bluuebunny/crossref_metadata_2025 huggingface dataset:
Galvanomagnetic Properties of ZnxHg1−xTe Solid Solutions
Authors: Niculescu D. , Dziuba E. Z.
Published: July 2007

An investigation is made of the electrical conductivity and the Hall coefficient of ZnxHg1−xTe system with x = 0 and x = 0.2 as a function of the temperature and magnetic field in the ranges 77 to 400 °K and 250 to 1000 Gs, respectively. An effect of the “heavy carriers” on the galvanomagnetic properties is found. The additional conductivity due to these “carriers” has a temperature independent value. The energy gap for HgTe is estimated to Eg = −0.27 eV and Eg = −0.16 eV at the temperatures 77 and 300°K, respectively.
Majority Carrier Sweep‐out after Pulse Injection into Semiconductors
Authors: Lemke H.
Published: July 2007

After the removal of majority injecting voltages on semiconductors with traps a sweep‐out of free carriers in the field of the trapped space charge occurs resulting in a subthermal population of the majority band. A simple model leads to a system of Abel type differential equations, a closed solution of which could not be found. A “quasi‐stationary” approximation adequate to the experimental conditions relates the prominent features as sweep‐out time, depleted concentration, and recovery time to physically significant parameters and gives evidence of two different mechanisms of recovery: at high temperatures (relative to the trap depth) a competition between sweep‐out and dielectric relaxation, at low temperatures competition between retrapping and sweep‐out.
Theory of Surface Elastic Wave Excitement in Semiconductors with Low Rate of Surface Recombination of Current Carriers
Authors: Vagner I. D. , Ioffe I. V. , Shender E. F.
Published: July 2007

The instability of quasi‐neutral waves in semiconductors with two types of current carriers in electric and magnetic fields at low surface recombination rate is studied theoretically. It is shown that this instability causes the excitation of Rayleigh waves even if the drift velocity is lower than the surface wave velocity.
On the Mechanism of Heat Transfer in Ag2S and Cu2S
Authors: Okhotin A. S. , Krestovnikov A. N. , Aivazov A. A. , Pushkarskii A. S.
Published: July 2007

An analysis is made of the anomalous temperature dependence of the thermal conductivity of the β‐modifications of the semiconductors Ag2S and Cu2S. The activation model of heat transfer is used for the interpretation of these fluctuations. The calculations confirm that the conclusions are justified.
Photostimulated Electron Emission Spectra of Vacuum‐Ultraviolet‐Irradiated Ionic Crystals
Authors: Bichevin V. , Käämbre H.
Published: July 2007

By the investigation of the spectral characteristics of photostimulated electron emission it has been shown that F‐centres are created in NaCl, KCl, KBr, and KI single crystals by ultraviolet irradiation in the 5 to 11 eV region. The F‐centres are formed as a result of the photoproduction of excitons as well as electron–hole pairs, the exciton mechanism being especially effective. Under stimulation with visible light, electron emission appears from UV‐created F‐centres due to a two‐step photothermal process in crystals with sufficiently low electron affinity χ and by the usual photoemission mechanism in crystals with relatively high χ.
On the Spectra of Impurity Photoconductivity of n‐ and p‐Type Indium Antimonide at Low Temperatures
Authors: Ismailov I. M. , Nasledov D. N. , Smetannikova Yu. S.
Published: July 2007

The spectra of impurity photoconductivity of n‐ and p‐type indium antimonide at 6, 40, and 80 °K are investigated. The oscillations observed in the impurity photoconductivity of p‐type samples at helium temperature result from the interaction of hot holes and longitudinal optical phonons. It is found that the photoexcitation of electrons from the deep donor level to the conduction band in high electric fields leads to oscillatory impurity photoconductivity with periods equal to the limiting energies of the longitudinal and transverse acoustic phonons; the photocurrent value and relative amplitude of the oscillations depend nonlinearly on the electric field. The field dependence of the electron lifetime is evaluated.
On a Specific Mechanism of Absorption of Electromagnetic Waves by Impurity Polarons
Authors: Klinger M. I. , Blakher E.
Published: July 2007

A theory is developed for a polarization mechanism of absorption of electromagnetic waves by polarons localized on impurity centres with an appropriate structure. The coefficient of this absorption shows a specific frequency (ω) dependence both at low and at high ω and some basic features (at high ω) similar to those for the high‐frequency conductivity for small polarons and for the well‐known resonance impurity polaron absorption.
ESR Studies of V‐Centres in NaCl (Ca++) Crystals
Authors: Watterich A. , Gécs M. , Voszka R.
Published: July 2007

In OH‐free grown NaCl (Ca++) crystals three paramagnetic V‐centres can be observed under different conditions. Irradiation of the crystals with X‐rays at liquid nitrogen temperature produces VK‐centres, irradiation at dry ice temperature or warming up the VK‐centre causes the V‐centre to appear. At room temperature X‐irradiation leads to a paramagnetic centre which may be considered with high probability to be a VF‐centre.
On the Anisotropic Microwave Conductivity in the Hot‐Electron Region of n‐InSb
Authors: Richter K. , Bonek E.
Published: July 2007

