bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal and infrared quenching of photoconductivity in n‐InSe single crystals
Authors: Abdullaev G. B. , Kh. Alieva M. , Mamedova A. Z. 
Published: July 2007

AbstractThermal and infrared quenching of photoconductivity is studied in sensitive n‐InSe single crystals. It is found that thermal quenching occurs from 143 to 223 °K and that infrared quenching takes place below 165°K. Infrared quenching bands are found at 0.75 eV and 0.9 eV. The thermal quenching indicates a level which is 0.2 eV from the upper limit of the v‐zone and gives the electron and hole capture cross‐section ratio Sp/Sn as 2 × 102 for the sensitizing centres and their concentration ratio N2/N1 as 2. On the basis of the thermally stimulated current the binding energy of the attachment level is 0.16 eV.
On the four‐axis hexagonal reciprocal lattice and its use in the indexing of transmission electron diffraction patterns
Authors: Okamoto P. R. , Thomas G. 
Published: July 2007

AbstractA four‐axis hexagonal reference basis can be constructed in the reciprocal space of hexagonal crystals in such a way that the resulting lattice contains as a subset all the points of the conventional reciprocal lattice. All other points not belonging to this subset have no physical significance since they have non‐integral indices and hence cannot represent real crystal planes. Since these points cannot register as spots in an actual diffraction pattern, the four‐axis hexagonal lattice and the conventional reciprocal lattice are physically indistinguishable. _ The interpretation of diffraction patterns of hexagonal crystals is easier when indexing is referred to the four‐axis basis. The necessary crystallographic relationships can be obtained directly in terms of Miller‐Bravais indices using elementary vector analysis and when applied to Kikuchi electron diffraction maps, the problem of determining the foil orientation becomes especially simple.
Thermo‐ und Elektrotransport in β‐titan und β‐zirkonium
Authors: Dübler H. , Wever H. 
Published: July 2007

AbstractIn β‐Titan und β‐Zirkonium mit einem Reinheitsgrad von nahezu 99,9% erfolgt der Thermotransport zum heißen Probenende, der Elektrotransport zur Anode. Das Verhältnis von Transportwärme Q* (in kcal) und effektiver Ladung z* beträgt für β‐Ti 43, für β‐Zr55. Die Aktivierungsenergie des Thermotransports hat für β‐Ti einen Wert von etwa 27 kcal, für β‐Zr von 16 kcal. Sie weicht damit für β‐Zr deutlich von dem für die Selbstdiffusion bekannten Wert ab. Die Messungen schließen die Möglichkeit aus, das anomale Diffusionsverhalten der untersuchten Metalle durch einen Zenerschen Ringmechanismus zu erklären. Eine widerspruchsfreie Deutung aller Versuchsergebnisse ist dagegen durch die Annahme eines Versetzungsmechanismus möglich, bei dem der Bereich um den Versetzungskern, in dem die Diffusion beschleunigt ist, für β‐Ti größer als für β‐Zr ist.
Deformation of molybdenum single crystals at slow rates of strain
Authors: Guiu F. 
Published: July 2007

AbstractMolybdenum single crystals were deformed in tension, and the relationship between stress, strain, and strain rate was studied in the pre‐yield region. The high work‐hardening rate of the pre‐yield deformation is explained in terms of the exhaustion of mobile edge dislocation segments. The rate of exhaustion, ∂ log ϱ/∂ϵ, is of the order of 103 to 104. The temperature and strain rate dependence of the stress required to deform the crystals at strain rates < 10−7 s−1 was investigated at strains > 0.01. The activation energy and activation volume have values between 2 and 4 eV, and between 50 and 100 b3 respectively. This result suggests that the mechanism of overcoming the Peierls friction is not rate controlling at the slow rates of strain. Alternative interpretations are discussed.
Optical absorption of the impurity ag and models for the E‐Band in an alkali halide
Authors: Arora H. L. , Kim S. , Wang S. 
Published: July 2007

AbstractA method used in more recent work is applied to the calculation of optical absorption of a neutral silver atom (AgI) in KCl. The predicted results show that the E‐band in KCl: Ag is not due to the impurity AgI located at a substitutional site of the host crystal. From present theoretical results we then propose two speculative models for the origin of the E‐band: 1. The E‐band is due to the impurity AgI located at an interstitial site tetrahedrally surrounded by four alkali ions as well as by four halide ions. 2. The E‐band is due to the interstitial impurity AgI perturbed by some complex whose perturbation is very small.
Electron microscope observations of twinning and phase transformations in indium sulfide crystals
Authors: Fitzgerald A. G. , Thomas G. 
Published: July 2007

