bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ionenleitfähigkeit von reinen und dotierten AgBr‐ und AgCl‐Einkristallen
Authors: Müller P. 
Published: July 2007

AbstractEs wird über Leitfähigkeitsmessungen an AgBr‐ und AgCl‐Einkristallen im Bereich von −140 bis +400 °C berichtet. Aus den Meßergebnissen folgen neue Werte für die Fehlordnungskonzentration, die Fehlstellenbeweglichkeiten sowie für die Assoziation zwischen Fremdionen und Fehlstellen. Die Bildungsenergie von Frenkelpaaren beträgt im AgBr 1,06 eV und im AgCl 1,25 eV. Oberhalb 175 bzw. 250 °C muß eine zusätzliche Zunahme der Fehlordnungskonzentration infolge von Wechselwirkungseffekten berücksichtigt werden. Bei sorgfältiger Kristallpräparation ist der Einfluß der Grundverunreinigungen auf die Leitfähigkeit gegenüber strukturellen Störungen dominierend. Messungen unter Halogen‐Atmosphäre ermöglichten Aussagen über den Einbau dreiwertiger Fremdkationen sowie die Bestimmung der Konzentration der freien Defektelektronen.
Theory of CdS‐Type Superlinear Photoconductivity Due to Excitation from Localized Levels
Authors: Cardon F. 
Published: July 2007

AbstractThe free‐electron versus light‐intensity relationship in the superlinear range is calculated for a system consisting of two levels below the Fermi level and either one level or a continuous distribution, above it. The excitation of electrons from localized levels to the conduction band is also considered. It is shown that with respect to the inter‐band case two new possible values for lower break points are obtained, and that, in order to get superlinearity, excitations have to take place from the centres with smallest capture cross‐section for electrons. Values for upper break points due to thermal and optical quenching are unchanged. It is also shown that, in some cases, superlinearity exists for “localized level to conduction band” excitations and not for inter‐band excitations.
Übergangsstrahlung von dünnen Silberschichten
Authors: Bürker U. , Steinmann W. 
Published: July 2007

AbstractDünne Ag‐Schichten (200 bis 2000 Å) wurden mit mittelschnellen Elektronen (15, 25, 35 keV) bestrahlt. Die dabei auftretende Strahlung wurde hinsichtlich des Polarisationsgrades, ihres Spektrums im Bereich der Plasmawellenänge (3330 Å) und der Abhängigkeit ihrer Intensität von der Schichtdicke und der Elektronenenergie untersucht. Die Strahlung bestand vor allem aus Übergangsstrahlung, daneben auch aus Bremsstrahlung. Nach Abtrennung der letzteren stimmen die Meßergebnisse mit der berechneten Übergangsstrahlung überein. Sie werden im Modell der Plasmastrahlung diskutiert.
Photochemical Reactions at Low Temperatures in CdS Single Crystals
Authors: Korsunskaya N. E. , Markevich I. V. , Sheinkaman M. K. 
Published: July 2007

AbstractThe investigation of glow curves for various conditions of illumination in CdS single crystals (previously annealed at high temperatures) shows that in the temperature range +20 to −100°C new trapping centers arise photochemically. In the same temperature range new “sensitizing” recombination centres, having small capture cross‐sections for electrons, also arise due to a photochemical reaction. This causes the photoconductivity to be increased by a factor of 2 to 100. The investigation of the kinetics of trapping and recombination processes by various methods enables several parameters to be determined for the new trapping and recombination centers.
Electron Spin Resonance of Sulfur and Selenium Radicals in Alkali Halides
Authors: Schneider J. , Dischler B. , Räuber A. 
Published: July 2007