It is shown by experiment that the small‐signal microwave conductivity of n‐type InSb at 77 °K and 35 GHz decreases considerably, when an electric de field in excess of 10 V/cm is applied simultaneously. Further, a marked anisotropy with respect to the direction of the applied de field is observed. A sample with higher electron mobility shows a stronger anisotropy than a sample with lower mobility. It is possible to measure the momentum relaxation time because of the occurrence of strong relaxation effects. The microwave conductivity, which is dominated by these effects, can be calculated by assuming mean momentum and energy relaxation times according to Kopetz and Pötzl. The applicability of these relaxation times to the hot‐electron region of InSb is proved by the good agreement between experimental and theoretical results.
Antiphase Boundaries and Twins Associated with Ordering of Indium Vacancies in β‐In2S3
Authors: van Landuyt J. , Amelinckx S.
Published: July 2007

β‐Indium sulfide crystals have been studied by electron microscopy and electron diffraction. From an analysis of the defective spinel structure, different types of ordering defects are predicted. Ordering twins and two types of antiphase domains have been observed, and their analysis is in complete agreement with the proposed models. Heating experiments enabled a distinction to be made between the defects associated with the tetrahedrally surrounded cations and those in octahedral sites. A mechanism is proposed for the two transitions previously observed in this material: The transition at 420 °C is attributed to the disordering of tetrahedral cations, whereas the transition at 750 °C is associated with the disordering of the octahedrally surrounded cations.
Photographs of the Diffraction Pattern of Ferromagnetic CrBr3
Authors: Fischer F.
Published: July 2007

Sharp diffraction patterns of the Fresnel type, which are free from distortion, have been photographed using monochromatic light and fixing the crystal to a 50 μm hole diaphragm cooled to 20 °K in an optical cryostat. Temporary saturation of the magnetization gives three different types of patterns according as the magnetic field forms an angle of 90, 45, or 0° with the crystal c‐axis. Linearly polarized light gives interference spots of the first order polarized perpendicular to the primary light. An interpretation is presented considering also the circular dichroism. Second‐order spots polarized parallel to the primary light are probably due to the domain walls. Above an activation temperature of TA = 31.5 °K the domain walls become mobile. Hereby the 90° and the 45° type change into the 0° type. The latter also appears after cooling from above TC.
Electrical Breakdown in Germanium Exposed to Infra‐Red Radiation
Authors: Brandt E. H. , Güth W.
Published: July 2007

Infra‐red irradiation accelerates the build‐up of an avalanche in weakly n‐doped Ge and increases the steady‐state current. Both effects occur even if the photo‐current is very small at the beginning of the avalanche or at fields below the threshold of a breakdown. The dependence on the wavelength of the breakdown current has been measured and the time dependence of the avalanche rise investigated. An explanation of the effect of the radiation has been offered.
Dirt in Slater's Split‐Band Model of Antiferromagnetism
Authors: Johansson B. , Berggren K.‐F.
Published: July 2007

The effect of impurities on the split‐band model is analysed. As in the case of a dirty superconductor and a dirty excitonic state gaplessness is found for a certain range of impurity concentration. Implications on transition‐metal oxides (and sulphides) are briefly discussed.
Ellipticity of π/2‐Spin Waves for Cubic Crystals
Authors: Voigt F.
Published: July 2007

The ellipticity of a spin wave dependences on the dipole‐dipole‐interaction and the crystalline anisotropy energy. It will be shown that when only magnons having a single wave vector are excited in the parallel‐pumping experiment the ellipticity may be estimate from the dc magnetic fields for the minimum of the butterfly‐curve at the [100]‐ and [111]‐magnetization direction. Only the magnetization and the gyromagnetic factor must be known from other measurements, not the constants of the crystalline anisotropy energy.
The Fine Structure of Spots in Electron Diffraction Resulting from the Presence of Planar Interfaces and Dislocations V. Multiple Beam Case
Authors: Gevers R. , Serneels R. , van Landuyt J. , Amelinckx S.
Published: July 2007

A description is given of the fine structure of the electron beams transmitted and scattered by a plate‐shaped foil containing a stacking fault or an anti‐phase boundary inclined with respect to the surface. It is assumed that there are n strong diffracted beams. The transmitted and each strong scattered beam consists of n (n + 1) + 1 beams, very slightly different in orientation, and which give rise to the appearance of satellites of the diffraction spots. The geometry and the intensities of the satellite configurations are discussed. General properties can be derived from the formulation developed in the paper. Electrons leaving the crystal in a satellite beam direction are those which have changed from one wave field to another on crossing the fault boundary. The influence of the anomalous absorption, important for a thick crystal, is also examined. Satellite beams formed by electrons moving in a strongly absorbed wave field before or (and) after crossing the stacking fault, will be weak. A bright satellite is expected if one or both of these fields are easily transmitted. Finally it is shown that the intensities of the different satellite beams are not the same in different parts of the faulted region.
Investigation of Dynamic Characteristics of Ferromagnetics at Low Temperatures
Authors: Škrinjar M. J. , Tošić B. S.
Published: July 2007

The low‐temperature characteristics of ferromagnetics with the effective spin S = 1/2 are investigated using the exact Bose representation of spin operators. The main result of the investigation is that due to anharmonic effects in the magnon system the Bloch's formula for magnetization has a correction which is proportional to the square of the temperature.
Initial Susceptibility of Ferrimagnetic Materials and Topography of Domain Walls
Authors: Globus A. , Duplex P.
Published: July 2007