AbstractThin crystals of indium sulfide with the crystal structures corresponding to the compositions InS and In6S7 have been grown by means of a chemical transport reaction. Phase transitions have been induced by beam heating in the electron microscope and have been identified by electron diffraction. Crystals of InS occasionally contain twins when examined in the electron microscope. The twins presumably originate during the growth process. On subjecting these crystals to high intensity electron irradiation in the electron microscope large numbers of twins are nucleated. On continued electron irradiation structural transformations occur in these crystals. Crystals with the orthorhombic InS structure transform to the monoclinic In6S7 structure and on further electron irradiation a further transformation to the tetragonal In2S3 structure occurs. When crystals with the monoclinic In6S7 structure are subjected to high electron beam intensities in the electron microscope, a structural transformation also occurs and the crystals transform to the tetragonal In2S3 structure.
Computer calculations for vacancies in alkali halides with NaCl structure
Authors: Scholz A. H. 
Published: July 2007

AbstractIn calculations of the energies of point defects in ionic crystals one conventionally divides the crystal into two regions. Region I contains the defect and a number of its neighbours and all relaxations in region I are handled explicitly. Region II is the rest of the crystal and assumed analytical solutions are used here. All previous calculations have used a rather small region I. A computer method presented in a previous article [12] has been significantly improved and permits the treatment of a large region I containing 256 ions around the vacancy. In particular the polarization energy UPol was handled much more accurately than before, the electric fields EP and EDip in region I due to monopoles and dipoles of the ions being the relevant quantities. Since the lattice around the vacancy has full cubic point symmetry we expand EP and EDip in power series of the displacements σ and dipoles m, and the associated coefficients of such series were evaluated numerically. The Coulomb energy UCoul was treated in a similar way. Hence we obtained suitable and very fast computer programmes for the lattice energy of region I. The evaluated 4733 constant coefficients are included in these programmes. Following Boswarva and Lidiard the effect of region II had to be taken into account; also the interaction of ions in region I with those in region II was estimated. Several numerical results for the vacancy calculations are described.
Piezoelectricity in iii‐v compounds with a phenomenological analysis of the piezoelectric effect
Authors: Arlt G. , Quadflieg P. 
Published: July 2007

AbstractThe piezoelectric stress constants e14 of InSb, InAs, GaSb, GaAs, and AlSb have been measured at room temperature and found to be 0.071; 0.045; 0.13; 0.16, and 0.068 C/m2 respectively. If the III‐V compound crystals are expanded in the <III> direction, the A‐faces (metal atoms) become negatively charged, in contrast to II‐VI compounds, in which the equivalent faces become positively charged. Using a model of a layered lattice, we show that three different mechanisms may contribute to the piezoelectric effect. These mechanisms are 1. the internal displacement of the ionic charge, 2. the internal displacement of the electronic charge. 3. the change in ionicity due to strain.
On the mathematical description of electrical processes in semiconductors. i. phase space analysis in subspaces of dimension lower than three
Authors: Oberländer S. , Sikorski S. 
Published: July 2007

AbstractA theoretical study is made of the transport of non‐equilibrium carriers in semiconductors in the stationary case which includes arbitrary deviations from thermodynamic equilibrium. Classes of systems of solutions with various qualitative properties are given without approximation for the system of differential equations. The equations are the continuity equations with a recombination law based upon the law of mass action, and the common current equations and Poisson's equation. The systems of solutions are applicable to various problems in homogeneous semiconductors and inhomogeneous semiconductor devices. They offer possibilities of testing numerical methods and obtaining new approximate methods. Finally they lead to some remarks on the neutrality approximation.
Vacancies, divacancies, and self‐diffusion in platinum
Authors: Schumacher D. , Seeger A. , Härlin O. 
Published: July 2007

AbstractThin wires of high‐purity platinum are quenched from high temperatures by means of the helium‐II technique. After quenching from about 1000 °C the electrical resistivity is found to recover between 380 and 520 °C with an activation energy of (1.33±0.05) eV. After quenching from near the melting point the recovery occures between 200 and 460°C and can be decomposed into two second‐order processes with activation energies of 1.0 and 1.34 eV, respectively. The self‐diffusion data are re‐analysed allowing for the contribution of both mono‐ and divacancies. This analysis is compared critically with the results of the present quenching experiments and with previous work. A consistent set of vacany parameters is proposed for Pt.
Untersuchung der Fermifläche des Molybdän durch Zyklotronresonanzmessungen
Authors: Herrmann R. 
Published: July 2007

