesive Energy of Metallic Copper
Authors: Brown J. S.
Published: July 2007

Orthogonality and correlation corrections to the cohesive energy of metallic copper are discussed, using a simple model based on the Green function method introduced by Gubanov and Nikulin.
Density Matrix Method in the Theory of Optical Spectra of Impurities in Solids
Authors: Peuker K.
Published: July 2007

The results of a previous paper describing the vibrational structure in the secondary radiation spectrum of impurities in solids are extended to the general case of finite temperature. The impurity centres are treated as two‐level electronic systems interacting with a localized mode of vibration. The anharmonic interaction of the localized mode with the crystal modes is taken into account. Expressions are derived describing the Raman‐type and luminescence parts of the spectrum. The relation between the integral intensities of these spectral components are examined as a function of the frequency of the incident light.
Electron Drift Mobility in KCl
Authors: Hirth H. , Tödheide‐Haupt U.
Published: July 2007

From electron transit time measurements the electron drift mobility in KCl has been deduced for the temperature range 200 to 500 °K. By comparison with low temperature Hall mobility data it is concluded that above 300 °K the measured values coincide with the microscopic mobility μ of conduction band electrons which may be described by μ = μ0[exp (θ/T) − 1]. Below 300 °K the measured drift mobility is controlled by the interaction of the conduction band electrons with shallow traps. These traps also influence the electron lifetime. Since the electron mobilities in AgCl and TlCl deduced from the literature may also be represented by the expression given above that this expression is generally valid for ionic crystals with intermediate electron‐phonon coupling.
Thermal Conductivity of GeS and GeSe
Authors: Okhotin A. S. , Krestovnikov A. N. , Aivazov A. A. , Pushkarskii A. S.
Published: July 2007

The thermal conductivity of the semiconductor compounds GeS and GeSe has been measured in an argon atmosphere in the range from room temperature to 500 °C. The analysis of the data obtained indicates that the heat transfer in these compounds is governed by phonons. The applicability of Keyes' formula to the description of the high‐temperature thermal conductivity of germanium chalcogenides is demonstrated.
The Electronic Polarizabilities of Ions in Alkali Halide Crystals
Authors: Ledovskaya E. M.
Published: July 2007

An expression for the electronic polarizability of ions in ideal alkali halides is obtained. For this purpose a second order correction of the perturbation theory to the energy of the crystal, placed in an external electric field, is used. As a perturbation the interaction of ions in the crystal and the interaction of the crystal with the external macroscopic electric field are taken simultaneously. The additivity rule for the electronic polarizability of the ideal crystal and for the polarization energy of the non‐ideal crystal is confirmed. The difference between the value of the electronic polarizability of the ion in a crystal and that of the free ion is qualitatively correct.
On the Hall Effect in Hopping Transport
Authors: Klinger M. I.
Published: July 2007

The transverse mobility and Hall effect in hopping transport are considered for both non‐adiabatic small polarons and impurity conduction. Appropriate formulas are derived and analyzed for both static and high‐frequency electric fields, and compared with formulas earlier discussed for static fields.
On the Long Period Photoconductivity of Cu2O
Authors: Surnev L.
Published: July 2007

The slow photoconductivity of Cu2O has been studied. The results obtained can be explained by assuming the existence of three types of traps. The first type contains the highest levels in the forbidden gap. They create the fast component (τ ≈ 10−4 s) of the photoconductivity at room temperature. Levels lying 0.7 eV below the bottom of the conduction band correspond to the second type of traps. They cause a reversible slow component at temperatures below 130 °C. The traps associated with the deepest levels (1.35 eV) produce an irreversible slow component of the photoconductivity at temperatures below 120 °C. The close correlation between the photoconductivity components leads to the assumption that all three types of traps are concentrated on definite sites of the sample. For that reason, with the filling up of traps, barriers are formed in the vicinity of these sites. These barriers determine the kinetics and extent of filling of the traps.
On the Angular Variation and Texture Dependence of Young's Modulus in Cold‐Rolled Copper Sheet
Authors: Bunge H. J. , Ebert R. , Günther F.
Published: July 2007

