bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interstitial Ordering of Carbon in Tantalum
Authors: Villagrana R. E. , Thomas G. 
Published: July 2007

AbstractThe effect of interstitial carbon on the structure of tantalum was investigated by transmission electron microscopy and diffraction. Interstitial ordering was found, and the ordered structure was determined from computation and comparison with electron diffraction data. The superlattice structure is tetragonal, with a c/a ratio of 1.128, and an ideal composition of Ta64C. Since the superlattice was determined from thin foils, it was necessary to compare the thin foil results with bulk specimens, alloyed to correspond to Ta64C. Microscopic examination of bulk specimens showed many domain boundaries, separating regions in which the tetragonality associated with ordering was oriented in different directions. An analysis of these domain boundaries indicates that there are three possible types: coherent, semicoherent, and antiphase.
Grüneisen Parameter for Long Wavelength Optical Modes in Ionic Crystals
Authors: Mitra S. S. 
Published: July 2007

AbstractThe Grüneisen parameter, γi for a normal mode of a crystal may be determined from the temperature or pressure coefficient of the normal mode frequency if it is assumed that the mode frequency is only a function of volume. γt for the zone center transverse optical mode frequency of RbI is obtained from its temperature dependent infrared spectrum. Expressions for γt and γl for the T.O. and L.O. modes at k ≈ 0 are derived from the Born and Huang theory using the rigid ion approximation.
Electron Emission Spectroscopy of Alkali Halides
Authors: Petrescu P. 
Published: July 2007

AbstractThe development of techniques for the study of photoemission from colored ionic crystals have led to a new method for measuring energy levels of electrons trapped in the crystal lattice. Some particular aspects of electron emission spectra (EES) from KCl, CsCl, and RbBr which are due to the Joshi effect or the other perturbing agents are explained. Characteristic EES for the Li, Na, K, Rb, and Cs halides, obtained by this method, are described. The values of λmax are compared with those predicted theoretically by Ivey or obtained by optical spectroscopy. The electron transfer between the F and M levels in potassium fluoride is analyzed.
Zur Analyse der Aktivierungsenergien der elektrischen Leitfähigkeit und der thermoelektrischen Kraft in Magnesiumeisen‐Ferriten
Authors: Schröder H. 
Published: July 2007

AbstractAn stöchiometrischen, polykristallinen Magnesiumeisen‐Mischferriten variablen Fe2+‐ Gehaltes werden bei verschiedenen Sauerstoffpartialdrucken Temperaturmessungen der elektrischen Leitfähigkeit und der thermoelektrischen Kraft ausgeführt. Die experimentell erhaltenen Kurven stehen bei nicht zu hohen Fe2+‐Gehalten in guter Übereinstimmung mit dem Elektronen‐Sprungmodell. Die Gegenüberstellung der Aktivierungsenergien der Leitfähigkeit und Thermokraft führt zu einer einfachen empirischen Beziehung. Aus der thermogravimetrisch ermittelten thermischen Sauerstoffdissoziation und den Tieftemperaturparametern des Systems wird das Hochtemperaturverhalten für eine bestimmte Ausgangszusammensetzung berechnet und mit dem Experiment verglichen.
Atomic Displacement Cross Sections in Copper for Anisotropic Threshold Energy
Authors: Wollenberger H. , Wurm J. 
Published: July 2007

AbstractEarlier theoretical investigations on models of α‐iron [3] and copper [7] give a highly anisotropic displacement threshold energy, especially near the main crystal axes. In this paper total cross sections for atomic displacements by low energy electrons (E < 0.5 Me V) are calculated with respect to various anisotropic threshold energies. In general, a minimum of the threshold energy near a crystal axis leads to “sub‐threshold” events, as found experimentally by Bauer and Sosin. The cross sections derived from experimental measurements have to be corrected to take account of the effect of the energy loss and the multiple scattering of the electrons before they may be compared with calculated values. The correction method is described and the values from the Bauer and Sosin experiment given. By fitting the experimental data, the angular‐dependent threshold energy is calculated near the 〈110〉‐direction in copper assuming the residual resistivity increase to be 2.5 μΩ cm/at.% Frenkel pairs. The threshold energy minimum obtained by this method should be important as regards the production of correlated replacement collisions.
Electronic Properties of Surface Layers of Silver Chloride
Authors: Snavely B. A. 
Published: July 2007

