bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermotransport and the Associated Isotope Effect in Solids
Authors: Lodding A.
Published: July 2007

If the same mechanisms governs self‐diffusion, electrotransport, and thermotransport, then the kinetic energy distribution factor of diffusion. ΔK, can be measured directly by isotope transport techniques (electro‐ or thermotransport), in solid metals as well as ionic salts. Under these conditions the results of the isotope thermal diffusion experiments can be interpreted in terms of activation energy parameters. However, in the only two solids in which isotope thermotransport has been measured so far, cubic Li2SO4 and Li metal, these simple conditions probably do not apply.
Low Temperature Internal Friction of Aluminum at 1 Hz
Authors: Routbort J. L. , Sack H. S.
Published: July 2007

The internal friction and shear modulus of single and polycrystals of Al were measured of 1 Hz from 4.2 to 300 °K as a function of the amount of deformation, temperature at deformation, and gamma irradiation. Two Bordoni peaks were found with activation energies of (0.16 ± 0.01)eV and (0.26 ± 0.03) eV, and attempt frequencies of 5 × 10(12 ± 0.6)s−1 and 3 × 10(14 ± 1.3) s−1, respectively. The low temperature peak has a single attempt frequency, but a distribution of activation energies, while the process contributing to the other peak involves a distribution of attempt frequencies, and possibly a single activation energy. Gamma irradiation at low temperature does not effect these peaks. The relaxation strengths of the processes are a function of temperature. The annealing behavior of the Bordoni and other peaks found after low temperature deformation was also studied.
Plasmon Satellites of Soft X‐Ray Spectra
Authors: Brouers F.
Published: July 2007

A theory of the intensity and shape of plasmon satellite bands in the soft X‐ray emission spectra of aluminium, magnesium and sodium is proposed. Based on the Bohm and Pines semi‐quantitative treatment of the electron gas, this theory is able to account very satisfactorily for the experimental data and provides a physical interpretation of the phenomenon. Because the electron undergoing the transition and the localized vacancy have opposite charges, their plasmon eigenfields partially cancel one another when the X‐ray transition occurs. This interference effect is not total because of the slight difference between the two plasmon field frequencies which arises from the relative motion of the vacancy and electron. This explains the occurrence and the weak intensity of the plasmon emission. The dispersion of the plasmon frequency provides an explanation of the profile of the plasmon satellites. Similar effects must occur when the electron‐positron annihilation in a metal is accompanied by the emission of a real plasmon.
Evaporation of As from GaAs
Authors: Roberts F. E.
Published: July 2007

Ambient vapour conditions sufficient to suppress evaporation from a volatile solid are derived for the case when solid and vapour are at different temperatures. From comparison with experiments on GaAs it is concluded that As2 plays a major part in arsenic evaporation from GaAs.
Theory of Plasmon Excitation in Thin Films by Electrons of Non‐Normal Incidence
Authors: Otto A.
Published: July 2007

Calculations of characteristic energy losses of electrons in thin dielectric foils are given for a) electrons with inclined incidence to the foil, b) electrons travelling parallel to the foil surface. Retardation is taken into account for case b) in the limit of very thick foils. For the special case in which the dielectric behaves as a free electron gas, excitation probabilities and dispersion relations are deduced for bulk and surface plasmons.
Spontaneous Recombination of Frenkel Pairs for Electron Irradiation
Authors: Dettmann K. , Leibfried G. , Schroeder K.
Published: July 2007

The damage rate for electron irradiation is calculated from the general equations for the spontaneous recombination of Frenkel pairs. The calculation uses the superposition approximation in which third order correlations are replaced by second order correlations. Comparison with the measurements of Dworschak et al. for 3 MeV electrons gives for copper an annealing volume, νa = 200 atomic volumes, and a fraction γ = 0.1 of interstitials, originally in unstable positions around their corresponding vacancies.
Paramagnetic Relaxation and Observation of a Phonon Bottleneck in Terbium Ethyl Sulfate
Authors: Kahle H.‐G. , Kalbfleisch H. , Stein K.
Published: July 2007

A pulse modulated magnetic field is used to study the paramagnetic relaxation in terbium ethyl sulphate. This method can be used to obtain two different types of disturbance of the thermal equilibrium between the spin‐system and the phonons. It is seen that there are different relaxation functions and different dependences of the measured (effective) relaxation time Teff on the magnitude of the initial disturbance for both of these types of disturbance. The experimental results are in good agreement with the theory of paramagnetic relaxation which includes the phonon bottleneck.
Quenched‐in Levels in p‐Type Silicon
Authors: Elstner L. , Kamprath W.
Published: July 2007

Hall effect measurements are described on heat treated and quenched p‐type silicon crystals. Donor centres appear at (Ev + 0.37) eV after this treatment. Introduction and annealing studies indicate that these centres are vacancy clusters. Similar investigations are made on electron irradiated samples.
Theory of Weakly Bound Bloch Electrons in a Magnetic Field. II. Asymptotic Approximation
Authors: Fischbeck H. J.
Published: July 2007

The Schrödinger equation of an electron in a weak two‐dimensional periodic potential and a homogeneous magnetic field is solved by an asymptotic approximation which is essentially a generalization of the WKB method to systems of ordinary differential equations. This approximation proves to be the mathematical substantiation of the Pippard network model of magnetic breakthrough.
Eine Verallgemeinerung der Korringa‐Kohn‐Rostoker‐Methode zur Berechnung von Einelektronenzuständen in Kristallen
Authors: Bross H. , Anthony K. H.
Published: July 2007