AbstractThree classes of paramagnetic radical molecules are detected in alkali halides by electron spin resonance: S3− and Se3−, SO2−, and SeO2−, and radicals formed by four equivalent sulphur or selenium atoms. The S3− and Se3− radicals occupy a trivacancy site formed by one metal and two halide vancancies. The C2‐axis of the radical is orientated along a face diagonal axis of the crystal. A hyperfine interaction of the unpaired electron with three S33 or Se77 nuclei is observed. The unpaired electron is localized in a II‐type molecular orbital formed by atomic p‐orbitals normal to the plane of the molecule. The S3− and Se3− centers are stable at room temperature. The electronic structure of the SO2− and SeO2− radicals is found to be analogous to that of S3− and Se3−. However, these radicals probably occupy only one halide vacancy site. Internal rotation is observed for SO2− and SeO2−, resulting in isotropic ESR‐spectra at elevated temperatures. Radicals formed by four equivalent sulphur or selenium atoms are detected in X‐irradiated chalcogen‐doped alkali halide crystals.
ENDOR Investigation of the S3− Sulphur Centre in KCl and NaCl
Authors: Suwalski J. , Seidel H. 
Published: July 2007

AbstractA paramagnetic sulphur centre with orthorhombic 〈110〉 symmetry, described by Schneider et al. [1], is studied by ENDOR in KCl and NaCl crystals. Hyperfine and quadrupole interactions with alkali and halogen neighbours can be resolved. The principal axes of all the observed interactions are near the [001] centre axis. This fact and the observed symmetries strongly support the model of a bent S3− molecule‐ion occupying a corresponding KCl2− or NaCl2− trivacancy in the (001) plane. The ESR linewidth and hyperfine structure due to central S33 nuclei (KCl: S33 11.56% enriched) support this model.
The Contribution of Domain‐Wall Oscillations to the Small‐Signal Permittivity of Triglycine Sulphate
Authors: Fousek J. , Janoušek V. 
Published: July 2007

AbstractThe complex permittivity ϵ* of ferroelectric triglycine sulphate is measured in a weak ac field in the frequency range 5 × 102 to 5 × 107 Hz as a function of the net polarization Pa of the sample. The value of Pa is adjusted in steps by charge supplied from a parallel capacitor. Throughout the frequency range both components of ϵ* are larger for crystals with |Pa|≠|Ps| than for a single‐domain crystal with |Pa| = |Ps|. This indicates a contribution Δϵw* to the permittivity by the domain walls. The imaginary component Δϵw″ is an order of magnitude greater than the value of ϵ″ of a singel‐domain crystal; Δϵw′ is up to five times larger than the ϵ′ of a single‐domain crystal. The frequency dependence of Δw* suggests contributions from two different mechanisms. The frequency dependence of one of them is given approximately by the Debye equations with τ ≈ 10−7 s. Both components of the second contribution to Δϵw* decrease monotonically with frequency. The probable mechanisms of these contributions are discussed.
Theory of CdS‐Type Superlinear Photoconductivity Due to Simultaneous Excitation from Localized Levels and the Valence Band
Authors: Cardon F. 
Published: July 2007

AbstractConditions and values of breakpoints for superlinear photoconductivity, due to the simultaneous excitation of electrons into the conduction band from localized levels and the valence band, are derived for a simplified system consisting of three levels in the band‐gap. The photon energy dependence of this case of superlinearity is also discussed.
Strength and Structure of Thin Vacuum‐Evaporated Metallic Films
Authors: Ya. Pines B. , Chanh Nguyen Xuan 
Published: July 2007

AbstractThe structure and substructure of thin films of Al, Ag, Ge, and Ni with thicknesses in the range 100 to 700 Å, are investigated using an electron microscope and electron diffraction techniques. The results are compared with a previous determination of the thickness‐dependence of the strength of the films [1]. The structure and substructure of Au, Ag, and Ge films of uniform thickness (about 200 to 300 Å) are changed by various heat treatments following the measurement of their strength. The origin of the higher strength of the films is discussed on the basis of the results obtained.
Spin Wave Dispersion in Thin Cobalt Films
Authors: Wojtczak L. 
Published: July 2007

AbstractA dispersion law for the energy spectrum of thin films of hexagonal cobalt is obtained on the basis of the Heisenberg Hamiltonian and the Holstein‐Primakoff approximation. The general formulation is discussed for an arbitrary system of ferromagnetic thin films. The calculations include an effective anisotropy field.
Evaluation of Specific Heats of Titanium, Zirconium, and Hafnium
Authors: Gupta R. P. , Dayal B. 
Published: July 2007