AbstractZyklotronresonanzmessungen im Mikrowellenbereich bei einer Frequenz von 9,7 GHz gestatteten die effektiven Massen von Molybdän und ihr Anisotropieverhalten in den kristallographischen Ebenen (110) und (121) bei einer Temperatur der Meßproben von 1,6 °K zu bestimmen. Bei beliebiger Orientierung des Magnetfeldes wurden in beiden Ebenen stets mehrere Zyklotronresonanzserien beobachtet, was auf die Kompliziertheit der Fermifläche des Molybdän hinweist. Ein Teil der beobachteten effektiven Massen konnte dem Modell der Fermifläche zugeordnet werden. Es wurde die Geschwindigkeit der Elektronen auf dem zentralen Teil der Hauptelektronenfläche, dem Elektronenjack, zu vc = 0,56 ×× 108 cm/s abgeschätzt.
X‐Ray production and thermal annealing of frenkel pairs in KCl
Authors: Giuliani G. , Reguzzoni E. 
Published: July 2007

AbstractThe X‐ray production and thermal annealing α‐centres (isolated negative ion vacancies) are studied in KCl as a function of purity and the temperature of irradiation. At any temperature the α‐centre production results from competition between the formation process and thermally activated destruction of negative ion vacancies. Since the latter process is strongly temperature and structure dependent, the α‐centre production is structure sensitive or insensitive depending on the temperature of irradiation. From the point of view of thermal stability the α‐centres produced by X‐rays can be divided into two groups. The first group includes α‐centres which decay below 77 °K and whose thermal stability does not depend on the purity of the sample. The second group includes α‐centres which decay in the 100 to 250 °K temperature range and whose thermal stability is strongly structure sensitive. Finally, some results on the influence of electron traps on α‐centre formation are reported.
On the specific heat of dilute magnetic alloys
Authors: Sólyom J. , Zawadowski A. 
Published: July 2007

AbstractIt is shown that for the Kondo model of dilute magnetic alloys a mass renormalization due to an energy dependent self‐energy causes no enhancement of the specific heat. It is proved that in the homogeneously polarized state the mass renormalization is caused by ∑ (ω) ≈︁ ‐ α ω and therefore the observed excess specific heat in dilute magnetic alloys comes from the inhomogeneity of the polarization. In external magnetic fields a contribution to the specific heat appears, which, in high field, is inversely proportional to H.
Preparation and some properties of CuP2 single crystals
Authors: Goryunova N. A. , Orlov V. M. , Sokolova V. I. , Shpenkov G. P. , Tsvetkova E. V. 
Published: July 2007

AbstractCuP2 monocrystals of about 1 cm2 area are grown by crystallization from the solution in tin. The habit and the monocrystalline structure of the compound is investigated by chemical, X‐ray, and microstructure methods. Following semiconductor parameters are determined (at room temperature): Eg ≈︁ 1,4 eV, n = 7.5× 1017 to 8 × 1017 cm−3, α = + 800 μV/deg, and σ = 10 Ω−1 cm−1.
Lifetime of excited Cu+ in alkali halides
Authors: Baldini G. , Jean A. , Spinolo G. 
Published: July 2007

AbstractAn experimental study is made of the time decay of excited Cu+ ions diluted in potassium halides in order to determine the role of the host crystal in the impurity absorption and emission processes. The Cu+ ions are responsible for a few ultraviolet absorption bands which, after optical stimulation, give rise to emission at ≈︁ 4000 Å. The lifetime, τR, of the lowest excited state, presumably 3d94s, is measured and found to be ≈︁ 50 μs in KCl:Cu, ≈︁ 100 μs in KBr:Cu and ≈︁ 5 μs in KI:Cu). The thermal de‐excitation energies, ΔEd, are also measured and found to be ≈︁ 0,73 eV (KCl:Cu), ≈︁ 0,76 eV (KBr:Cu), ≈︁ 0,61 eV (KI:Cu). These results together with measurements of other workers may suggest that the transition 3d10 ≈︁ 3d94s, forbidden in the free ion, becomes partially allowed due to the crystal field. The implications of an off‐centre position of the Cu+ ion inthe K+ vacancy are also discussed and found to be consistent with the experimental data.
Investigation of grain boundary energetics in Er2O3 thin foils by transmission electron microscopy
Authors: Murr L. E. 
Published: July 2007