Im Rahmen der Einelektronennäherung wird ein Verfahren entwickelt, das mit Hilfe von Greenschen Funktionen die Elektronenzustände in idealen Kristallen zu berechnen gestattet. Gegenüber der von Korringa bzw. Kohn und Rostoker angegebenen Methode weist es folgende Vorteile auf: 1. Die Wellenfunktionen sind samt ihren ersten Ableitungen im ganzen Raum stetig. 2. Das Einelektronenpotential muß nur innerhalb einer um jedes Gitteratom gelegten Kugel sphärisch symmetrisch sein. Im Gebiet zwischen den Kugeln kann es beliebige Gestalt annehmen. 3, Es wird eine Greensche Funktion verwendet, die für alle Wellenvektoren definiert ist.
Die Interpretation des elektronenmikroskopischen Beugungskontrastes von Einschlüssen nahe einer kräftefreien Folienoberfläche
Authors: Chik K. P. , Wilkens M. , Rühle M.
Published: July 2007

Der elektronenmikroskopische Beugungskontrast von sphärischen Einschlüssen nahe einer kräftefreien Folienoberfläche wird berechnet und mit Hilfe der Theorie der modifizierten Bloch‐Wellen kritisch diskutiert. Es wird gezeigt, daß der sogenannte Schwarz‐Weiß‐Kontrast (S‐W‐Kontrast) auf zwei Ursachen beruht: „Interbandstreuung”︁ zwischen den modifizierten Bloch‐Wellen und „Randbedingungen”︁, denen die Elektronenwellen an den Folienoberflächen genügen müssen. In Übereinstimmung mit McIntyre und Brown [12] finden wir, daß bei Einschlüssen mit hinreichend starker Verzerrung der umgebenden Matrix die „Tiefenoszillationen”︁ des S‐W‐Kontrastes unterdrückt werden. Es wird gezeigt, daß dieser Effekt unmittelbar auf Besonderheiten des Verschiebungsfeldes eines Einschlusses in der Nähe einer kräftefreien Oberfläche zurückzuführen ist.
On the Dielectric Function of a Semiconductor in an External Electric Field
Authors: Enderlein R. , Keiper R.
Published: July 2007

The field‐induced change in the intraband and interband parts of the complex dielectric function is calculated for the various types of critical points. The field‐induced change in the plasma frequency has a quadratic dependence on the field. Limits of validity for the effective mass approximation are given. The influence of collisions on the field‐induced change of the interband part of the dielectric function is dealt with.
Influence of Oxygen Segregations in Silicon Single Crystals on the Halfwidth of the Double‐Crystal Rocking Curve of Thermal Neutrons
Authors: Eichhorn F. , Sippel D. , Kleinstück K.
Published: July 2007

Oxygen segregations in silicon crystals produced by the Czochralski method are shown to be arranged on “Wendelflächen” by using the Schwuttke model. The crystal lattice therefore contains an anisotropic distortion field. A study is made of the effect of this distortion on the half‐width of double‐crystal rocking curves for thermal neutrons.
The Mechanism of Diffusion in B.C.C. Transition Metals
Authors: Peart R. F. , Askill J.
Published: July 2007

A simple divacancy‐vacancy analysis has been applied to diffusion data in b.c.c. transition metals. Consideration of the divacancy contribution at high temperatures to diffusion coefficients determined with radioactive tracers is shown to be consistent with the nonlinear Arrhenius relationships for diffusion in V, Cr, β‐Ti and β‐Zr and with the corresponding linear relationships obtained for other b.c.c. metals.
Double Injection into CdS Single Crystals
Authors: Rohde H. J.
Published: July 2007

Simple reaction kinetic models are developed, to describe the dark conductivity of CdS‐type photoconductors. In addition to recombination centres, shallow electron and hole traps are considered. Double injection characteristics, developed in making use of a neutrality approximation, contain a threshold voltage Vth for double injection which is identical to that of the Lampert model [1]. For the case of weak population of the trapping states, the threshold voltage is followed by a j ∼ V2 law. At higher population a power law j ∼ Vn (n > 2) is expected. When the voltage passes some maximum voltage Vmax > Vth the characteristic joins that of the Lampert model. Measurements at different temperatures and electrode separations show good agreement with the theoretical results. It is shown that filling of trapping states by single carrier injection at the trapfilled‐limit voltage VTFL and field ionization of filled centres can be excluded from the interpretation of the experimental results.
Berechnung des Peierls‐Potentials im Diamantgitter mit Hilfe der Pseudopotentialmethode
Authors: Teichler H.
Published: July 2007

Es wird gezeigt, daß das Peierls‐Potential unter Berücksichtigung aller Paarwechselwirkungen zwischen den Atomen eines Kristalles durch die Fourier‐Transformierte des Wechselwirkungspotentials und der mit der Versetzung verbundenen Änderung des Strukturfaktors ausgedrückt werden kann. Zur Anwendung auf Schraubenversetzungen in Ge und Si wird das Verschiebungsfeld näherungsweise durch das Verschiebungsfeld einer Versetzung im anisotropen Kontinuum ersetzt. Das Wechselwirkungspotential zwischen den Atomen wird mit Hilfe der Pseudopotentialmethode bestimmt.
The Influence of s‐d Exchange on Relaxation of Magnons in Metals
Authors: Heinrich B. , Fraitová D. , Kamberský V.
Published: July 2007

A study is made of the relaxation of resonance spin waves by the s‐d exchange interaction. In contrast to previous work, the s‐electron spin relaxation is considered explicitly. Calculated relaxation times compare well with the results of recent experiments on iron.
Pressure Dependence of Elastic Constants of Cesium Halides
Authors: Chang Z. P. , Barsch G. R. , Miller D. L.
Published: July 2007