AbstractThe electron gas model, described by the authors in an earlier paper, is extended to the three transition metals titanium, zirconium, and hafnium. The theoretic θ − T curves agree to within 3 to 5% with experimental values.
Vibrational Spectrum and Specific Heat of Potassium on Sharma and Joshi's Electron Gas Model
Authors: Gupta R. P. , Kishore B. 
Published: July 2007

AbstractThe vibrational spectrum and specific heat of potassium are calculated by using Sharma and Joshi's electron gas model for monovalent metals. The calculations are based on Houston's approximation for the frequency spectrum. The calculated lattice specific‐heat and the corresponding equivalent Debye temperature are compared with experimental data and the results are discussed.
Photoleitungs‐ und Lebensdauermesungen an Tellur
Authors: Grosse P. , Winzer K. 
Published: July 2007

AbstractAn undotierten Tellur‐Einkristallen wurden Photoleitungs‐ und Lebensdauermessungen bei 20 bis 90 °K ausgeführt. Der für die Polarisationsrichtungen E ⟂ c und E | c auf {1010}‐Flächen bzw. E ⟂ c auf {0001}‐Flächen bestimmte spektrale Verlauf der Photoleitung wird diskutiert und zur Berechnung der Oberflächen‐Rekombinationsgeschwindigkeit verwendet. Polarisationsabhängige Oszillationen in den Photoleitungsspektren polierter Spaltflächen werden als Interferenzen in einer durch die Politur strukturgestörten Oberflächenschicht gedeutet.
Lebensdauer und Driftbeweglichkeit von Defektelektronen in AgBr‐Kristallen bei Zimmertemperatur
Authors: Heukeroth U. , Süptitz P. 
Published: July 2007

AbstractDie Untersuchungen erfolgten mit Impulsmethoden an keilförmigen Kristallen. Photodefektelektronen werden durch ein äußeres elektrisches Feld durch den Kristall hindurchgetrieben und durch ihre Wirkung auf Silberatome, die sich auf der Oberfläche befinden, nachgewiesen. Es wird festgestellt, daß zwischen der Defektelektronenlebensdauer im Volumen und der in einer oberflächennahen Schicht unterschieden werden muß. Für die untersuchten Kristalle beträgt die Lebensdauer im Volumen im Mittel 0,4 μs und an der Oberfläche oder in ihrer Nähe 80 μs. Die Lebensdauer im Volumen erweist sich als stark abhängig von der Kristallvorgeschichte und‐reinheit. Die Driftbeweglichkeit der Defektelektronen bei Zimmertemperatur beträgt 1,1 cm2/Vs.
Thermal Conductivity of Selenium
Authors: Abdullaev G. B. , Mekhtieva S. I. , Sh. Abdinov D. , Aliev G. M. , Alieva S. G. 
Published: July 2007

AbstractThe thermal conductivity λ of amorphous, crystalline, and liquid selenium (purity 99,99999 %) is measured in the temperature range 80 to 525°K which includes the softening (T ≈ 31°C) and melting points. The thermal conductivity of amorphous selenium increases linearly with temperature up to 304°K at which temperature there is a discontinuity involving a sharp increase of about 40%. Admixtures of Cd and Tl change the values of the discontinuity Δλg and temperature Tg. An admixture of Cd shifts the value of Δλg from 0.44 × 10−3 to 0.11 × 10−3 cal/(cm s degree) and increases Tg from 30.7 to 33.5°C. Heat treatment increases λ and changes its temperature profile. Admixtures of Tl remove the discontinuity. The thermal conductivity of selenium during melting undergoes a discontinuity of about 40% which is explained by the increase in the intermolecular distance from 3.46 to 3.74 Å. A photon thermal conductivity, which accounts for up to 30% of the overall thermal conductivity, is found in crystalline selenium at temperatures above about 350°K. The experimentally determined value of λ, its temperature dependence, the values of the softening and melting discontinuities and the photon parts agree well with theory.
Growth and Structure of Evaporated Silicon Layers
Authors: Thomas D. J. D. 
Published: July 2007