AbstractThe oxidation of erbium thin films directly within the electron microscope, and the subsequent grain growth and equilibration of the Er2O3 foils have allowed the true dihedral angles at grain boundary triple junctions to be calculated. It is observed that a mean dihedral angle of 120° obtains for these oxide‐ceramic films; and the comparison of the three‐dimensionally computed dihedral angles with the two‐dimensional angles measured directly from electron microscope images of grain boundary triple junctions in Er2O3 exhibited a uniqueness which questions the necessity of three‐dimensional corrections for this particular property. The distribution of relative grain boundary free energy ratios in Er2O3 foils is also calculated; and the spread of this data is interpreted to represent the effects of the relative grain orientations composing a triple junction. The mean boundary inclination is observed to be 71.1°, which suggests an influence on grain boundary equilibration in thin foils of surface image forces. The results generally indicate that the application of techniques previously utilized in the study of metallic grain boundary energetics is equally valid in certain oxide‐ceramic thin films.
Diffusion in Inert‐Gas bombarded KCl, KBr, and KI
Authors: Kelly R. , Jech Č. , Matzke H. J. 
Published: July 2007

AbstractA study of inert‐gas diffusion, mainly involving Kr and Xe, in ion‐bombarded KCl, KBr, and KI has been made using bombardment energies up to 85 keV and doses up to 50 μA min/cm2. Two types of release behavior were observed, both of which were shown to be compatible with diffusion kinetics, at least to first approximation. Low doses led to release with a fairly well‐defined ΔH of 33.5, 30.5, and 28.5 kcal/mol for KCl, KBr, and KI respectively, while high doses led to release with a somewhat variable ΔH having mean values of 44, 39, and 33.5 kcal/mol for KCl, KBr, and KI respectively. It is proposed that the low‐dose release involves gas motion without an implied gas—gas or gas—damage interaction, the gas perhaps occupying the small, stable vacancy clusters recently discussed by one of the authors (Hj. M.). The high‐dose release seems, by contrast, to be affected by transient gas—gas or gas—damage interactions, and is probably identical with the process found in homogeneous‐labelling work between about 250 °C and the “knee” temperature. A third type of release, found in homogeneous‐labelling work above the “knee”; temperature, has no parallel in ion‐bombardment work. It is here tentatively attributed to the motion of small, gas‐filled bubbles, and its ΔH of 7 to 14 kcal/mol is proposed to be related to that for surface diffusion of the host crystal.
Electron microscopic investigation of lamellar mixtures of two close‐packed phases
Authors: Delaey L. 
Published: July 2007

AbstractMartensitic and massive phases containing fine lamellae of two different close‐packed structures have been studied by transmission electron microscopy. The stacking sequences involved in the lamellar mixtures are ABCBCACAB and ABC, or AB and ABC, or ABC and CBA. The fine lamellae produce fringe patterns which are similar to fringe patterns due to single stacking faults. However, by tilting the foil images can be obtained that are incompatible with single stacking faults.
Approximate symmetry relations for double group k · p expansions
Authors: Broerman J. G. 
Published: July 2007

AbstractA recent calculation [9] of the energies of the Δ7 (“extra”) representations of the double group of the wave vector Δ in germanium is examined. This calculation employs a double group formalism in which matrix elements of the momentum connecting Γ7+ and Γ8+ with other states are independent. It is here shown that there exist symmetry relations between these matrix elements which are only weakly broken by interband spin‐orbit interaction, and that it is thus not physically meaningful to regard the elements as independent.
Neutron Diffraction Studies of α‐FeOOH
Authors: Szytuła A. , Burewicz A. , Dimitrijević Ž. , Kraśnicki S. , Rżany H. , Todorović J. , Wanic A. , Wolski W. 
Published: July 2007

AbstractNeutron spectrometric investigations are made of goethite (α‐FeOOH) of mineralogical and synthetic origin (α‐FeOOH of natural isotopic composition) and also of α‐FeOOD using a monochromatic neutron beam of λ = 1.12 Å. Some powder diffraction patterns in the temperature range from −190 to +120°C are measured. The obtained coordinates for all atoms (including those for hydrogen) in the unit cell are given. The existence of antiferromagnetic spin ordering at temperatures below +80°C is observed. A model is proposed in which the spins are aligned parallel to the b‐axis.
Thermal Capacity of Solid Nitrogen
Authors: Bagatskii M. I. , Kucheryavy V. A. , Manzhelii V. G. , Popov V. A. 
Published: July 2007