The single crystal elastic constants of CsCl, CsBr, and CsI have been measured at 13 °C as a function of hydrostatic pressure. The maximum pressure ranged from 2.3 to 6 kbar but was extended up to 10 kbar for two runs. The pressure dependence of the elastic constants was found to be linear within experimental error. The experimental results are compared with theoretical data by Nran'yan and Ghate. Also, the stability of the cesium chloride structure under pressure is discussed.
Band‐Filling Model for Injection Luminescence at Higher Temperatures
Authors: Eliseev P. G. , Krasilnikov A. I. , Manko M. A. , Pinsker I. Z.
Published: July 2007

An analysis is made of a simplified model of impurity band filling in heavily doped semiconductors at relatively high temperatures. The thermal energykTis considered to be comparable with the characteristic energy parameter of the impurity band which describes the rate of decay of the density of state into the gap. Results of the analysis are applied to injection luminescence and are verified by a spectral study of the radiation from a number of diffusion and epitaxial GaAs diodes. Degenerate and non‐degenerate cases of the impurity band filling may be distinguished. The shifting peak in the former case and fixed thermal excited one in the latter case are expected. An unexpected result of the analysis is that the line‐width in the non‐degenerate case is temperature independent. This result is supported by the measurements. When the energy distribution of the density of states of the impurity band is Gaussian the line‐width is directly related to the dispersion of the distribution. Observed values of this dispersion reach 35 meV in heavily doped samples and exhibit a correlation with the donor concentration. Some other features of the model are also discussed.
Impurity‐Induced Far‐Infrared Absorption in the Phonon Gap Regions of KI and KBr
Authors: Grisar R. G. J. , Reiners K. P. , Renk K. F. , Genzel L.
Published: July 2007

Measurements are made on doped KI and KBr using a far‐infrared grating spectrometer, which is briefly described. The absorption of KI:OD− at 4.3 °K exhibits localized vibrational and translational gap modes. An attempt to assign these modes is made by proposing a term scheme. Measurements of doped KBr between 2.5 and 80 °K confirm the boundaries of the acoustic‐optical gap as 96 cm−1 and 100 cm−1, respectively.
The Effects of Defect Doping on Low Temperature Neutron‐Irradiation Damage and Recovery in Aluminium and Platinum
Authors: Swanson M. L.
Published: July 2007

By means of residual electrical resistivity measurements, low temperature neutron‐irradiation damage was investigated in Al and Pt which were doped with various defects. It was found that the damage rate of Al at 1.8 °K was almost unchanged by the addition of 0.5% Mg, and furthermore, that the presence of this impurity suppressed the damage rate enhancement normally caused by deformation of high purity Al. Similar results were obtained for IS Al, which contains 0.35% Fe + Si. These results indicate that the effect of channeling on the damage rate of Al is small. The damage rate of Pt was affected little by deformation, but was enhanced approximately 12% for samples containing ≈︁ 10−4 quenched‐in vacancies. The stage I recovery of Pt was increased 30 to 50% by deformation or by quenched‐in vacancies. The results were compared with those of other investigations. It was concluded that most of the differences between heavy and light particle irradiations were caused by the greater importance of long‐range focused collision sequences in the former.
Pressure Coefficient of the Band Gap in Mg2Si, Mg2Ge, and Mg2Sn
Authors: Stella A. , Brothers A. D. , Hopkins R. H. , Lynch D. W.
Published: July 2007

The pressure deri vative of the band gap, (∂E/∂P)T, has been determined to be + 3 × 10−6 e Vbar−1 for Mg2Sn by measurements of the pressure derivative of the electrical conductivity. Similar measurements on Mg2Si and Mg2Ge were inconclusive, but estimates of this parameter were made from the shift of the optical obsorption edge with pressure. (∂E/∂P)T = (0 ± 0.5) × 10−6 e Vbar−1 for both compounds. The similarity of the coefficients for Mg2Si and Mg2Ge suggests that the symmetries of the band edges of both compounds are similar, while either the conduction band edge, the valence band edge, or both edges in Mg2Sn may have a different symmetry.
Study of Alnico 8 by Mössbauer Spectroscopy
Authors: Makabov E. F. , Povttskii V. A. , Granovskii E. B. , Fridman A. A.
Published: July 2007

The hard magnetic alloy “alnico 8” is investigated by Mössbauer spectroscopy. Two non‐equivalent positions are found for the Fe atoms in the hardened alloy. After tempering and a magnetic‐field heat treatment cycle (MFT) some of the Fe atoms are found to have a paramagnetic environment. The MFT has the effect of increasing the fraction of the Fe atoms which have such an environment and a maximum value of 7% is obtained for this fraction. The magnetic fields at the Fe57 nuclei are determined for various states of the alloy. The results are discussed together with the results of Mössbauer investigations of “alnico 5”.
Tunnel and Sehottky Current in Dielectric Thin Films Considering Film Thickness Fluctuations
Authors: Antula J.
Published: July 2007

A model for calculating tunnel and Schottky currents in thin dielectric films is introduced which considers film thickness fluctuations. The effective film thicknesses for film capacitance, and tunnel and Schottky currents, based on this model, are calculated and discussed.
Noncrystalline Structure and Electronic Conduction of Silicon Dioxide Films
Authors: Revesz A. G.
Published: July 2007