AbstractPhotoconductivity and luminescence produced by 0.2 μs X‐ray pulses, and thermally stimulated currents were measured between 80 and 260 °K. The electron schubweg is controlled by traps, some of which (in excess of 1015 cm−3) are deep and are destroyed by oxygen. The probability for radiative recombination is small compared to that for trapping. The mobility in oxygen doped crystals is the same in the surface as in the bulk. Anomalies in the temperature dependence of the mobility are attributed to trapping and re‐emission.
Imperfections in Copper‐Silicon Filings
Authors: Rao P. Rama , Anantharaman T. R. 
Published: July 2007

AbstractDetailed X‐ray line‐broadening studies are made on deformed filings of Cu96Si4, Cu92Si8, Cu90Si10, and Cu89Si11 alloys. The f.c.c. deformation fault parameters in fresh filings of the first three alloys, in each case of two different grain sizes, are determined by the Paterson method. Stacking‐fault contributions to the observed diffraction broadening are eliminated by a procedure suggested by Christian and Spreadborough, and the domain size and lattice strain effects are separated by single line Fourier analysis. The fresh filings of the two‐phase Cu89Si11 alloy show only the faulted h.c.p. structure, the f.c.c. phase having disappeared during deformation by filing. The fault parameter, domain size, and lattice strain values in the strain‐induced h.c.p. phase are also estimated.
Energy Gap Determination in Semiconductors by Electric‐Field‐Modulated Optical Absorption
Authors: Frova A. , Penchina C. M. 
Published: July 2007

AbstractA new technique is described for determining the band gap in semiconductors from measurements of the electric‐field‐modulated absorption of light (Franz‐Keldysh effect). This method is tc some extent more convenient than previous ones since it permits the use of rather thick samples. Yet, the precision is about as high as that achieved by other techniques. Experiments using this technique have been carried out in germanium. The direct energy gap is found to be 0.7990 ± 0.0005 eV at 305 °K and 0.8807 ± 0.0010 eV at 89 °K, in excellent agreement with the values reported by other authors.
Interaction of Magnetoplasma Waves with Spin Waves in a Transverse Magnetic Field
Authors: Mendelson K. S. , Spector H. N. 
Published: July 2007

AbstractThe interaction of magnetoplasma waves and spin waves in bulk ferromagnetic materials has been investigated for the case in which the direction of propagation is perpendicular to the static magnetic induction. For this geometry there are two types of magnetoplasma waves, but only one of them interacts with the spin waves. This one is a transverse plasma wave that propagates at frequencies above the plasma frequency. At wave numbers for which the interaction is a maximum, the modes cannot be identified as pure plasma or pure spin waves. The interaction can only be observed in materials in which the plasma frequency is less than the cyclotron frequency. Therefore, the interaction cannot be seen in metals, but it might be possible to obtain the interaction in a ferromagnetic semiconductor.
The Use of Directional Freezing of the Melt for the Preparation of Large Bismuth Single Crystals
Authors: Bednarski S. 
Published: July 2007

AbstractDirectional freezing is used for the preparation of large single crystals of bismuth. The diameter of cylindrical crystals obtained by this technique is 75 mm and the length 180 mm; the average mosaic spread is about 10 minutes of arc. The technique described may be applied to obtain single crystals of certain other materials which increase their volume during the process of solidification.
Elektrische Schwingungen in dünnen Schichten aus hexagonalem Selen
Authors: Polke M. , Hasler K. 
Published: July 2007

AbstractAn Aufdampfschichten aus hexagonalem Selen wurden bei angelegter Gleichspannung Schwingungen des elektrischen Stromes beobachtet, wenn die Probe mit Gleichlicht bestrahlt wurde. Die Ortsabhängigkeit des Potentials bei verschiedenen Bestrahlungsstärken und Raumtemperatur zeigte, daß mit dem Einsetzen der Schwingungen das Auftreten einer kritischen hohen Feldstärke vor der Anode verbunden war. Die Abhängigkeit der Schwingungsamplitude und der Schwingungsfrequenz von der angelegten Gleichspannung, der Temperatur, der Bestrahlungsstärke und der Wellenlänge des anregenden Lichts ergaben stets ein ähnliches Verhalten wie die entsprechenden Abhängigkeiten des Gleichstroms [1].
On the Mechanism of Ionization Processes in Silicon Carbide Occurring at High Electric Fields
Authors: Vereshchagin I. K. , Kirichuk A. S. 
Published: July 2007