The Young's modulus was measured in different directions in the rolling plane of coldrolled copper sheets with different textures, and also calculated in the Hill approximation from X‐ray data. The agreement was fairly good. A deviation of about 7% with twofold symmetry with respect to the normal direction is possibly due to the form of the grains or the orientation correlation.
Investigation of the Energy Band Structure of GaSb by a Semi‐Empirical Kohn‐Rostoker Method
Authors: Bordure G.
Published: July 2007

The energy band structure of GaSb is investigated by the Kohn‐Rostoker (KR) method. A “muffin‐tin” potential is described and two parameters are introduced for fitting some splittings at points of symmetry of the Brillouin zone with experimental data. Other characteristic splittings are compared with experimental results. The results are also compared with those obtained by other methods.
ENDOR Measurements of Interstitial Hydrogen Atoms in RbCl (U2 Centres)
Authors: Lehnert G. , Spaeth J. M.
Published: July 2007

An ENDOR investigation of U2 centres in RbCl is reported. The superhyperfine and quadrupole constants of two Rb shells and one Cl shell in the surrounding lattice are determined. The experimental results are compared with those obtained in other alkali halides. The measurements are interpreted in terms of a simple U2 centre wave function.
Über die Energie‐ und die Energie‐Winkel‐Verteilung der Anregung von Rumpfelektronen durch Stoß mit schnellen Primärelektronen bei Natrium
Authors: Arendt P.
Published: July 2007

Die in [2] angegebene Anregungsfunktion aus Rumpfbändern beim Stoß mit schnellen Primärelektronen wird am Beispiel des Natriums berechnet. Es ergibt sich, daß die Anregung aus den Rumpfbändern bedeutend weniger anisotrop erfolgt als die Anregung aus dem Leitungsband. Die anhand der berechneten Verteilung mit Hilfe einer Transporttheorie berechnete Sekundärausbeute stimmt im Rahmen der zu erwartenden Genauigkeit mit der experimentellen Ausbeute überein.
Diffraction Contrast from Dauphiné Twin Boundaries in Quartz
Authors: McLaren A. C. , Phakey P. P.
Published: July 2007

Electron diffraction contrast evidence is obtained for the presence of Dauphiné twins in amethyst quartz. A model for the Dauphiné twin boundary which does not involve broken SiO bonds is proposed and shown to be consistent with the contrast features observed with different operating reflection. X‐ray diffraction topography of macroscopic Dauphiné twin boundaries in natural quartz show identical contrast effects and support the electron microscope observations. – It is shown that a different type of fringe pattern, not previously described, can arise at boundaries if the extinction distances in the two parts of the twin differ significantly. Diffraction contrast from such fringe patterns is described and explained using Gevers‐Amelinckx intensity relations.
Electron Microscopic Contrast Effects at the Interface between Two Different Polytypes. II. Interface 2H–4H
Authors: d'Aragona F. Secco , Delavignette P. , Gevers R. , Amelinckx S.
Published: July 2007

The contrast effects associated with the interface between two different polytypes of zinc sulfide, 2H and 4H are discussed. A special type of fringes characterized by a different spacing at the top and bottom end is associated with such interfaces. The fringe patterns associated with overlapping interfaces are discussed as well. The transformation 2H–4H is found to be a shear transformation. The prismatic stacking faults in wurtzite are found to be growth faults; they are eliminated by the passage of transformation partials on the basal plane.
The Nucleation of Stripe Domains in Thin Ferromagnetic Films
Authors: Holz A. , Kronmüller H.
Published: July 2007

A micromagnetic calculation is given of the critical thickness of the nucleation of stripe domains in thin ferromagnetic films with so‐called perpendicular anisotropy. The micromagnetic equations were solved in linear approximation by means of a complete system of functions. The paper presents the critical thickness Dcr and the corresponding wavelength λcr as a function of the ferromagnetic constants. The agreement between our calculations and the measurements of Saito et al. on permalloy is good. For Fe‐films good agreement with the measurements of Bourret and Dautreppe is obtained only for Dcr but not for λcr. The calculated value for λcr is about a factor 1.5 greater than the experimental value.
Recombination Radiation Spectra in ZnSiP2 Crystals
Authors: Alekperova E. E. , Valov Yu. A. , Goryunova N. A. , Ryvkin S. M. , Shpenkov G. P.
Published: July 2007