Thermal or anodic oxidation of silicon results in uniform noncrystalline SiO2 films but small crystallites may form at surface disturbances; these are pushed by the growing oxide to the outer surface. These films remain noncrystalline even after prolonged heat treatment. The stability behavior of SiO2, SiO, and Si3N4 films, and their relation to the corresponding crystalline modifications indicate that distinction should be made between glassy (vitreous), e.g. SiO2, and amorphous, e.g. SiO, noncrystalline materials. Electronic conduction plays a predominant role in the anodization mechanism of silicon. The oxide structure is changing during constant current oxidation; the oxidation efficiency and rate increase with thickness, but the apparent electronic conductivity is constant. Electron (hole) trapping during constant voltage anodization leads to a current that decreases with the reciprocal of time. Impedance measurements on MOS capacitors showed that sizable electronic conduction may occur in localized regions (“channels”). The density of these channels and the extent of conduction depends on the oxidation method and substrate orientation. A comparison between SiO2, GeO2, and Si3N4 shows that with increasing covalency and, especially, π‐character of the bond, the electronic conductivity and the ability to form noncrystalline structure increases. The π‐bonding is probably greater along a channel than in its surrounding.
Analysis of Dislocation Loops in Superlattices
Authors: Marcinkowski M. J. , Leamy H. J.
Published: July 2007

A detailed computer analysis of dislocation loop behavior in DO3 and B2 type superlattices has been performed. This analysis shows that DO3 superlattice dislocation nucleation most probably proceeds by the independent nucleation of four 1/2 a0 〈111〉 loops while the same process in B2 superlattices occurs by the independent nucleation of two such loops. Thus, superlattice dislocation loop nucleation requires a greater amount of energy in the DO3 case than does loop nucleation in a comparable B2 superlattice. These processes may be thermally activated so that at sufficiently low temperatures, e.g. 243 °K for Fe3Si (DO3), insufficient thermal energy is available and imperfect dislocations are nucleated. Thus, subsequent deformation in DO3 structures can only occur at stress levels commensurate with antiphase boundary production while deformation of B2 structures can occur at lower stresses since nucleation is much easier. — An analysis of equilibrium dislocation loop configurations in DO3 and B2 superlattices has also been carried out for various applied stresses. This analysis shows that the stress required to maintain a given radius of curvature in disordered, B2, and DO3 structures increases approximately in the ratio 1 : 2: 3. It has also been shown that the equilibrium spacing of a superdislocation loop pair increases with decreasing applied stress until, at some critical stress, the inner loop becomes unstable and collapses. The above processes have been shown to markedly effect the deformation behavior of ordered alloys.
Infrared Vibrational Absorption by U‐Centers in NaI
Authors: Bäuerle D. , Fritz B.
Published: July 2007

The local mode absorption in the infrared due to U‐centers in NaI has been measured. The ratio of local mode frequencies with H− and D− isotopes is 1.34. The main band shows a temperature‐dependent shift and broadening as well as a side band structure produced by local modeband mode coupling. The results are briefly discussed as arising from various anharmonic potential terms. There is no clear evidence from this experiment which shows directly the degree of perturbation of band‐mode phonons by the force constant change due to the defect.
Resistivity Studies of Electron Irradiated Iron
Authors: Neely H. H. , Keefer D. W.
Published: July 2007

Isochronal annealing studies of 1,3 MeV electron irradiated iron have been performed. Results indicate long range interstitial migration occurs in resistivity annealing substage IE (120 to 150 °K).
On Slow High Field Domains in Homogeneous Photoconductors
Authors: Döhler G.
Published: July 2007

The problem of slow high field domains in homogeneous photoconductors is discussed. Sufficient conditions for obtaining low domain velocities are derived. If the bulk conductivity decreases suddenly at a critical value of the electric field, then the approximation, based on a piecewise linearization of the equations, gives the velocity and the shape of the domain. A formula for the current flowing during domain movement is derived. The value of the amplitude of the oscillations is discussed.
On the Inherent Curvature of the Arrhenius Plot in Diffusion Experiments
Authors: Nowick A. S. , Dienes G. J.
Published: July 2007

The well known thermodynamic treatment of activated processes is used to determine the magnitude of inherent curvature of the Arrhenius plot, with specific application to the case of diffusion by means of a monovacancy mechanism. It is shown that the temperature dependence of the apparent activation energy Q is given by dQ/dT ≡ B = ΔCp where ΔCp is the difference in specific heat of the material containing an activated vacancy and of the perfect lattice. An estimate of B shows that |B|/R≦ 1.0 (where B is in molar units and R is the gas constant). On the other hand, available diffusion data for metals B‐values which are an order of magnitude higher. It is therefore concluded that the observed curvature is not due to an inherent effect, but to the existence of more than one mechanism of diffusion.
Conduction Electron Spin Resonance in Small Particles of Gold
Authors: Dupree R. , Fobwood C. T. , Asmith M. J.
Published: July 2007

Electron spin resonance has been observed in small particles of gold with a mean dia‐ meter of 30 Å. The resonance is attributed to conduction electrons in particles where the electron‐phonon interaction is severely inhibited. The mean g‐value is 2.26 ± 0.02 and the mean line width 200 G. A variation of line width with temperature has been observed and is explained tentatively in terms of the discreteness of the electron energy levels.
Low Temperature Conductivity of Ca‐Doped KCl Crystals Influenced by Segregation Processes
Authors: Fröhljch F. , Hensel G.
Published: July 2007