Observations are reported, that ferrimagnetic materials which are identical in their fundamental properties (composition, Ms, Tc, λs) as well as in their granular structure (porosity, size, and shape of grains) can present very different thermal spectra of initial susceptibility. This behaviour is found to be general for the many compositions studied. The proposed interpretation is based on the existence of different degrees of wall continuity accross the grain boundaries. It is suggested that the degree of wall continuity is associated with the relative crystallographic axes orientation of the grains. The experimental results of the frequency spectra of intial susceptibility support this hypothesis. It is also observed that the hysteresis of thermal spectra is quite general and this in turn can be related to the wall topography.
Electromigration in Liquid NaK Alloys
Authors: Jousset J. C. , Huntington H. B.
Published: July 2007

The relative electromigration of Na and K atoms in liquid NaK alloys has been investigated for two compositions, 0.47 and 0.30 K (atom. conc.). This effect has been found to be in the opposite direction for the two alloys; Na ions go towards the anode for the 0.47 K concentration and towards the cathode for the 0.30 K. The interpolated concentration of this reversal is found to equal 0.39 K, in agreement with the result of Drakin and Maltsev [13]. The variation of the coefficients of “electron drag” for both components has been measured as a function of temperature in the range of 85 to 300 °C, where they behave anomalously. In both the dilute and concentrated alloy regions the directions of the mass flux agree with theoretical predictions but the magnitudes are smaller by nearly a factor of 10. A possible explanation may be that mass transport proceeds through the motion of large coordinated complexes. The breakup of these complexes at higher temperature might explain one aspect of the anomalous temperature dependence.
Field Emission from p‐Type Si
Authors: Fursey G. N. , Egorov N. V.
Published: July 2007

The nonlinear field emission behaviour in dependence on temperature and light intensity was studied in p‐type silicon crystals, whose surfaces were prepared by high‐field evaporation in vacuo. The voltage drop along the emitter measured by the retarding potential technique and the size of the emission pattern were determined for every point of the Fowler‐Nordheim plot. The curvature of the current—voltage curves for Si has more distinct character than it was observed earlier for Ge. The region of “absolute field emission saturation”, which extends over a wide range of applied voltage variation was found in the Fowler‐Nordheim plots. The emission current—voltage behaviour appreciably depends on sample history and especially on temperature treatments. Sample heating to 400 to 450 °C during bake‐out fully distorts the field emission data in Si. Light and temperature produce the same effect on the field emission current.
Wasserstoff in Metallen als Beispiel für ein Gittergas mit Phasenumwandlungen
Authors: Alefeld G.
Published: July 2007

Aus Phasendiagrammen und Löslichkeitsmessungen für Wasserstoff in Metallen kann gefolgert werden, daß es in dem von der Metallmatrix aufgespannten Raume für den interstitiell gelösten Wasserstoff — analog zu freiem Wasserstoff — die Phasenumwandlung gasförmig‐flüssig gibt. Der kritische Punkt der Mischungslücke wird mit dem kritischen Punkt für die Phasenumwandlung gasförmig‐flüssig identifiziert. Aus Löslichkeitsmessungen lassen sich die Zustandsdiagramme für das Gittergas bestimmen. Diese zeigen den für ein nichtideales Gas charakteristischen Verlauf, einschließlich des kritischen Punktes und des durch die Koexistenzkurve begrenzten Zweiphasengebietes. Auch die Diffusions‐konstante des gelösten Wasserstoffs, die den für Festkörpersysteme bei Raumtemperatur üblichen Wert um etwa 10 Größenordnungen überschreitet, ist vergleichbar mit der in freien Flüssigkeiten. Wasserstoff in Metallen kann also in erster Näherung als ein Beispiel für das theoretisch untersuchte Gittergas mit seiner Phasenumwandlung zur Flüssigkeit angesehen werden.
The Chemical and Isoconcentration Diffusion of Zn in AlSb
Authors: Showan S. R. , Shaw D.
Published: July 2007

The chemical diffusion of Zn in AlSb has been investigated as a function of temperature in the range 650 to 933 °C and as a function of Zn surface concentration. The diffusion coefficient is found to be concentration‐dependent and shows a behaviour similar to that observed in GaAs, GaP, and InP. Isoconcentration diffusion of Zn at 933 °C in AlSb is found to be strongly concentration‐dependent. Quenching of Zn‐diffused samples shows that the substitutional Zn is a single‐level acceptor which is completely ionized at the diffusion temperature. It is concluded that the Longini model provides a satisfactory interpretation of the diffusion processes. Substitutional Zn in AlSb is also found to show retrograde solubility.
Infrared Measurements on CdS Thin Films Deposited on Aluminium
Authors: Proix F. , Balkanski M.
Published: July 2007

The reflectivity spectra of three CdS thin films (thickness 0.086, 0.33, and 0.66 μm) deposited on aluminium have been determined at room temperature. The measurements were carried out in the spectral range 180 to 740 cm−1, at an incidence of 45°, for light polarized with the electric field in the plane of incidence. A small absorption peak is observed near ωTO for the thicker samples, and a much stronger absorption peak near ωLO for all samples. The results are analysed in terms of the theory of Fuchs and Kliewer. The frequencies of the peaks and the partial widths associated with the virtual modes are in very good agreement with the theory. It is also found that the anharmonic width of the peaks is much larger than in CdS single crystals.
The Complete Dependence on Crystal Orientation of the Hall Coefficient of Copper
Authors: Saeger K. E. , Lück R.
Published: July 2007