The recombination radiation spectra of ZnSiP2 single crystals produced by different methods and doped with different impurities have been measured. The recombination radiation was excited by a high‐energy electron beam. The recombination radiation spectra of ZnSiP2 appeared to be similar to that of the wide forbidden band A3B5 phosphides. The recombination takes place at levels located in the forbidden band of this semiconductor. The investigation of the recombination radiation spectra permits us to judge of luminescent properties of ZnSiP2 crystals produced by different techniques and of their energetic spectrum. In some cases it gives a possibility to some extent to characterize the peculiarities of methods of production of this substance.
Spectral Characteristics of the Injection Quantum‐Amplifier
Authors: Oraevskii I. N. , Popov Yu. M. , Strakhovskii G. M.
Published: July 2007

Experimental investigations and a theoretical analysis were made of the spectral characteristics of an injection quantum‐amplifier based on GaAs diodes. The feedback in a Fabry‐Perot cavity was attenuated by using an antireflective coating. For a sample whose characteristics were investigated in detail the threshold current after the coating was 7.8 times higher. That permitted to amplify a signal by a factor 103 without noticeable regeneration. For sufficiently small input signals the gain dependences on frequency and pumping current were measured when the amplifier operated in a linear regime. The results are discussed in terms of energy states (“tails”) formed near the conduction band by the impurities. Possible reasons of the discrepancy between the theoretical and experimental results at high frequencies and high currents are discussed.
Generation of the Exciton‐Impurity Complex by Fast Electrons
Authors: Glauberman A. E. , Pundik A. V. , Kozitskii S. V. , Ruvinskii M. A.
Published: July 2007

The problem of excitation of the exciton‐impurity complex (EIC) by fast electrons in a non‐metallic crystal is considered using a many‐electron approach. The operators which describe singlet and triplet state of EIC are introduced. The expressions for the probability of creation of the EIC are obtained and possible selection rules for corresponding transitions are analysed. A comparison is made with case of generation of free Wannier‐Mott exciton.
Anregungsspektren stationärer Photoströme in Anthrazen‐Kristallen im Bereich der Singulett‐Absorption
Authors: Bauser H. , Ruf H. H.
Published: July 2007

Im Bereich der Singulett‐Absorption verläuft das Photostromspektrum nicht immer im gleichen Sinn wie das Absorptionsspektrum, sondern oft im Gegensinn; ferner tritt ein vorgelagertes Maximum bei 415 bis 430 nm auf. Der Typus des Photostromspektrums wird bestimmt durch die Reinheit der Kristalle, die Injektionsfähigkeit der Anode, die angelegte Spannung und die Bestrahlungsstärke. Der qualitativen Deutung der Meßergebnisse werden Trägererzeugung an der Oberfläche durch Singulettexzitonen und Trägerbefreiung im Inneren durch Triplettexzitonen als konkurrierende Prozesse zugrunde gelegt. — Die Lage des vorgelagerten Maximums läßt sich unter Berücksichtigung der inhomogenen Lichtverteilung im Kristall berechnen. Im Gebiet starker Absorption überwiegt die Trägerbefreiung durch Triplettexzitonen, die durch reabsorbiertes Fluoreszenzlicht erzeugt werden.
Mössbauer Investigation of Ferroelectric Boracites
Authors: Trooster J. M.
Published: July 2007

The Mössbauer spectra of 57Fe in the iron‐boracites Fe3B7O13X with X = Cl, Br, or I, and of 57Fe as an impurity in Ni3B7O13X have been measured at temperatures between 80 and 1100 °K. The results give qualitative information on the vibration amplitude in the different phases, on the crystal field splitting of the Fe2+ ion in the cubic phase, and on the character of the binding of the Fe2+ ion, and have led to the discovery of a trigonal phase in the Fe boracites.
Electrical Resistivity of Noble Metals by Krebs's Method
Authors: Singh A. K. , Sharma P. K.
Published: July 2007

The electrical resistivity of the noble metals copper, silver, and gold as a function of temperature is calculated in the free‐electron approximation using Krebs's model for the lattice dynamics of metals. Bailyn's averaging procedure is used to simplify formidable integrals over the Fermi surface. The calculated values of the resistivity are compared with available experimental data. The general shape of the theoretical and experimental resistivity curve is found to be similar, but the experimental values exceed the theoretical ones.
Cyclotron Masses and Orbital Diameters in Ag Determined by Cyclotron Resonance in a Thin Slab
Authors: Henningsen J. O.
Published: July 2007