AbstractElectric, photoelectric, and luminescent properties of carborundum‐crystal rectifying contacts are studied in the region just below breakdown of the current‐voltage characteristics. At reverse voltages above 4 V a multiplication of the optically generated carriers is observed in the region of the crystal barrier. A rapid rise in the dark current and the intensity of light emission together with an increase of voltage on the barrier, are also connected with impact ionization of the lattice. The ionization coefficient is of order 104 cm−1 with a field strength of approximately 4 × 105 V/cm.
Determination of Parameters of the Rotational Dynamics of the Groups NH4 in NH4ClO4 and H3O in H3OClO4 by Inelastic Scattering of Neutrons
Authors: Janik J. M. , Janik J. A. , Bajorek A. , Parliňski K. 
Published: July 2007

AbstractMeasurements of inelastic neutron scattering in NH4ClO4 and H3OClO4 are made from liquid nitrogen to room temperature. The absence of peaks in the scattering spectrum of NH4ClO4 suggests that the NH4 groups have rotational freedom. In the scattering spectrum of H3OClO4 a peak is observed at 0.062 eV which is considered to be due to hindered rotations of the H3O group.
Tunnelling and Capture in Ge Tunnel Junctions Doped with Ni
Authors: Constantinescu C. , Dolocan V. 
Published: July 2007

AbstractThe tunnel transitions and capture processes in Ni doped Ge tunnel junctions are investigated. From a comparison of the experimental values for excess current with the theory of tunnelling and capture, the capture cross sections of multi‐charged Ni centres in Ge are determined at 77 °K. Capture cross sections for electrons and holes by negatively charged Ni centres, and for electrons by neutral Ni centres, are found. The values agree satisfactory with those obtained from recombination studies.
Zum Streumechanismus von Stromträgern in Tellur‐dotiertem Galliumphosphid
Authors: Nasledov D. N. , Negreskul V. V. , Radautsan S. I. , Slobodchikov S. V. 
Published: July 2007

AbstractEs wurde die Beweglichkeit der Stomträger in Tellurdotierten GaP‐Einkristallen untersucht. Aus der Temperaturabhängigkeit des Hallkoeffizienten wurde die Ionisierungsenergie des Donatorniveaus zu etwa 0,11 eV bestimmt. Eine Analyse der möglichen Streumechanismen zeigt, daß die Streuung an polaren optischen Gitterschwingungen der dominierende Streumechanismus für die Elektronen ist. Die Beweglichkeit, die unter Berücksichtigung dieses Streumechanismus berechnet wurde, stimmt in der Größenordnung und in der Temperaturabhängigkeit gut mit den experimentellen Ergebnissen überein. Ein anderer wichtiger Streumechanismus ist wahrscheinlich bei tiefen Temperaturen die Streuung an neutralen Störstellen und an Raumladungsgebieten.
Thermodynamic Green's Function Approach to Impurity Conduction. II. ac Conduction
Authors: Gosar P. 
Published: July 2007

AbstractThe thermodynamic Green's function method is applied to the problem of ac impurity conduction in semiconductors. Both direct and indirect photon absorption processes are studied. A special technique is devised for the conctruction and calculation of the diagrams for the auto‐correlation function of the dipole moment operator. New results for the direct photon absorption conductivity are presented.
F‐Aggregate Center Formation at Low Temperatures in KCl
Authors: Sonder E. , Sibley W. A. 
Published: July 2007

AbstractMeasurements of the F‐center concentration, nF, and M‐center concentration, nM, for KCl samples irradiated with 1.5 MeV electrons at low temperatures show that the ratio nM/nF2 for electron irradiation is only one‐half that found previously for X‐ray irradiated crystals. The electron results are in appreciably better agreement with the value to be expected from a statistical model and an M‐band oscillator strength obtained by optical bleaching techniques. The discrepancy between the electron irradiation and X‐ray irradiation results is discussed and it is concluded that the statistical model, according to which an M‐center appears whenever two F‐centers are produced at adjacent sites, may not be adequate to describe F‐ and M‐center introduction at low temperature.
The Crystal Structure of Evaporated Gold Films
Authors: Pashley D. W. , Stowell M. J. , Law T. J. 
Published: July 2007