A technique has been developed for measuring the Hall coefficient which is based on the invariance of the antisymmetric part of the resistivity tensor with respect to rotational transformation. This technique permits the Hall coefficient for any orientation to be determined on one single crystal. In this paper it has been applied to copper. The results thus obtained are used for the calculation of the Hall conductivity which, in turn, yields information on characteristic properties of the Fermi surface.
Electrical Switching Phenomena in Transition Metal Glasses under the Influence of High Electric Fields
Authors: Drake C. F. , Scanlan I. F. , Engel A.
Published: July 2007

A mechanism is proposed to account for the phenomena observed in many vitreous systems of field‐induced switching between two or more conducting states. Conduction in the high resistance state is assumed to involve electron hopping between non‐identical sites. The vitreous nature of the systems precludes extrinsic conduction, and the equilibrium number of intrinsic carriers is shown to be a function of the degree of inequality of site configurations, temperature, field strength, and dielectric constant. The carrier mobility is a function of averaged distance between sites, of temperature, and dielectric constant. Dc conduction and dipole production and orientation are shown to be interrelated processes. The consequent non‐linear dependence of polarization on field leads to a quasi‐ferroelectric reorganization of the structure at a critical field strength. The structural reorganization makes the site environments more nearly identical, and thereby delocalizes the excess electrons on one of the sites producing semi‐metallic conduction. Local energy dissipation by the turn‐off pulse raises the lattice temperature sufficiently to allow the structure to relax to its initial state. The quantitative implications of the theory are developed, and compared with measurements on some copper glasses.
Some Numerical Results on Quasiparticle Properties in the Electron Gas
Authors: Lundqvist B. I.
Published: July 2007

Numerical results for some quasiparticle properties of an interacting electron gas are presented. New data are given for highly excited electrons. It is shown that there is a characteristic momentum dependence in the energy, damping rate, and spectral weight of the quasiparticle. The results are calculated using a self‐energy expression to the lowest order in the effective (RPA) interaction between the electrons. Well‐defined peaks in the spectrum are obtained for all momenta, and in this sense it is concluded that the quasiparticles have a physical meaning everywhere in momentum space.
Electroabsorption of CdS and CdSe Single Crystals in the Exciton Region
Authors: Lange H. , Gutsche E.
Published: July 2007

Electroabsorption spectra in the exciton region were measured on very thin CdS and CdSe single crystals at 77 °K in the field range 1 × 103 to 2.4 × 104 V/cm for both polarizations of incident light with respect to the c‐axis. The electroabsorption spectra exhibit much more details than electroreflection spectra know so far. The variation of peak positions and peak heights with electric field strength is different for different parts of the spectrum. Some of the peaks shift to lower and others o higher energies with increasing field strength. The spectra can be interpreted in terms of a second order Stark shift, field induced line broadening and Franz‐Keldysh type interband oscillations.
The Work Function in Simple Metals
Authors: Schneider T.
Published: July 2007

We have applied the pseudopotential approach for a calculation of the work function for simple metals. The alkali metals, magnesium, and aluminium are treated quantitatively, using a model‐pseudopotential determined from the measured phonon dispersions or the elastic constants. Our results indicate that the correlation energy contributes significantly to the work‐function. Generally, good agreement is achieved.
Contribution of the Piezoelectric Scattering to the Energy Scattering of Conduction Electrons in Semiconductor Thin Films
Authors: Ilkovič V.
Published: July 2007

The parameter β characterizing the interaction between the conduction electrons and the lattice is calculated for a thin film of non‐degenerate semiconductors using the electrontemperature approximation taking into account the scattering by the deformation and the piezoelectric potential. It is shown that the energy scattering of the conduction electrons on the piezoelectric potential in thin films of n‐InSb is important in the temperature region below 10 °K.
A Field ion Microscope Investigation of 10 MeV Proton Damage in Iridium
Authors: Petroff P. , Washburn J.
Published: July 2007

Annealed iridium specimens of 99.99% purity were irradiated at 5 °K with 10 meV protons in a field ion microscope attached to a cyclotron. Contrast effects due to point defects and their clusters were analyzed. By a field evaporation technique the point defect distribution in the bulk was investigated. Interstitial migration to the surface was directly observed upon annealing in the temperature range 15 to 42 °K. The decrease in the bulk concentration of interstitials during annealing in the temperature range 5 to 300 °K indicated that stage I is caused by interstitial migration to close‐by vacancies and traps and stage II was due to interstitial detrapping. Damage caused by irradiation at 5 °K was compared to that introduced at 300 °K. The damage which was large voids (400 to 500 vacancies) and dislocation loops suggested a different formation mechanism in the specimens irradiated at higher temperature.
Elastic Constants of the Fluxoid Lattice Near the Upper Critical Field
Authors: Labusch R.
Published: July 2007

The elastic constants of the fluxoid lattice are calculated in terms of the reversible magnetisation curve by taking the appropriate derivatives of the free energy of the fluxoid assembly. The expressions obtained in previous work for the compressional modulus and for the shear modulus c44 in magnetic fields well below Hc2 are confirmed and their validity over the entire range of field between Hc1 and Hc2 is established. A new expression is derived for the shear modulus c66 in high fields. It turns out that c66 goes quadratically to zero if the applied field approaches Hc2.
The Mechanical Behaviour of an Iron—11 at% Molybdenum Alloy in the Temperature Range 295 to 1100 °K
Authors: Rawlings R. D. , Newey C. W. A.
Published: July 2007