By conductivity measurements of Ca doped KCl crystals between 20 and 90 °C it is shown that the conductivity isotherms may be described by the association theory only for small Ca concentrations below 6 × 10−5 mole fraction Ca/KCl. The effect of the OH ions is given here in terms of characteristic deviations. For higher Ca concentrations the shape of the conductivity isotherms depends on the history of the crystals. By investigations of crystals with suitable thermal pretreatment it is shown that the shape of the isotherms, and especially the slow temporal decrease of the conductivity of quenched specimens, may be explained by precipitation processes of the Ca ions.
Mossbauer Effect in Complex Multicomponent Systems
Authors: Iosilevskii Ya. A.
Published: July 2007

A study is made of a number of low‐temperature results concerning the Debye‐Waller factor and the thermal shift of the Mössbauer line in solid solutions and in ideal multicomponent crystals. These do not depend in the explicit form on the concentration of the components or on the details of the microstructure and can be expressed in terms of other quantities (such as mass of an active atom and the Debye frequency of the system) which are estimated independently. The effective Debye frequencies are discussed.
The colour centre absorption of X‐Ray coloured alkaline earth fluoride crystals
Authors: Görlich P. , Karras H. , Symanowski Ch. , Ullmann P.
Published: July 2007

Absorption by colour centres (i. e. the Ψ‐centre comprising an anion vacancy with a trapped electron) is observed in pure alkaline earth fluoride crystals after subtractive coloration at temperatures of 300, 84, and 37 °K. Colorability increases with decreasing temperature and increasing cation radius of the crystal hosts. The coloration spectra of the CaF2 and SrF2 crystals are similar; they consist of a strong double band, called the Ψ‐band, a weak ultraviolet band, probably caused by hole imperfections, called Ω‐centres, and an increase in absorption at 200 nm (Ω‐centre: collective term for all hole imperfections occuring in alkine earth fluoride crystals [8]). The peak of the Ψ‐band occurs at 375 nm for CaF2 and at 434nm for SrF2. BaF2 crystals exhibit two different coloration spectra depending on whether they are coloured at room temperature or at lower temperatures. Both the coloration spectra of BaF2 are dissimilar to the type of spectrum observed for CaF2 and SrF2. On heating the CaF2 and SrF2 crystals, strong discoloration is only observed at relatively high temperatures (between 125 and 150 °K); on the other hand, coloration increased when it is performed at 37 instead of 84 °K. Saturation of the coloration of the BaF2 crystals takes place at 84 °K whereas their discoloration commences already between 85 and 100 °K. The discussion of the results considers special models and uses published results for additive coloration spectra, electron spin resonance and theoretical calculations.
The growth and defect structure of gold films formed on molybdenite in Ultra‐high vacuum
Authors: Stowell M. J. , Law T. J.
Published: July 2007

Thin films of gold have been grown epitaxially on molybdenite substrates under ultrahigh vacuum conditions. The topographic structures of these deposits differ only slightly from those formed in conventional high vacua [1], and the differences are attributed to enhanced surface self diffusion of the gold deposit. The defect structures of the films are similar to those formed in films grown in less clean vacua [2], and this shows that no fundamental changes occur in the mechanisms of defects production and mobility when vacuum environment is improved.
Annealing kinetics of voids and the Self‐diffusion coefficient in aluminum
Authors: Volin T. E. , Balluffi R. W.
Published: July 2007

The annealing kinetics of voids in 99.9999 wt% pure aluminum were studied over the temperature range 85 to 209 °C in thin specimens by transmission electron microscopy. The isothermal shrinkage of individual voids was measured and interpreted on the basis of a self‐diffusion annealing model. The self‐diffusion coefficient of aluminum, as determined from the data, was given by Ds = 0.176 exp (‐1.31 eV/kt) cm2s−1. The activation energy, Q = 1.31 eV, is significantly lower than the value Q = 1.48 eV determined by Lundy and Murdock at temperatures near the melting point in the only reported measurement by the radioactive tracer technique. Considerable evidence from a variety of sources is discussed which tends to support the present result.
A new variational ansatz in the polaron theory
Authors: Röseler J.
Published: July 2007

A new translational invariant variational statement is given, which is exact to the order α2 for weak coupling and which is in the limiting case of strong coupling regarding the polaron self‐energy not poorer as‐0.105 α2 h ω. In the limiting case of weak coupling the polaron mass, the contributions to the self‐energy due to the individual components of Fröhlich's Hamiltonian, and up to the order α2 the mean value of virtual phonons in the ground state are exactly calculated.
Space‐charge‐limited currents and high electric field effect in vitreous selenium films
Authors: Viščakas J. , Mačkus P. , Smilga A.
Published: July 2007

For vitreous selenium films, from 5 to 57 μm in thickness, dark steady‐state current—voltage characteristics are measured between 1 and 103V. The currents proportional to U2 d−3 can be interpreted in terms of space‐charge‐limited currents (SCLC) with a single trap level. A steep increase in current at the end of the square‐law region is not caused by trap filling but by field ionization. The mean value of the electric field at the cathode, at which the ionization current predominates over the SCLC is of the order of 1.3 × 107Vm−1. Restrictions imposed on SCLC by the field ionization of traps are discussed.
Der direkte Nachweis von Flußlinienbewegungen in stromdurchflossenen Supraleitern
Authors: Träuble H. , Essmann U.
Published: July 2007