The cyclotron mass of neck orbits in Ag has been determined by performing the experiments on a thin slab. This geometry allows one to eliminate the belly orbits. The result mc/m0 = 0.37 ± 0.01 differs from previous cyclotron resonance measurements, but is in agreement with the theory and de Haas‐van Alphen experiments. In addition approximate k‐space diameters have been determined for the central and non‐central [111] belly orbits. In both cases the agreement with theory is good.
Hall Effect in Single Crystals of Magnesium
Authors: Alty J. L. , Stringer J.
Published: July 2007

The Hall effect has been measured in seven single crystals of high purity magnesium at room temperature. The results indicate that the two independent coefficients of the Hall tensor are equal, the metal behaving isotropically; R⊥ = R| = −(7.8 ± 0.8) × 10−11 m3 C−1. The single crystal values of the Hall coefficients for the hexagonal metals Mg, Zn, Cd, and Ti are tabulated; there is no simple relation between them and the axial ratio.
Bulk Quantum Efficiency in Indium Antimonide
Authors: la Guillaume C. Benott À , Fishman G.
Published: July 2007

The bulk quantum efficiency η of indium antimonide is studied between 4 and 300 °K with doping concentrations ranging from 2 × 1014 to 2 × 1018 donors cm−3. Using the formula η = τN/(τN + τR) (where τR is the radiative lifetime and τN the non‐radiative one), it is possible to deduce from the experimental results the importance of different non‐radiative processes since τR is relatively well‐known. It is shown that the Auger effect is predominant with regard to the recombination through the mechanism of trapping (Shockley‐Read process) at high temperatures or for high doping concentrations.
Luminescence de cristaux de tellurure de cadmium
Authors: Noblanmc J. P. , Loudette J. , Duraffourg G.
Published: July 2007

Nous avons étudié la photoluminescence et la cathodoluminescence du CdTe aux températures de l'azote, de l'hydrogène ou de l'hélium liquides entre 1,3 et 1,6 eV avant et après polissage chimique. Les monocristaux étudiés ne sont pas intentionnellement dopés, leur concentration en porteurs est déterminée par la pression partielle de cadmium pendant le recuit. Nous avons observé sur tous les échantillons une raie très large (0,1eV) située autour de 1,42 eV dont l'intensité est très sensible au polissage chimique et varie proportionellement à l'excitation. La comparaison de cette raie avec la raie „intrinsèque”︁ (≈ 1,58 eV à 78 °K), dont l'intensité est proportionnelle au carré de l'excitation, nous permet de conclure qu'elle est due à des défauts situés dans une couche de surface de profondeur inférieure à 1 μm. La raie „intrinsèque”︁ (1.594 et 1,58 eV à l'hydrogène et à l'azote liquide respectivement) présente sur le flanc haute énergie une structure à ces deux températures. L'application du principe de bilan détaillé permet d'obtenir la forme du coefficient d'absorption que nous comparons aux spectres de réflectivité: nous attribuons la raie principale à l'annihilation de l'exciton libre de l'état fondamental n = 1 dont nous évaluons l'énergie à (1,5838 ± 0,0007) eV à 78 °K, et à (1,5855 ± 0,0007) eV à 22 °K. La structure côté haute énergie est attribuée à l'annihilation de l'état n = 2 de l'exciton libre (1,591 eV à 78 °K) et à la transition bande à bande (1,595 eV à 78 °K).
Stage I Recovery of Deformed Platinum
Authors: Swanson M. L. , Quenneville A. F.
Published: July 2007

The stage I recovery (below 60 °K) of deformed 99.999% purity Pt has been investigated by residual electrical resistivity measurements. After extensions of 1 to 3% at 5 °K, recovery peaks were observed at (16 ± 1), (28 ± 1), and (36 ± 1) °K, with associated activation energies (0.05 ± 0.01), (0.073 ± 0.01), and (0.14 ± 0.01) eV. A prior deformation and 300 °K anneal not only increased the stage I recovery by a factor of two, but also enhanced its structure. The 16 °K substage was due to short range defect migration. The 28 °K substage was similar to that observed after electron irradiation of Pt, which is attributed to free interstitial migration. The main Frenkel pair annealing substages which are observed after fast particle irradiation were absent in deformed Pt.
Electron Population of Dislocation Levels in an Illuminated Covalent Semiconductor
Authors: Fortini A.
Published: July 2007