The effect of precipitation of an intermetallic compound on the mechanical behaviour of an Fe—11 at% Mo alloy has been studied by means of compression tests in the temperature range 295 to 1100 °K. At temperature up to 700 °K for the well‐aged conditions of the alloy and 875 °K for the solution‐treated and slightly aged states, the temperature dependence of the yield and 0.2% proof stresses can be accounted for by the change in the elastic modulus with temperature. For the well‐aged conditions in the temperature range 700 to 950 °K the yield strength was temperature and strain‐rate sensitive. It is concluded that in this temperature range, deformation is determined by the diffusion‐controlled motion of dislocations past the precipitate barriers. Above about 950 °K all conditions of the alloy exhibited a similar, and large, temperature dependence of the yield strength; in addition, secondary creep occurred at the imposed strain rate and the creep stress was found to be independent of the size and distribution of the precipitate. The very high values of the apparent activation energy for yield and secondary creep found above 950 °K are considered to be due to an anomalous change in the activation energy for diffusion during the Curie transformation.
Point Defects in Ferromagnetic Thin Films
Authors: Sukiennicki A. , Zagórski A.
Published: July 2007

The effect of point defects (vacancies, magnetic impurities) on the spontaneous magnetization of thin films is computed in the molecular field approximation. It is found that the magnetization distribution around the defects is not spherically symmetric as in the case of the bulk materials; it is modified by the film surface. The results may be applied generally to all surfaces of bulk materials.
Consequences of Bloch's Theorem on the Dynamical Theory of Electron Diffraction Contrast
Authors: Metherell A. J. F. , Fisher R. M.
Published: July 2007

Some consequences of Bloch's theorem on the diffraction of fast electrons in solids are considered. It is shown that the absorption coefficients of the various crystal wavefields excited in a crystal by the incident electron are periodic functions of crystal orientation. As a result it is shown that the two‐beam theory, when applied to the calculation of the absorption coefficients, results in a poor approximation. Recently several authors have shown that the higher‐order even reflections, such as the 222 reflection in Al or the 400 reflection in MgO, become vanishingly weak at certain critical values of the incident beam potential. From an investigation of the symmetry properties of the crystal wavefields a simple physical picture of this effect is obtained, and it is shown that at the critical voltage a reversal of the crystal wavefield symmetry occurs.
On the Theory of Surface States in Three‐Dimensional Crystals
Authors: Scherer M. , Phariseau P.
Published: July 2007

The existence of surface energy states of electrons in solids has been proved by Heine by matching the wave functions at the boundary plane. Starting from this general theory, we calculate the surface energy bands in three‐dimensional crystals with one atom per unit cell. Not only a semi‐infinite lattice but also a three‐dimensional crystal slab is considered. The method developed in this paper is a generalization of the Green's function method of Kohn and Rostoker for calculating the energy bands in infinitely extended crystals.
Capture of Gas Atoms Dissolved in a Solid by a Moving Gas Bubble
Authors: Ya. Mikhilin E.
Published: July 2007

The capture of dissolved gas atoms in a solid by a bubble moving in it is considered. The conditions are analyzed under which the bubble movement results in considerable changes of the gas quantity entering the bubble.
A Possible After‐Effect in Coarse‐Grained MnZn Ferrite of High Permeability
Authors: Buck O. , Roess E.
Published: July 2007

MnZn ferrites of high initial permeability and different grain sizes have been studied. It was found that in materials with coarse grains the permeability and the harmonic distortion increase very rapidly with increasing induction whereas nominally the same materials with fine grains do not show this increase. A “pinning” interaction between ingrown pores and magnetic domain walls appears to be the cause of the rapid increase of permeability and distortion in the coarse grain ferrites. This interaction also causes the real part of the permeability and the maximum of the distortion to drop off at frequencies far below the eddy current cut‐off frequency and the gyromagnetic resonance frequency.
Beta‐Excitation of CdS Crystals
Authors: Schubert G. , Schnürer E.
Published: July 2007

Beta‐excitation of CdS crystals with a majority blocking cathode and an ohmic anode gives rise to charge pulses in an integrating network. The analysis of the pulses allows to evaluate effective mobilities and lifetimes of the carriers and the electron—hole pair production energy. The values obtained are resonable and in agreement with those found by other authors, but the measured effective lifetimes are not identical with the high lifetimes of majority carriers typical for CdS in usual photoconductivity measurements. Care had to be taken to avoid space charge accumulation.
Short‐ and Long‐Range Order in Au3Cu
Authors: Airoldi G. , Asdente M.
Published: July 2007

The temperature dependence of the thermoelectric power of the Au3Cu alloy was measured for different states of order. While the disordered and the long‐range ordered states show qualitatively the same trend as the Cu3Au alloy, the short‐range ordered state shows different behaviour and a certain analogy with the long‐range ordered states. These results are discussed in connection with the new Bragg planes induced by the superlattice.
Latent Hardening in Rock‐Salt Type Crystals
Authors: Nakada Y. , Keh A. S.
Published: July 2007