Supraleitende Bleifolien mit einer Dicke d ≤ 0,05 mm zeigen unter der Wirkung eines transversalen Magnetfeldes eine magnetische Struktur, die aus Makroflußlinien mit ca. 50 Fluxoidquanten pro Flußlinie besteht. Schickt man durch die Folien einen hinreichend hohen Transportstrom senkrecht zur Feldrichtung, so bewegen sich die Flußlinien in diskreten Bahnen unter einem Hallwinkel α durch die Proben. Durch Versetzungen und Korngrenzen wird die Flußlinienbewegung erheblich beeinflußt.
Untersuchungen zur aktiven Kristallänge im Fließbereich neutronenbestrahlter Kupfereinkristalle. I. Die Ausbildung der Gleitbänder
Authors: Neuhäuser H.
Published: July 2007

Elektronenmikroskopische und kinematographische Untersuchungen zeigen, daß die Gleitbänder im Lüdersband neutronenbestrahlter Kupfereinkristalle aus einzelnen Gleitlamellen aufgebaut sind, die im Verlauf der Gleitbandausbildung mehr oder weniger rasch nacheinander entstehen. Die Abgleitung innerhalb der Lamellen verläuft in guter Näherung homogen und dauert nur kurze Zeit an (z. B. ≈ 10−1 s bei einer Verformungsgeschwindigkeit ≈ = 10−3 mm/s und Zimmertemperatur). Struktur und Ausbildung der Gleitbänder in Abhängigkeit von Dehngeschwindigkeit, Temperatur und Bestrahlungsdosis werden qualitativ erklärt durch ein Wechselspiel zwischen Schneid‐ und Quergleitprozessen der Gleitversetzungen.
Zur Phänomenologie der Leuchtverteilungen in elektrolumineszierenden, hexagonalen ZnS‐Kristallen
Authors: Kümmel U. , Zollfrank G.
Published: July 2007

Anhand von Mikrophotographien wird die Leuchtverteilung von elektrolumineszierenden ZnS‐Kristallen beschrieben und mit der strukturbedingten Schichtung dieser Kristalle in Verbindung gebracht. Elektrolumineszenz im Kristallinnern tritt nur dann auf, wenn sich ein Stromfaden bzw. ein Netzwerk von Stromfäden ausbilden kann. Diese Stromfäden, in denen die Elektrolumineszenz entsteht, sind durch die Versetzungen des Gitters vorgezeichnet. Zu ihrer endgültigen Ausbildung ist eine feldbedingte Veränderung zwischen den Teilabschnitten einer Versetzungslinie notwendig. Nicht alle lumineszenzfähigen, durch Versetzungslinien vorgezeichneten Gebiete werden elektrisch angeregt. Es erfolgt insofern eine Auswahl unter ihnen, als ihre Elektrolumineszenz‐Intensität durch ihre Zeitkonstante (RC‐Wert). ihre Lage relativ zur Richtung des elektrischen Feldes und ihre Entfernung zu den benachbarten Stromfäden bestimmt wird.
Model potential for systems with two valence electrons
Authors: Logatchov Yu. A.
Published: July 2007

A pseudo‐potential approach is developed for complex systems having two valence electrons. The dependence of the parameters of the model potential operator VM upon the energy and orbital quantum number of the valence electron is shown to be important in the problems considered. The method gives the excited states of atoms and impurity centres and the interaction of an electron in an impurity ion with the regular ions of the lattice. The optical excitation energy of luminescence centres obtained by a variational method is in good agreement with empirical data. The work can be regarded as a basis for including the correlation of extra electrons in calculations on impurities.
Ferromagnetic Resonance Measurements of Magnesium–Manganese Ferrite Films
Authors: Macháčková J.
Published: July 2007

The aim of this work is to prepare ferrite films with a narrow FMR absorption line and to determine some magnetic parameters of polycrystalline and single crystal films and their changes with temperature. The influence of thermal treatment on the absorption line half width and on the values of the external static resonance field H is investigated. The excitation of magnetostatic modes is observed for perpendicular orientation of H and the film. The changes of these modes after polishing the surfaces of the films are investigated.
The Temperature Dependence of the Paramagnetic Susceptibility of NiI Boracite
Authors: Heinrich B. , Zítková J. , Kaczér J.
Published: July 2007

The decrease of the paramagnetic susceptibility in NiI boracite with decreasing temperature is explained taking into account the thermally excited paramagnetism of the sublattice of the Ni2+ ions.
Excitonic Effects in the Electro‐Absorption of Semiconductors
Authors: Enderlein R.
Published: July 2007

The effect of electron–hole interaction (excitonic effects) on the electro‐absorption in semiconductors is investigated. The effective time‐dependent Schrödinger equation of the problem is solved exactly for x → 0. Explicit expressions for the shape of the exciton lines in the electric field are given. The field‐induced change of the interband absorption is discussed in the limiting cases of weak and strong electron‐hole interaction.
Nonlinear Polarisation of an Impurity Crystal
Authors: Trifonov E. D. , Troshin A. S.
Published: July 2007

The polarization in a crystal containing impurities which is caused by the interaction with an electromagnetic field is given in terms of the Fourier transforms of the first‐order emission and absorption spectra due to the impurities. The results are obtained by means of the time‐dependent perturbation theory using the diagram technique. It is also shown that electron density matrix of the impurities satisfies the equations with two relaxation constants γ and Γ if the first‐order spectra are supposed to be of Lorentzian type.
Die Bestimmung der Austrittstiefe von Photoelektronen in Caesium–Antimon‐Schichten
Authors: Hirschberg K. , Deutscher K.
Published: July 2007