AbstractSilicon, on heating in a vacuum at pressures of less than 10−6 Torr, reacts with residual organic vapours to form silicon carbide which may grow epitaxially. Growth of evaporated silicon layers commences in etch pits produced during the annealing pretreatment. Deposition continues until the etch pits become filled, when the layer becomes continuous by lateral spreading from the initial islands. Most of the defects observed are due to stacking disorders formed in the initial growth islands. Many of these defects are removed by interaction with one another as the layers become thicker.
Structure of Boron‐Nitride Fibers
Authors: van Torne L. I. 
Published: July 2007

AbstractA transmission electron microscopy and electron diffraction investigation of BN fibers 5 to 7 μm in diameter indicates that the structure can be interpreted in terms of atomic disorder over distances comparable to the atomic spacing. Thermal conductivity considerations suggest that the disorder results from the “quenching in” of thermally induced atomic vibrations.
Extension of the Howie‐Whelan Equations for Electron Diffraction to Non‐Centro Symmetrical Crystals
Authors: Gevers R. , Blank H. , Amelinckx S. 
Published: July 2007

AbstractThe Howie‐Whelan system of equations [2] is extended to non‐centro symmetrical crystals. This system of equations, which is valid for the Laue case, describes the scattering of electrons by a perfect crystal in the two‐beam approximation and takes anomalous absorption into account. The theory predicts that Friedel's law no longer holds for the dark field image but is still valid in the bright field. Observations on 180° walls in barium titanate support the theory. In addition the theory shows that 180° walls in inclined planes should produce α‐type fringes. This phenomenon is also observed experimentally.
Ordering of Interstitial Impurities in Niobium
Authors: van Landuyt J. , Gevers R. , Amelinckx S. 
Published: July 2007

AbstractThe ordering phenomenon in niobium is studied by electron microscopy and by electron diffraction. The phenomenon is found in parts of niobium foils subjected to an annealing treatment in vacuum. Domains are formed which, on the basis of the present model, are due to the ordering of interstitial oxygen atoms. The insertion of the interstitials on a superlattice in the nobium matrix causes a deformation of the latter in a 〈110〉 direction. The domain structure results from the fact that several orientations are possible for the superlattice. Further evidence for this ordering is deduced from the presence of superlattice dislocations and of supplementary spots in the diffraction patterns. The superlattice is deduced from the diffraction data and a composition Nb2O is attributed to this metallic oxide phase. The domains are revealed by fringe contrast at the boundaries and by the change in background intensity. Both contrast effects are associated with the slight deformation due to the ordering. A discussion is included of a second type of fringe pattern which is often observed in annealed niobium. Patterns of this type have previously been attributed to the presence of stacking faults; it is shown here that they are due to plate‐shaped precipitates of some oxide phase in the niobium matrix.
Remarks on the Recombination of Electrons and Donors in n‐Type Germanium
Authors: Beleznay F. , Pataki G. 
Published: July 2007

AbstractThe cascade theory of the recombination of electrons into ionized donors is critically examined in this paper. It is shown that in Lax's model, and also in the work of Hamann and McWhorter, the neglect of lower lying states leads to an overestimate of overestimate of the sticking probability. It is also shown, that the model proposed by Ascarelli and Rodriguez ‐ which neglects the higher excited states ‐ does not lead to the experimental value for the total capture cross‐section.
Umverteilung heißer Elektronen auf die Täler des Leitungsbandes von Silizium
Authors: Asche M. , Bondar W. M. 
Published: July 2007

AbstractEs wird eine Möglichkeit zur Abschätzung der Elektronenumverteilung auf die Täler in Vieltalhalbleitern bei elektrischen Feldern gezeigt. Sie ist auf der Änderung der Besetzungszahlen der Täler bei Druck begründet. Experimente wurden an 20 Ωcm n‐Si bei 77°K durchgeführt und entsprechend ausgewertet. Die Resultate stimmen qualitativ mit den Daten aus Anisotropiemessungen der Leitfähigkeit überein.
Untersuchungen an halbleitenden Indiumoxydschichten
Authors: Groth R. 
Published: July 2007