The latent hardening in nine different crystals having the rock‐salt structure was studied as a function of prestrain. The latent hardening of a LiF crystal was also measured as a function of temperature. It was found that the latent hardening ratio of a crystal increases from 1.0 at zero strain to a maximum at about 0.5 to 1.5% compressive strain, then decreases to a constant value somewhat above 1.0. The maximum latent hardening ratio varies from 3.9 for LiF to 1.2 for AgCl. The difference in stress between the latent and the primary system in LiF remained essentially constant at all temperatures from 450 to 4 °K. The latent hardening ratio at 0.5% prestrain is 3.1 at 300 °K and 1.6 at 4 °K. Latent hardening was observed even above 300 °K where the flow stresses of the primary and the latent systems are essentially independent of strain rate and temperature. Dislocation distribution, revealed by etch pitting, was uniform during the primary slip, but was confined to widely separated bands during the latent hardening test. It is concluded that latent hardening in rock‐salt type crystals is caused primarily by the interaction of the glide dislocations in the latent slip system with the dipoles and dislocations in the primary slip system according to the dislocation reaction

.
Trapping Levels in the Silicon—Silicon Nitride System
Authors: Kendall E. J. M.
Published: July 2007

The silicon—silicon nitride system has been examined using thermally stimulated current (TSC) techniques. The nitride was found to contain electron traps at between 0.50 and 0.90 eV below the bottom of the conduction band. A distribution of traps at or near the Si—Si3N4 interface and about 0.10 eV below the conduction band of the silicon was found. The TSC spectra clearly showed the dependence of the trap occupancy and trap structure upon applied electric field and temperature. Electron microscope and X‐ray work indicated that the nitride layers were not truly amorphous but contained very small crystalline areas.
On the Mechanism of Charge Carrier Generation in Thin Layers of Molecular Associates
Authors: Silinsh E. A. , Taure L. F.
Published: July 2007

Measurements are made of the dependence of the electrical current on voltage and sample thickness for thin layer systems of some molecular associates (MA) with intermolecular hydrogen bonds. The results show that the MA under investigation may be divided into two groups with respect to the mechanism of charge carrier generation in high electrical field (ϵ = 104 to 106 V/cm). For the first group of MA, the ohmic region of C—V characteristics is followed by a non‐linear injection region of space charge limited current (SCLC) type with a quasi‐continuous exponential trap distribution. At higher electrical fields (ϵ > 105 V/cm) the injection region passes to the dominating bulk ionization region. For the second group of MA the bulk ionization region follows directly after the ohmic region. The main experimental criteria of both mechanisms are discussed.
Ětude de la décomposition spinoïdale au microscope électronique dans les alliages CuNiFe
Authors: Cadoret R. , Delavignette P.
Published: July 2007

L'étude du contraste a été effectuée en prenant comme modèle le mécanisme de décomposition spinoïdale prévu par Cahn [1 à 3] pour un alliage binaire cubique, dont l'énergie élastique est minimum suivant une direction β parallèle à <100>. Les contrastes effectivement observés au microscope électronique sur deux alliages Cux—(Ni0,7Fe0,3)y de composition initiale différente sont en accord avec l'analyse théorique de Cahn: déformation de la variation sinusoïdale de la composition avec le temps, manifestation plus rapide des phénomènes de croissance dans l'alliage de composition initiale le plus asymétrique.
Utilization of Symmetry in Solving the Boltzmann Equation
Authors: Mann E.
Published: July 2007

Boltzmann's integral or integro‐differential equation may be reduced to a finite system of linear algebraic or simple integral equations if the kernel (the transition probability) is degenerate. This happens for elastic scattering of electrons by localized defects if the scattering is described in terms of Wannier functions. It is shown how the transition probability may be represented as a sum of terms transforming according to the irreducible representations of the point group of the problem. As a consequence, the system of linear equations is split into smaller systems. Since the calculation of the electrical current density involves only a few of these representations, only a few systems of smaller order need to be solved. The reduction procedure is described in detail for three examples with cubic, tetragonal, and orthorhombic symmetry.
On the Relief of Ordering Strains by Twinning
Authors: Tanner L. E. , Ashby M. F.
Published: July 2007

The relief of strains associated with certain phase transformations in alloys is discussed. The emphasis is on twinning in the course of cubic → tetragonal ordering. These ideas are applied to the structural observations of Al → DO22 and Al → Ll0 transitions.
Theory of Stark Effect in Crystals
Authors: Enderlein R. , Keiper R. , Tausendfreund W.
Published: July 2007

The change of the optical interband absorption of non‐conducting crystals in an external electric field is investigated. The degeneracy of the band structure is considered. The modification of the absorption by the electric field is shown to be the superposition of the Stark effect and of the Franz‐Keldysh effect. In particular, the transitions Γ → Γ and X5 → X5 in diamond type crystals are considered. The transition Γ → Γ shows a quadratic Stark effect and the transition X5 → X5 a linear one.
Relaxation von Fehlstellendipolen in AgCl‐Kristallen
Authors: Kunze I. , Müller P.
Published: July 2007