The occupation ratio of the acceptor levels associated with the dangling bonds of a dislocation in a covalent semiconductor submitted to optical electron‐hole generation is calculated thermodynamically. The same approach is also applied to the similar problem, first considered by Read, of an n‐doped semiconductor. Numerical calculations for germanium at different temperatures, assuming a dislocation level 0.2 eV below the conduction band edge, show that the occupation ratio increases as the temperature is decreased. At moderate temperatures, values as high as 0.1 can be reached by reasonable injection or impurity doping, the efficiency of both methods being roughly the same.
Aragonite Transformations Observed in the Electron Microscope
Authors: Burrage B. J. , Pitkethly D. R.
Published: July 2007

It is possible to observe the known transformations of aragonite to calcite to lime using an electron microscope. Aragonite undergoes a sudden and violent transformation when heated by the electron beam. Twins and dislocations disappear, leaving a strained crystal of aragonite of occasionally calcite. Further heating produces calcium oxide with a strongly preferred orientation relative to the carbonate.
Energy Band Structure of AIN
Authors: Hejda B.
Published: July 2007

The energy band structure of AIN is calculated by means of the orthogonalized plane wave method at the points Γ, A, K, H, M, and L of the Brillouin zone. 135 plane waves have been used at the point Γ. The results to Herman and Skillman who calculated them with the Slater approximation for the exchange potential have been used as atomic wave functions and potentials.
Eine MO‐theorie der Spin—Phonon‐Wechselwirkung
Authors: Böttger H.
Published: July 2007

Die Spin—Phonon‐Wechselwirkung eines paramagnetischen Ions in einem Ionenkristall durch den Van Vleck‐Mechanismus wird in einem Modell untersucht, in dem das paramagnetische Ion und seine nächsten Nachbarn als Molekül betrachtet werden, dessen Zustände durch MO (molecular orbital)‐Funktionen beschrieben werden. Es wird ein Elektron‐Phonon‐Wechselwirkungsoperator aufgestellt, der neben Termen des üblichen Punktladungsmodells weitere durch Überlappung und Kovalenz bestimmte Terme enthält. Eine Abschätzung für das System Ni++ in MgO zeigt, daß der Einfluß der einiger dieser Terme auf die Spin—Phonon‐Wechselwirkung vergleichbar mit dem Einfluß der Terme des Punktladungsmodells sein kann.
Lattice Reflection and Optical Constants of ZnSnP2 Crystals with Chalcopyrite and Sphalerite Structure
Authors: Zlatkin L. B. , Markov J. F. , Stekhanov A. I. , Shur M. S.
Published: July 2007

The infra‐red reflectivity of ZnSnP2 has been investigated in the wavelength range 2 to 60μm at T = 295 °K. The optical constants and vibrational frequencies are determined; for the chalcopyrite structure they are ϵ∞ = 8.1 ± 0.2, ϵ0 = 10.0 ± 0.4, n = 2.84 ± 0.04, ωl 0 = 368 cm−1, ωt 0 = 330 cm−1; for the sphalerite structure they are ϵ∞ = 8.3 ± 0.2, ϵ0 = 10.8 ± 0.4, n = 2.88 ± 0.04, ωl 0 = 362 cm−1, ωt 0 = 318 cm−1. The effective ionic charge is estimated by the Szigeti formula. The values are for the chalcopyrite structure e*/e = 0.58, for the sphalerite structure e*/e = 0.63. The compressibility has been estimated to β × 1012 = 1.28 and 1.34 (cgs units) for the chalcopyrite and sphalerite structure, respectively, and the Blackman sum rule has been checked. The parameters of the dispersion oscillators have been obtained from dispersion analysis. The magnitude of the parameter γ characterizing the damping of the oscillator, γ = 0.061 (chalcopyrite structure) and γ = 0.110 (the sphalerite structure), exceeds the corresponding values for the compound GaP and InP; that is possibly due to stronger phonon‐phonon interaction in ZnSnP2. Using dispersion analysis and Kramers‐Kronig analysis the disperison of the refractive index and the dielectric constant due to the lattice vibrations has been calculated.
On the Phonon Drag Effect Contribution to the Electrical Conductivity of Semiconductors
Authors: Plâvitu C. N.
Published: July 2007

