bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of Alnico 8 by Mössbauer Spectroscopy
Authors: Makabov E. F. , Povttskii V. A. , Granovskii E. B. , Fridman A. A. 
Published: July 2007

AbstractThe 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

AbstractA 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

AbstractThermal 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

AbstractA 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

AbstractThe 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.
On Slow High Field Domains in Homogeneous Photoconductors
Authors: Döhler G. 
Published: July 2007

AbstractThe 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

AbstractThe 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

AbstractElectron 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

AbstractBy 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

AbstractA 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

AbstractAbsorption 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

AbstractThin 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

AbstractThe 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

AbstractA 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

AbstractFor 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

AbstractSupraleitende 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

AbstractElektronenmikroskopische 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

AbstractAnhand 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

AbstractA 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

AbstractThe 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.
Excitonic Effects in the Electro‐Absorption of Semiconductors
Authors: Enderlein R. 
Published: July 2007

AbstractThe 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

AbstractThe 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

AbstractAn 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

AbstractIn 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

AbstractThe 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

AbstractEmploying 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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.