Es wird über Messungen des thermischen Depolarisationsstromes (ITC) in mit V, Cr, Mn, Fe, Co, Ni, Cd und Pb dotierten AgCl‐Einkristallen berichtet. Die durch Assoziation aus Fremdkationen und Leerstellen gebildeten und durch Abkühlung im statischen Feld teilweise ausgerichteten Dipole verursachen bei Erwärmung mit 2° K/min durch ihre Reorientierung einen Depolarisationsstrom mit einem Maximum bei etwa 110° K. Aus diesen elektrischen „Glowkurven”︁ lassen sich die Sprungenthalpien, die Frequenzfaktoren und, bei bekannter Zahl der Dipole, auch die Dipolmomente bestimmen. Bei AgCl:Ni, AgCl:Cd und AgCl:Pb treten einfache ITC‐Kurven mit nur einem Maximum auf, während die in allen übrigen Fällen erhaltenen komplizierteren Meßkurven als Summe zweier einfacher ITC‐Kurven aufgefaßt werden können. Verursacht werden diese Doppelkurven durch die zwei Relaxationsmöglichkeiten, die bestehen, wenn die Leerstellen außer den nächsten Nachbarplätzen auch die übernächsten Nachbarplätze der Fremdionen besetzen.
Theory of Anharmonic Crystals. II. Linear Chain
Authors: Plakida N. M. , Siklós T.
Published: July 2007

The properties of the monatomic linear chain with nearest neighbour interaction are considered at fixed length and at constant external tension applying the dynamical theory of the anharmonic lattice developed in our previous work. The vibrational frequency, the damping, the internal energy, the specific heat, the average length and tension are calculated. It is shown that in the case of constant external tension the chain becomes unstable at sufficiently high temperature or at sufficiently high zero‐point energy. The critical parameters are obtained and the behaviour of the thermodynamical quantities in the vicinity of the critical point are investigated.
Polarity Inversions of the Photo‐Hall E.M.F.
Authors: Sakalas A. , Viščakas J.
Published: July 2007

The inversion of the sign of the photo‐Hall voltage is investigated in almost intrinsic semiconductors being illuminated with light in the region of the fundamental absorption. It is shown theoretically that single or double inversions are possible if only one type of centres is considered. The inclusion of traps gives single, double or triple inversions. Numerical solutions of these cases are represented. The experimental data agree well with the theoretical curves.
Recovery of Dilute Al–Si Alloys Cold‐Worked at −195°C
Authors: Hegazi A. , Kovács I. , Nagy E.
Published: July 2007

Isochronal annealing data are presented covering the whole range of temperature (−195 to 600°C) for cold‐worked dilute Al–Si alloys. The role of the Si atoms in the creation of defects during the deformation and the recovery process is discussed.
Differential Reflection Spectra of Heavily Doped Silicon and Germanium in the Ultraviolet Spectral Region
Authors: Volfson A. A. , Subashiev V. K.
Published: July 2007

The effect of heavy doping on the reflection spectra of silicon and germanium is investigated by measuring the fractional change in reflectance, ΔR/R, between pure and doped materials. This effect arises from the narrowing of the forbidden gap in heavily doped materials. The form of the ΔR/R spectrum allows to reveal the critical points of the band structure, as in electro‐, piezo‐, or thermoreflectance measurements.
Photoluminescence of CdIn2S4 and Mixed Crystals with In2S3 as Related to Their Structural Properties
Authors: Czaja W. , Krausbauer L.
Published: July 2007

In this paper experiments on photoluminescence (emission and excitation spectra) of CdIn2S4 crystals and of mixed crystals with In2S3 at 77°K are reported. The results are interpreted on the basis of the partial inversion of the thiospinel CdIn2S4. In CdIn2S4 the two emission bands observed in the red spectral region are ascribed to a Cd ion at an octahedral site and an In ion at a tetrahedral site. This model describes the intensity and wavelength variation of the photoluminescence of the mixed crystal system CdIn2S4/In2S3 surprisingly well. Evidence is given that the energy gap in all these crystals is indirect. In an appendix some etching procedures are listed.
Orientation Contrast from Inclusions (Experiment)
Authors: Guyot P.
Published: July 2007

The diffraction contrast in transmission electron microscopy is studied for alumina particles dispersed in an aluminium matrix. The position of the inclusions in the foil is measured by stereomicroscopy. There is a good agreement with the intensity profiles previously calculated on the basis of the two‐beam dynamical theory for non‐diffracting inclusions in a diffracting matrix.
Selection Rules for the Space Group C (Wurtzite)
Authors: Streitwolf H. W.
Published: July 2007

A complete list of selection rules for the space group C is given. The general results are applied to critical points, direct optical transitions, and second‐order processes in infrared lattice absorption and the Raman effect.
Investigation on the Magnetization Structure of Polycrystalline Uniaxial Ferrites with the Torsion Pendulum Method. I. Calculation of the Magnetic Stiffness
Authors: Voigt C. , Hempel K. A.
Published: July 2007

Using the formulas for the magnetic stiffness (torque per radian) of a ferromagnetic single crystal the stiffness of a polycrystalline sample performing small rotational oscillations in a homogeneous magnetic field with the axis of rotation perpendicular to the field direction is calculated. The sample is assumed to consist of non‐interacting crystallites with positive uniaxial magnetic anisotropy. The crystallites may be either in the single domain state or may be splitted up into domains according to the phase theory. The orientation distribution of the crystallites is supposed to have rotational symmetry with respect to a preferred direction.
Thermal Expansion of Silicon and Zinc Oxide (II)
Authors: Ibach H.
Published: July 2007

Coefficients of thermal expansion α‖c and α ⊥ c between 4 and 800°K have been measured for zinc oxide using an interferometric and a capacitance method. Thermal properties of wurtzite lattices (two coefficients of thermal expansion and a pyroelectric constant) can be described in terms of three thermal equations of state. Two mechanical and one electrical Grüneisen parameters are defined and their temperature dependence is calculated from experimental results. The high‐ and low‐temperature limits of the Grüneisen parameters are compared with results obtained in other experiments. The values predicted from a rigid ion model are discussed.
Shock‐Induced Substructural Changes in Prestrained Iron
Authors: Mahajan S.
Published: July 2007