The contribution of the optical phonon drag effect to the electrical conductivity of a semiconductor with an important percentage of polar bond is calculated. It is found that this effect is significant in the high‐temperature range and smaller but not negligible in the low‐temperature range.
Electric Properties of Dislocations in p‐Type Germanium
Authors: Kryłow J.
Published: July 2007

The aim of the present paper is an explanation of the decrease in the carrier concentration found in p‐type germanium after deformation. The investigation shows that the observed effect is not necessarily connected with the donor action of dislocations and that it can also be caused by the precipitation of acceptors on dislocations. If we assume a donor action of dislocations then the donor level lies about 0.22 eV above the top of the valence band.
Resistance Minima in Nondilute CeLa and CeY Alloys
Authors: Elliott R. O. , Hill H. H. , Miner W. N.
Published: July 2007

Minima that may be indicative of a spin‐compensated magnetic state have been observed in the electrical resistivity data for certain nondilute, hexagonal CeLa and CeY alloys. Resistively‐determined Néel temperatures do not agree with those determined magnetically for CeLa alloys containing ⪆ 21 at% La.
Research of the Anisotropic Potential in Eu2(WO4)3 Single Crystals with 3 eV Samarium Recoil Atoms by Means of Nuclear Resonance Fluorescence
Authors: Abel F. , Kalus J.
Published: July 2007

The slowing‐down behaviour of 3 eV Sm152 recoil nuclei which are created by the neutrino emission from Eu152m was studied in a single crystal of Eu2(WO4)3 with the help of nuclear resonance fluorescence (NRF). The expected dependence of the NRF yield on the flight direction of the Sm nuclei in the anisotropic crystal potential was observed. The twofold rotational symmetry of the b0‐axis and the angle β of the monoclinic crystal reproduced themselves in the experimental results. The maximum variation of the NRF yield was (3.9 ± 0.1)%. — The model which uses a nonspherically symmetric parabolic potential

permitted the calculation of the theoretical NRF yield. The arbitrary parameter occurring in the model was determined by comparison with the experiment.
Quadrupole Broadening of Nuclear Magnetic Resonance Lines in Deformed Copper and Aluminum
Authors: Kanert O.
Published: July 2007

The nuclear magnetic resonance lines of Cu63 and Al27 in bulk polycrystalline copper and aluminum have been measured as a function of plastic deformation. The line shape of these signals shows a quadrupolar broadening from which the mean dislocation density of the deformed samples may be determined. It was found that in each the flow stress which is effective during the deformation is proportional to the square root of the dislocation density. — The NMR signal of a plastically deformed copper single crystal shows a dependence of the quadrupole perturbation on the direction of the external magnetic field H0 relative to the crystal axes. This results can be explained on the basis of the special position of the dislocations in the lattice.
Electronic Displacement in Tellurium by Mechanical Strain
Authors: Arlt G. , Quadflieg P.
Published: July 2007

The piezoelectric constants e11 and e14 of tellurium have been found by measurement to be 0.42 C m−2 and 0.17 C m−2. They are described by strain‐induced displacement of the electron distribution relative to the Te cores.
ESR Study of Paramagnetic Centres Formed by Introduction of Ca2+ in NaCl and NaBr Single Crystals
Authors: Nicula Al. , Fârcaş S. I. , Darabant Al.
Published: July 2007

The defects formed by introduction of Ca2+ ions in NaCl and NaBr single crystals and after UV irradiation at room temperature have been observed by the electron spin resonance method. Two types of paramagnetic centres have been detected: one with axial symmetry and the other with orthorhombic symmetry. The highly anisotropic g‐factor of these centres proves that the responsible electron for the observed absorption is not in an s state. The formed centres decay at approximate 400 °K.
Errors in the Numerical Calculation of the Moments of the ESR Absorption Curves
Authors: Buluggiu E. , Dall'olio A. , Varacca V.
Published: July 2007

When calculating the moments of the ESR absorption curves from the derivatives with the usual numerical integration method of the odd moments, an error is made due to the fact that one neglects a term with respect to the analytical integral. In the present work, we show that this error is remarkable for the second moments of a cut‐off Lorentzian curve and decreases the more the line shape approaches a Gaussian shape.