AbstractThe crystal and defect structure of polycristalline vapour‐deposited gold films has been examined by transmission and reflection electron diffraction. Accurate measurements have shown conclusively that extra differaction rings in transmission electron diffraction patterns arise by double diffraction across twin boundaries and not from a hexagonal close packed phase of gold, as has recently been suggested by several authors. The double diffraction rings in transmission patterns from [111] textured specimens arise mainly from crystals which are twinned about the texture axis. A comparison is made between transmission and reflection patterns from these crystals and the advantages of the transmission technique for this type of investigations are emphasized.
Tensile Kinking in Single Crystals of Cadmium
Authors: Blasdale K. C. A. , King R. 
Published: July 2007

AbstractLarge numbers of kinks form in single crystal specimens of certain samples of high purity cadmium on extension. The kinks appear at random along the length of the specimen during extension and no correlation with observable surface features or accidental damage has been found. The variation of kinking with purity, temperature and rate of strain has been examined. Kinking decreases with increase of impurity; this may be an indirect effect due to change of flow stress with impurity. The maximum kinking tendency is observed at temperatures near 20 °C. It is suggested that kinks form as a result of the holding up of slip dislocations at a dislocation array.
The Stability and Line Tension of a General Dislocation Loop in an Isotropic Medium
Authors: de Chatel P. , Kovács I. 
Published: July 2007

AbstractThe equilibrium condition of a general dislocation loop in an isotropic medium is deduced by a variational procedure. It is found that the forces due to the external and self‐stress (defined by Brown [5]) must cancel each other at any line element of the loop. This leads to a formula giving the line tension in terms of line integrals. It is shown, that the generally accepted formula T = E + d2E/dϑ2 is only applicable in the limiting case of nearly straight dislocations.
Spontane Rekombination von Frenkelpaaren
Authors: Dettmann K. 
Published: July 2007

AbstractEs werden allgemeine Gleichungen abgeleitet, die die spontane Rekombination von Frenkelpaaren bei Neutronen‐ und Elektronenbestrahlung beschreiben. Die Gleichungen werden in der Superpositionsnäherung gelöst, in der Dichten 3. Ordnung durch Produkte von Dichten 2. Ordnung ersetzt werden. Die einfachen Defektdichten werden in Abhängigkeit von der Zwischengitteratom‐Leerstellenkorrelation bei der Erzeugung berechnet. Im Fall der Elektronenbestrahlung wird nur die stationäre Dichte diskutiert.
Ferromagnetische Eigenschaften hexagonaler Kobalt‐Einkristalle
Authors: Träuble H. , Boser O. , Kronmüller H. , Seeger A. 
Published: July 2007

AbstractAn stabförmigen hexagonalen Kobalt‐Einkristallen wurden die Anfangssuszeptibilität χa und die Koerzitivfeldstärke Hc im Temperaturintervall zwischen 90 und 680 °K gemessen und die Verformungsabhängigkeit dieser Kenngrößen untersucht. Mit Hilfe der Bittertechnik wurde das Verhalten der Bereichsstruktur bei Raumtemperatur in Abhängigkeit vom Feld und der plastischen Verformung studiert. Infolge der unterschiedlichen Temperaturabhängigkeit der Kristallanisotropiekonstanten K1 und K2 von Kobalt gibt es drei Temperaturintervalle mit verschiedenartigen magnetischen Vorzugsrichtungen. Dadurch wird die Temperaturabhängigkeit von χa, Hc und der Bereichsstruktur weitgehend bestimmt.
Hysteresis Loops in the Microstrain Region
Authors: Lukáš P. , Klesnil M. 
Published: July 2007

AbstractPrevious papers concerning the hysteresis loops in the microstrain region have shown disagreement regarding the conditions under which closed hysteresis loops can be observed. The present paper shows that the explanation of this matter lies in the experimental procedure rather than in the type of material used. An investigation is also made of the physical meaning of the derivative of the dependence of hysteresis loop area on strain amplitude.
Hall Mobility of Slow Electrons in AgCl and the Effects of Crystal Purity
Authors: Masumi T. , Ahrenkiel R. K. , Brown F. C. 
Published: July 2007