Deformation structures of iron samples prestrained to various amounts prior to their exposure to 50 and 100 kbar shock waves have been examined by transmission electron microscopy. On shocking, the regions which had deformed during prestraining exhibit dislocation configurations characteristic of large‐strain room temperature deformation, and the undeformed areas develop substructures representative of very low‐temperature conventional deformation. Interactions between shock‐induced dislocations have also been analysed. Passage of a 100 kbar shock wave through samples prestrained 20% causes localized recrystallization. Experimental evidence favours the formation of nuclei for recrystallization by the coalescence mechanism.
The Energy Distribution of Field‐Emitted Electrons from GaAs
Authors: Hughes O. H. , White P. M.
Published: July 2007

Measurements of the energy distribution of field‐emitted electrons from clean GaAs surfaces indicate that the emission originates from the valence band. The distributions are found to be considerably wider than is predicted by theory despite the high resolution of the apparatus. The Fermi level at the surface of low‐resistivity n‐type material is found to be stabilized 0.54 eV below the conduction band edge indicating a high density of surface states. The surface state density is estimated to be greater than 2.8 × 1013 cm−2. Emission from within the forbidden gap is also reported.
Mechanical Behaviour of Crystals with Twinned Structure
Authors: Aoyagi T. , Sumino K.
Published: July 2007

The internal friction and the stress–strain behaviour are investigated on three kinds of materials which contain many twinned regions. A relaxation peak of internal friction with the activation energy (0.63 ± 0.03) eV is observed in an 89 at% manganese–copper alloy. The peak is thought to associated with the elementary process in the motion of surface dislocations (twin boundaries). Plastic flow possibly due to the motion of twinning surface dislocations is observed at relatively low stress level in this alloy. The relaxation peak is not found in gold–46.1 at% cadmium and indium–21 at% thallium alloys. Characteristics in a pseudo‐elastic flow due to the motion of twinning surface dislocations are examined on the gold–cadmium alloy.
Experimental Determination of Intrinsic Resistive Stress for Twinning Surface Dislocations
Authors: Sumino K.
Published: July 2007

The intrinsic resistive stress for twinning surface dislocations is determined from the analysis of the experimental results obtained in a previous paper [10]. The intrinsic resistive stress is expressed in terms of G′/G which is a ratio of the theoretical shear strength for twinning along a twin boundary to that in a perfect crystal. It is found that G′/G < 0.20 for 89 at% manganese–copper alloy and G′/G = 0.75 × 10−2 for gold–46.1 at% cadmium alloy.
X‐Ray Investigation of Lattice Deformations in Silicon Induced through High‐Energy Ion Implantation
Authors: Bonse U. , Hart M. , Schwuttke G. H.
Published: July 2007

X‐ray interference fringes observed in X‐ray topographs of silicon crystals bombarded with high energy ions (dose > 1015 ions/cm2) are described. The X‐ray fringes are used to analyze the deformation state of the crystal. It is shown that the bombarded crystal is a special kind of bicrystal composed of a thick perfect bulk crystal topped by a thin practically perfect layer crystal. Both crystals have the same crystallographic orientation and the same lattice constant but are separated by a small rigid body displacement. Contrast and geometry of the observed X‐ray patterns agree with the theoretical patterns calculated by Bonse and Hart [1] on the basis of a layer/bulk bicrystal model, and are also supported through transmission electron microscopy results. The ion range calculated from the interference fringes is in good agreement with the experimentally determined range.
F‐Centers in BaO
Authors: Mann K. E. , Holroyd L. V. , Cowan D. L.
Published: July 2007

Using ESR the isotropic and anisotropic hyperfine constant and the quadrupole interaction were determined for the nuclei (137Ba and 135Ba) in the vicinity of F‐center in BaO.
Electric Conductivity and Hall Effect in Evaporated Cadmium Selenide Films
Authors: Berger H. , Jäniche G. , Grachovskaya N.
Published: July 2007

Conductivity and Hall effect were investigated on evaporated CdSe films either non‐treated or annealed at 400 and 700°C. The measurements are performed in the temperature range from −150 to 400°C. In the lower temperature range the mobility of electrons follows an exponential temperature dependence of the form μeff = μ0 exp (– ΔE/kT) typical for polycrystalline films, which is not only determined by scattering mechanisms alone but also by the numbers and properties of potential barriers at the crystallite boundaries. These properties of polycrystalline film structure also explain the dependence of conductivity and mobility on film thickness found in non‐treated CdSe films. In the high temperature range conductivity and electron concentration strongly increase, indicating a self‐activated conductivity mechanism. The conduction electron concentration is determined here by thermal intrinsic disorder of lattice atoms.
Transport Properties of Indium Antimonide Thin Films
Authors: Berchtold K. , Huber D.
Published: July 2007

High mobility InSb thin films have been prepared by the “flash” evaporation method. The films exhibit carrier mobilities greater than 1000 cm2/Vs at thicknesses of about 1000 Å. Hall measurements at various temperatures have been made. The experimental results, i.e. Hall measurements and the dependence of the mobility on film thickness, are in good agreement with the theory of transport effects, which follows from the quasi‐discrete nature of energy spectrum in thin films.