AbstractThe thermal capacity of solid nitrogen in the temperature range 2.6 to 15°K is investigated using an adiabatic calorimeter of original construction. The analysis of the results of this paper and the literature data on the thermal capacity allow information about the character of the rotational motion of the molecules in crystalline nitrogen to be obtained. The so‐called orientation defects give a considerable contribution to the thermal capacity near the temperature (35.6°K) of the phase transformation. In the high‐temperature β‐phase of solid nitrogen the practically free rotation of the molecule occurs.
X‐Ray Dynamical Contrast of a Planar Defect
Authors: Authier A. , Milne A. D. , Sauvage M. 
Published: July 2007

AbstractThe presence of a non‐diffracting lamella in an otherwise perfect crystal results in particular interference fringes on X‐ray topographs. The form and contrast of these fringes as found on section topographs have been calculated using the basic assumptions of the dynamical theory. Two different types of fringes can be distinguished: those independent of the gap thickness which are similar to stacking fault fringes, and those characteristic of a gap, whose shape depends sharply on the gap thickness. It is shown that among these interference systems some fringes of high contrast exist even in absorbing crystals. The experimental results obtained with various geometric arrangements are in good agreement with the theoretical predictions.
Slip Line Pattern and Active Slip Systems of Tungsten and Molybdenum Single Crystals Weakly Deformed in Tension at Room Temperature
Authors: Kaun L. , Luft A. , Richter J. , Schulze D. 
Published: July 2007

AbstractElectron zone‐refined tungsten and molybdenum single crystals are deformed in tension at room temperature. The slip systems on the cylinder‐shaped tensile specimens are determined using the light as well as the electron microscope. The slip line pattern depends sensitively on the orientation of the stress axis. Single slip on the crystals investigated is not observed. The slip occurs preferentially on planed of type {110}, but usually further slip planes of the 〈111〉 zone are also active. The slip band structure is discussed in terms of elementary slip processes.
The Fine Structure of Spots in Electron Diffraction Resulting from the Presence of Planar Interfaces and Dislocations. III. Domain Boundaries
Authors: Gevers R. , van Landuyt J. , Amelinckx S. 
Published: July 2007

AbstractThe fine structure of electron diffraction spots caused by the presence of domain boundaries (δ‐boundaries) is derived theoretically. The same method is used as in part I, namely the Fourier transforms of the transmitted and scattered intensities are calculated and discussed. The predicted fine structure consists in a fourfold splitting of the scattered as well as of the transmitted beams in a direction perpendicular to the interface. It is shown that the relative intensities and the spacing of the spots in this quadruplet are strongly influenced by the anomalous absorption and by parameters such as e.g. Δs and s. The effect of domain boundaries on the multiplicity and nature of the splitting is discussed. Finally the relation between the constituent beams and the fringe pattern visible in transmission electron microscopy at domain boundaries is analysed. Excellent agreement is found with the pattern characteristics previously derived from the analytical discussion of the transmitted and scattered intensities.
Optical Absorption Edge of AIN Single Crystals
Authors: Pastrňák J. , Roskovcová L. 
Published: July 2007

AbstractFrom measurements of the absorption coefficient of AIN single crystals the direct band gap values EG = (5.88 ± 0.05) eV and EG = (5.74 ± 0.05) eV for E ⟂ c and E ∥ c, respectively, are determined. The slow increase in the absorption coefficient at the low‐energy side of the direct gap is related to indirect transitions. The exact determination of the indirect gap is hindered by oxygen absorption bands at (4.53 ± 0.08) and (4.80 ± 0.08) eV.
Relation between Relaxation Time and Jump Frequencies for Zener Relaxation in Disordered F.C.C. Alloys
Authors: Haven Y. 
Published: July 2007

AbstractThe dissociation of pairs has been taken into account, in addition to a mere reorientation of pairs, to derive expressions for the relaxation times of Zener relaxation in disordered f.c.c. alloys. The results are 1/τ1 = (12 k1 + 12.74 k2) fR, 1/τ2 = (8k1 + 12.78 k2) fR for the Eg and T2g mode of relaxation, respectively. Here k1 and k2 are jump rates for non‐dissociating and dissociating atoms, respectively, and fR is a correlation factor.