An Halbleiterkathoden vom Typ Cs3Sb wurden im sichtbaren Spektralbereich die optischen Konstanten, die Schichtdicke und der Photostrom gemessen. Die aus den optischen Messungen berechnete Energieverteilung in der Schicht und die Transportfunktion für Elektronen bestimmen den emittierten Photostrom. Die Größe der Austrittstiefe der Photoelektronen—Parameter der Transportfunktion—wird mit dem Quotientenverfahren ermittelt. Im untersuchten Spektralbereich von 440 bis 620 nm hat die Austrittstiefe einen Wert von 15 nm.
Determination of the Energy of Conduction States in Anthracene Crystals by Photoemission of Electrons from Sodium
Authors: Vaubel G. , Baessler H.
Published: July 2007

In a previous paper the photo‐emission of electrons from evaporated Na and Cs cathodes into anthracene crystals has been studied. Using this technique the existence of an upper conduction band has been established. In this paper the photo‐emission into free electron states above the ionization level of the anthracene crystal is observed. The threshold energy of 2.72 eV can be interpreted as the sum of the vacuum work function of Na and the potential of a dipole layer formed by charge‐transfer complexes at the Na–anthracene interface, which can act as a source for electron injection after optical excitation, too. From the knowledge of this energy and the threshold energies for photo‐emission into the first and second conduction band the energy differences between the bottoms of both conduction bands and the free electron level can be deduced. Values of 1.72 and 1.27 eV, respectively, are obtained. The energetic separations to the valence band are 3.93 and 4.38 eV, respectively.
One‐Band One‐Site Model for Crystal Imperfections
Authors: Fowler W. B.
Published: July 2007

The one‐band one‐site model for crystal imperfections, introduced by Koster and Slater, is critically examined. A simple improvement scheme, which is equivalent to a many‐band one‐site model, is proposed. These ideas are tested on a case for which exact solutions are known, namely, a one‐dimensional potential well. It is found that the one‐band one‐site approximation gives rather unreliable results, in general, and that the improvement scheme is indeed an improvement, converging to the exact answer as the one‐site approximation becomes exact.
Zener Relaxation in Silver Solid Solutions
Authors: Williams G. P. , Turner T. J.
Published: July 2007

Employing a torsion pendulum and elastic‐after‐effect apparatus, activation energies for Zener relaxation in 10.8 and 18.1 at% In in Ag were found to be 35.1 and 33.4 kcal/mol respectively. These results and the diffusion data of Schoen were used in conjunction with a theory taking into consideration pair dissociation as well as reorientation. Activation energies for atomic reorientation of 34.5 and 31.0 kcal/mol respectively were deduced for these same concentrations. Zener relaxation was also observed in 8.1 at% Sn in Ag and 6.3 at% Sb in Ag for which the activation energies were measured to be 31.5 and 32.5 kcal/mol respectively.
Two‐Electron Correlation in Impurity Centres in Model Potential Approximation
Authors: Logatchov Yu. A.
Published: July 2007

The energy states of impurity centres are calculated including the correlation of optical electrons. It is shown that the correlation energy Ecor for the state 1S0 of the luminescence centre in KCl(Tl) is about 3% of the energy of two optical electrons; for the state 3P1 Ecos is negligible. Taking the two‐electron correlation into account, the transition energy 1S0 → 3P1 is calculated for KCl(Tl).
Electron Injection into a p‐Type Semiconductor
Authors: Roberts G. G.
Published: July 2007

The problem of minority carrier space charge injection is considered. Diffusion effects are included in the theory and numerical results are presented for electron injection into a p‐type semiconductor. The resulting current‐voltage characteristic shows ohmic behaviour preceding a region in which the current density becomes proportional to the square root of the applied voltage and independent of the specimen thickness. Experimental d.c. characteristics of single crystal trigonal selenium with evaporated indium electrodes show a sub‐ohmic behaviour in accord with the theory mentioned above.
The Position of the Dislocation Acceptor Level in n‐Type Ge
Authors: van Weeren J. H. P. , Koopmans G. , Blok J.
Published: July 2007

The Hall coefficient of plastically bent n‐type Ge is measured between 77 and 280°K. The dislocation acceptor level is found to lie 0.35 eV below the conduction band. From the experimental results we conclude that the electrons accepted by the dislocation are uniformly distributed along the dislocation.
The Effect of Pressure on the Electron Effective Mass in InSb
Authors: Akselrod M. M. , Demchuk K. M. , Tsidilkovski I. M. , Broyda E. L. , Rodionov K. P.
Published: July 2007

The effect of hydrostatic pressure P up to 1.05 × 104 atm on the electron effective mass m* in samples of InSb with electron densites of n = 2 × 1014 to 8.3 × 1016 cm−3 at T ≈ 100°K is studied. The effective mass is determined from both the magnetophonon (MP) oscillations of the longitudinal and transverse magnetoresistance and the Hall effect and thermo‐electric power in strong magnetic fields. The obtained dependence of m*(P) agrees with Kane's theory.
On the Experimental Observation of Small Polarons in Semiconductors
Authors: Klinger M. I.
Published: July 2007

An analysis is made of experimental methods for observing small‐polaron conductivity in order to study the properties of small polarons. Special attention is paid to infrared absorption measurements. Some recent data on TiO2 are discussed.
A Step Annealing Procedure for the Determination of Diffusion Coefficients in Metals by the Resistometric Method‐Application to the Diffusion of Cu in Al
Authors: Ceresara S.
Published: July 2007

A simple experimental procedure is described which enables the resistometric determination of diffusion coefficients in metals by the employment of only one diffusion sample. Results obtained for diffusion of Cu in Al well compare with data reported in the literature.
On the Theory of Shallow Impurity States
Authors: Sak J.
Published: July 2007