AbstractNach dem „Sprühverfahren”︁ wurden n‐leitende Indiumoxydschichten mit Schichtdicken zwischen 0,1, und 0,5 μm auf Glasplatten hergestellt und die Herstellungsbedingungen dieser Schichten untersucht. Die Leitfähigkeit der Schichten liegt je nach Dotierung zwischen 1,5 × 102 und 4,3 × 103 Ω−1cm−1 und die Konzentration and freien Ladungsträgern zwischen 1019 und 6 × 1020 cm−3. Die Beweglichkeit der freien Ladungsträger hängt erheblich von der jeweiligen Dotierung ab und wird vermutlich durch Streuung an den Korngrenzen der mikrokristallinen Schicht bestimmt. Die Schichten sind im sichtbaren Spektralbereich absorptionsfrei und zeigen im Ultrarot wegen der hohen Konzentration freier Ladungsträger ein hohes Reflexionsvermögen.
L'approche à la saturation de l'aimantation des corps ferromagnétiques polycristallins de structure cubique
Authors: Vergne R. 
Published: July 2007

AbstractL'auteur établit l'expression de la loi d'approche à la saturation de l'aimantation des corps ferromagnétique polycristallins de structure cubique sous la forme d'un développement en série qu'il pousse jusqu'au terme en H−3. Il introduit l'interaction magnétique des cristallites et tient compte de K2 dans l'expression de l'énergie magnétocristalline. Il compare ensuite quantitativement la théorie et l'expérience dans le cas du fer et du nickel.
The Influence of External Electric Fields on the Absorption of Ag+ ‐Centres in KCl (I)
Authors: Gebhardt W. , Mohler E. 
Published: July 2007

AbstractA method of measuring the transverse Stark effect of point defect absorption in ionic crystals at low temperatures is described. The absorption bands of KCl: Ag+ in the UV region show an increase in the oscillator strength of about Δf/f ≈ 8 × 10−4 and a shift, predominantly to the low energy side, of about Δε ≈ 8 × 10−6 eV under external fields of 105 V/cm.
The Temperature Dependence of the F‐Centre Absorption and Emission in Five Alkali Halides
Authors: Gebhardt W. , Kühnert H. 
Published: July 2007

AbstractThe temperature dependence of the F‐centre absorption and emission bands in NaCl, KCl, RbCl, KBr, and KI is measured. The peak energies and half widths at T = 0°K, the effective phonon frequencies, and the parameters of the maximum shift are determined.
Trapping of Holes in Silver Bromide Single Crystals
Authors: Platikanowa W. , Malinowski J. 
Published: July 2007

AbstractThe reaction between a deposit of silver and neutral bromine formed by holes migrating to the surface of a silver bromide crystal is used to investigate the concentration decay of holes in the interior of the crystal. The effective lifetime of photoexcited holes in a thin surface layer is shown to be at least an order of magnitude larger than the bulk lifetime. Thermal annealing of the samples substantially increases the bulk trapping rate whilst leaving the surface rate unchanged. The observations are explained in terms of a layer of adsorbed bromine formed at the surface of the crystal during exposure. It is shown that an effective bromine acceptor is necessary for the formation of a stable surface latent image. No relation is found between the lifetimes of photoexcitedle ectrons and holes, which suggests that these carriers do not recombine with one another. The nature and concentration of the trapping centres and the effect of annealing the crystals is discussed.
Radiation Annealing in Cuprous Oxide
Authors: Vajda P. 
Published: July 2007

AbstractExperimental results from high‐intensity γ‐irradiation of cuprous oxide are used to investigate the annealing of defects with increasing radiation dose. The results are analysed on the basis of the Balarin and Hauser [3] statistical model of radiation annealing, giving a square‐root relationship between the rate of change of resistivity and the resistivity change. The saturation defect density at room temperature is estimated on the basis of a model for defect creation in cuprous oxide.
NMR Evidence for Contact Hyperfine Coupling in Paramagnetic UF4
Authors: Pintar M. 
Published: July 2007