AbstractThe mobility of carriers in AgCl was investigated over the temperature range 4 to 100 °K by a photo‐Hall technique. The Hall mobility of slow electrons is shown to be very dependent upon sample purity at low temperatures. Mobilities in excess of 30000 cm2/Vs were obtained in very high purity zone refined specimens. Special attention was given to the lattice scattering range of mobility above 40 °K in the pure crystals. Hall and drift mobility values for electrons are in reasonable agreement. Although the optical phonon scattering appears to dominate, there is an evidence that the Debye temperature is somewhat lower than expected. It is suggested that this might be due to a finite spread in the long wavelength longitudinal optical frequency. It is believed that the scattering due to the acoustical mode of lattice vibrations becomes of considerable importance in high‐purity crystals in an intermediate temperature range (between 34 °K and 12 °K) even for slow electrons.
Influence of Radiation Damage upon the Diffusion of Argon in Potassium Chloride
Authors: Schmeling P. 
Published: July 2007

AbstractThe diffusion of Ar41 and Ar39 in single crystals of potassium chloride is studied as a function of irradiation dose. It is found that the diffusion coefficients of argon are significantly decreased by increasing the irradiation dose. The influence of neutron bombardment is considerable at low temperatures, the diffusion coefficient being changed by several orders of magnitude. The general behaviour, as shown in an Arrhenius diagram, follows the same pattern independently of the irradiation dose. At high temperatures the diffusion coefficient is constant with time and has an activation energy of 8.7 ± 0.8 kcal/mol and an interstitial diffusion mechanism seems to be plausible. At intermediate temperatures the diffusion coefficient increases during isothermal annealing and ultimately reaches a constant value. At low temperature the diffusion coefficient is again constant with time.
Piezowiderstand von n‐Silizium in Abhängigkeit von der elektrischen Feldstärke
Authors: Asche M. , Bondar W. M. , Sarbej O. G. 
Published: July 2007

AbstractZur Untersuchung der Elektronentemperatur bei starken elektrischen Feldern in n‐Si wurde die Abhängigkeit des Piezowiderstandes von der elektrischen Feldstärke gemessen. Die experimentellen Resultate zeigen, daß diese Abhängigkeit nicht monoton ist, wie auf Grund der bestehenden Theorie erwartet wurde. Durch Näherungslösung der Boltzmanngleichung in Abhängigkeit von der elektrischen Feldstärke bei Anwesenheit von mechanischer Spannung wird eine Analyse der Bedingungen durchgeführt, bei denen eine solche nichtmonotone Abhängigkeit auftritt und die als Ursache dieser Erscheinung wirken. Die Ergebnisse der Berechnungen und der experimentellen Daten werden verglichen.
Relaxation Modes for Photon‐Induced Reorientation of M‐Centers in Alkali Halides
Authors: Turner T. J. , De Batist R. , Haven Y. 
Published: July 2007

AbstractDichroism is induced in potassium chloride crystals containing M‐centers by irradiation at low temperatures with polarized light in the F‐band. This dichroism arises from a reorientation of the M‐centers by ionic motion. The population of the six possible orientations of the M‐center can be described by six relaxation modes, depending on the direction of polarization of the light. Using group theoretical considerations, the relaxation modes are derived for the cases where the polarization of the light is in the [001] and [011] directions.
On the Kinetics of the Luminescence in KCl: Tl, KBr: Tl, and KI: Tl
Authors: Trinkler M. F. , Playavin I. K. 
Published: July 2007

AbstractThere are two theories on the kinetics of luminescence in KCl: Tl, KBr: Tl and KI: Tl, which are given in the papers [4 to 6] and [7 to 9]. In the present paper these theories are compared with known experimental results and this is found to lend support to the works [7 to 9].
X‐Ray and Optical Metallography of a Vapor Condensed Zinc Crystal Platelet
Authors: Armstrong R. W. 
Published: July 2007

AbstractThe Berg‐Barrett X‐ray diffraction contrast technique has been applied to searching for dislocations within a vapor condensed zinc crystal platelet and, also, to studying the crystal surface topography. Correlation of the X‐ray results with results from optical metallography and interferometry showed: (1) a few dislocations were present, at least, in several local regions of the crystal; and, (2) very shallow surface steps (≈2 × 10−5 cm) produced observable contrast in the X‐ray micrographs.
The Contribution of Multiple Vacancies to Self‐Diffusion
Authors: Seeger A. , Schottky G. , Schumacher D. 
Published: July 2007

AbstractThe deviations from a straight line of an Arrhenius plot of self‐diffusion coefficients are discussed in terms of the contribution of multiple vacancies to self‐diffusion. It is shown that for nickel the major part of the curvature may be accounted for by di‐ and trivacancy contributions. A small residual curvature of the Arrhenius plot is possibly indicative of a temperature dependence of the activation entropies.