A theoretical investigation is made of the shallow states of an impurity interacting weakly with polar phonons. An effective mass equation is found containing besides usual terms corrections including the renormalization of the electron mass, deviations from the parabolic dispersion law (due to phonons), and a contact term arising from the interaction of the electron with the fluctuations of the phonon field. Physical interpretation of the contact interaction is given. Analogy between a polaron and an electronic polaron is recalled to draw some conclusions concerning electron‐electron correlation. The shift of the lowest energy level of a hydrogen‐like impurity is calculated.
Twist Boundaries and Electroluminescence
Authors: Daniels B. K. , Meadowcroft D. B.
Published: July 2007

Twist boundaries have been introduced into needle crystals of zinc sulphide and their effects on electroluminescence investigated. Because of the very small size of the crystals a special experimental technique was developed. Within the limit of accuracy of the experimental measurements no effects of the twist boundaries could be detected. This result is examined from several points of view and further possible experiments are suggested.
The Influence of Structure on the Electroluminescence of Zinc Sulphide
Authors: Alfrey G. F. , Meadowcroft D. B.
Published: July 2007

Electroluminescence has been measured from small regions within vapour‐grown ZnS crystals, and can be correlated with the crystal structure of the regions, since impurity content and other factors should be constant in these conditions. The emission is found to be lower for disordered structures, in contrast to previous work on phosphors. It is suggested that, at the low activator concentrations prevailing, decoration of dislocations does not occur, so that processes depending on conducting inclusions are inoperative. Scattering at the defects will, on the other hand, reduce the efficiency of impact excitation.
Electrical and Optical Properties of Sputtered In2O3 films. I. Electrical Properties and Intrinsic Absorption
Authors: Müller H. K.
Published: July 2007

Thin films of n‐conducting In2O3 are prepared by reactive sputtering. The concentration of conduction electrons is changed by a heat treatment between ne = 1017 and 1020 cm−3 (T = 300°K). Concentration and temperature dependence of the electron mobility indicate an intense scattering at charged imperfection centres which are due to a considerable intrinsic lattice disorder. The intrinsic absorption is also influenced by this disorder.
Thermoelectric Force of hot Carriers
Authors: Pozhela J. K. , Repshas K. K.
Published: July 2007

The thermo‐electric power of hot carriers UT due to a high electric field E is investigated. Two cases are considered: 1) weak electric field (E ≦ 103 V/cm) and 2) high electric field (E ≧ 103 V/cm). The theory is developed for both cases in the approximation of the isotropic mass and quasi‐elastic scattering. Dc pulse measurements on n‐type germanium in a weak electric field yield a quadratic dependence of UT on the electric field strength. The experimental results are found to be in a satisfactory agreement with theory. In high electric fields the microwave technique is used. It is concluded that the energy relaxation for high‐energy electrons in n‐Ge is determined mainly by acoustical modes.
The Theory of Shallow F‐Centres
Authors: Perlin Yu. E. , Gifeisman Sh. N.
Published: July 2007

A theory of hydrogen‐like impurity centres in ionic crystals in the presence of an external magnetic or electric field is developed. The coupling to longitudinal optical phonons is taken into account, and the results are valid for arbitrary interaction strength. Feynmans path‐integral representation for the partition function of the phonon‐impurity system and a variational principle connected with a quadratic trial Lagrangian are used. A simple expression for the bound polaron ground‐state energy with a single variational parameter is derived. Formulae for the magnetic and electric susceptibilities are obtained. The electron‐phonon coupling reduces essentially these susceptibilities in comparison with the results of a hydrogenic model.
On the Theory of Thermogalvanomagnetic Phenomena in Semiconductors at High Magnetic Fields
Authors: Kalashnikov V. P. , Zlobin A. M.
Published: July 2007

The transverse charge and heat flows of conduction electrons interacting with optical phonons at high magnetic fields are calculated. Explicit expressions for the diagonal elements of transport coefficients are derived taking into account the two‐stage mechanism of electron‐phonon scattering at low temperatures. The temperature and field dependences of these coefficients are obtained for the various cases.
Tensile Behavior upon Ordering of Ni3Fe Single Crystals
Authors: Victoria M. , Vidoz A. E.
Published: July 2007

The tensile properties of ordered and disordered Ni3Fe single crystals have been investigated. Also, polycrystalline specimens have been tested to show the influence of grain size on the deformation characteristics of Ni3Fe. Measurements have been made to determine the influence of parameters such as the initial orientation of the tensile axis of single crystals, the ordered domain size, and the test temperature on the mechanical properties of Ni3Fe. Tensile axis reorientation during deformation was followed with X‐ray techniques. It was found that in ordered single crystals, the measured tensile axis rotation agrees well with the calculated values if one activated glide system is assumed. The influence of secondary slip on the tensile characteristics of ordered crystals was determined by using specimens oriented for multiple glide. It is demonstrated that the work hardening rate increases with the occurrence of secondary slip. The strain‐aging phenomena shown previously in polycrystalline Ni3Fe was found to occur also in single crystals. The nature of the observed effects in ordered Ni3Fe is interpreted in terms of the antiphase boundary tube mechanism.
On the Work Hardening of Superstructures
Authors: Vidoz A. E.
Published: July 2007

The mechanism for the work hardening of superstructures proposed by Vidoz and Brown is modified. It is shown that this model explains the experimental results even when only a very small increase in the forest density, possibly too small to be observed experimentally, takes place during deformation. It is suggested that this small contribution of secondary slip may be due to a latent hardening effect. Analytical expressions for the stress to move primary and conjugate dislocation in a crystal are derived. The discussion shows that the antiphase boundary tube mechanism can explain most of the available experimental results.