AbstractThe F19 NMR absorption in powdered UF4 is investigated in the temperature range 122 to 433 °K at magnetic fields between 10000 and 5000 G. The fluorine absorption pattern in this paramagnetic material with seven nonequivalent F‐sites in the unit cell is reproduced qualitatively by a sum of six asymmetric component lines (H∥ ‐– H⊥)−1/2 × (H–H⊥)−1/2, some of which are shifted in the high field direction, and some in the low field direction. The occurrence of low‐field shifted components provides evidence of contact hyperfine interaction between the magnetic electrons and the fluorine nuclei whereas the occurrence of high‐field shifted components may arise from indirect coupling through electron transfer, and indicates partial covalent bonding between the magnetic electrons and the surrounding fluorine ions. This is supported by magnetic susceptibility and EPR data.
Effect of Hydrostatic Pressure on the Elastic Behavior of Cubic Crystals
Authors: Ghate P. B. 
Published: July 2007

AbstractFinite deformation theory is used to calculate the effective second order elastic constants (cik′) of a cubic crystal subjected to very high pressures. We obtain cik′ = cik + A η + B, where A and B depend on the second order and higher order elastic constants and η depends on the pressure.
Paramagnetic Resonance of Pt3+ Ions in BaTiO3 Single Crystals
Authors: Šimánek E. , Šroubek Z. , Žďánský K. , Kaczér J. , Novák L. 
Published: July 2007

AbstractThe paramagnetic resonance of Pt3+ ions in niobium doped BaTiO3 single crystals is investigated at a temperature of 4 °K. The hyperfine parameter A is found to be (0 ± 5) × 10−4 cm−1. The hyperfine field resulting from core polarization by the unpaired 5d‐electrons in platinum is deduced using this value.
Experimental Investigation of Some Features of Incoherent Rotation in Thin Permalloy Films
Authors: Telesnin R. V. , Ilicheva E. N. , Kolotov O. S. , Nikitina T. N. , Pogozhev V. A. 
Published: July 2007

AbstractSome features of the mechanism of inhomogeneous rotation in thin permalloy films, reversed by pulse fields are investigated: switching coefficient, threshold fields, parameters of transitions to fast magnetic reversal. The behaviour of the films are also investigated for fields applied along the “hard” axis. The results are compared with static parameters of thin films: anisotropy field, angular dispersion and domain structure.
Der vektorielle Photoeffekt an Kalium
Authors: Brauer M. 
Published: July 2007

AbstractAn im Hochvakuum aufgedampften dicken, polykristallinen Kaliumschichten wird mit linear polarisiertem Licht im Energiebereich zwischen 2,25 und 5,20 eV die Winkelabhängigkeit der Ausbeute des äußeren Photoeffektes gemessen. Für alle Einfallswinkel Θi und für beide Orientierungen des elektrischen Vektors E ergibt sich dabei stets ein Maximum für einfallendes Licht der Energie ℏω = 3,1 eV. Der selektive Effekt Yp(ℏω, Θi) (E parallel zur Einfallsebene) ist immer größer als der normale Effekt Ys (ℏω, Θi) (E senkrecht zur Einfallsebene) und durchläuft für jede Frequenz in Abhängigkeit vom Lichteinfallswinkel einen Maximalwert, während der normale Effekt für Frequenzen in der Nähe der langwelligen Grenze mit steigendem Einfallswinkel monoton fällt; für größere Werte von ℏω weist jedoch auch der normale Effekt ein Maximum auf. Durch Bildung des Quotienten Yp/Ys erhält man den sogenannten Vektoreffekt der Ausbeute, der sowohl in Abhängigkeit von der Frequenz als auch vom Einfallswinkel einen Maximalwert durchläuft. Die experimentellen Ergebnisse werden abschließen diskutiert.