bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of radiation defects in electron irradiated Hg1−xCdxTe crystals using positron annihilation
Authors: Voitsekhovskii A. V. , Kokhanenko A. P. , Petrov A. S. , Lilenko Yu. V. , Pogrebnyak A. D. 
Published: January 2007

AbstractThe electron characteristics of defects in the initial and electron irradiated Hg1−xCdxTe (2–3 MeV, 1018 cm−2, 300 K) crystals using the positron annihilation method have been investigated. The data of electric measurements are confirmed on connection of p‐type conductivity with vacancy defects of metal sublattice initial crystals Hg1−xCdxTe. An analysis of correlation curves of irradiated crystals has shown a possibility of formation of associations of initial defects and radiation damages of vacancy type during radiation process. The presence of narrow component on correlation curves in the region of small angles is associated with formation of positronium states localized in the region of radiation defect complex of vacancy type. Identification of positron‐sensitive defects with electrically active radiation induced ones has been carried out according to the results of isochronal annealing of irradiated crystals.
Sintering and crystallization of titanium‐containing lead borate glasses
Authors: Brauer G. , Boden G. , Hübert T. , Kirsch M. 
Published: January 2007

AbstractThe sintering and crystallization of glass powders with chemical composition 47 PbO—38 B2O3—15 TiO2 (mole %) was investigated under non‐isothermal conditions by shrinkage measurements, differential thermo‐analysis (DTA), X‐ray diffraction (XRD), dielectric measurement and positron annihilation (Doppler broadening). The correlation between changes of macroscopic properties and positron annihilation results recommends this method for the detection of structural changes in glasses.
A fluctuation mechanism of crystallization processes for the one‐component metallic melts
Authors: Chistyakov Yu. D. , Baikov Yu. A. , Akulionok M. V. 
Published: January 2007

AbstractIn given work a mechanism of spontaneous fluctuations of the „unlimited”︁ spectrum solid state particle concentrations acting in some monolayers of two‐phase transitional zone within the small supercoolings' region is considered. This mechanism is applied for some one‐component metallic macrosystems crystallizing from the supercooled melts. It is established that given mechanism in the case of macrosystems transforms into action of only one spontaneous fluctuation occuring in each monolayer of two‐phase transitional region as a result of which the solid state particle concentration becomes equal to nearly 1/2. It is shown that in this case within the small supercoolings' region given mechanism leads to so‐called normal law of crystallization connected with one‐component metallic macrosystems. In the particular scheme of mechanism presented an effective kinetic coefficient is estimated. In the vicinity of melting temperature for some metallic melts a comparison of theoretical and experimental data concerning the mean crystallization velocities has been fulfilled. In the case of spontaneous fluctuations of the „unlimited”︁ spectrum solid state particle concentrations two‐phase transitional zone's sizes do not have influence on the one‐component metallic melts' crystallization kinetics within the small supercoolings' region.
X‐ray diffraction studies of interdiffusion in InAs—GaAs powder blends
Authors: Černý R. , Valvoda V. , Voland U. , Deus P. , John M. 
Published: January 2007

AbstractInterdiffusion in the pseudobinary system InxGa1−xAs is investigated by means of X‐ray diffractometry of annealed powder blends. The interpretation of the experimental results by means both of the concentric spheres and concentric cubes model yields for In0.43Ga0.57As an activation energy of (5.39 ± 0.11) eV. This value shows that the diffusion mechanism could be a vacancy one as in the pure compounds. According to the lower atomic radius the Ga atoms within the temperature interval of 550–625 °C diffuse more easily than the In atoms.
Positron lifetime measurements in as‐grown and electron irradiated InSb
Authors: Sen Gupta A. , Moser P. , Corbel C. , Hautojärvi P. 
Published: January 2007

AbstractPositron lifetime in an as‐grown InSb crystal is measured to be 282 ± 2 ps. Irradiation by 3 MeV electrons at 20 K to the dose 4 × 1018 e−/cm2 increases the lifetime by 8 ps. The irradiation‐induced vacancy‐defects recover until 350 K with a sharper annealing stage at 250 K–350 K.
Positron annihilation study of defects and microheterogeneity of chalcogenide glassy semiconductors — chemical bonding in ge—se and some AVBVI systems
Authors: Shantarovich V. P. , Kevdina I. B. , Kobrin B. V. , Minaev V. S. 
Published: January 2007

AbstractRecently developed ideas on the mechanisms of positron annihilation in chalcogenide glassy semiconductors are used in studying chemical bonding of the AVBVI structures (A = As, B = S, Se, Te) and GeSe.
Positron annihilation in BaF2 crystals
Authors: Elefteriades C. A. , Chardalas M. , Dedoussis Sp. , Charalambous Stef. 
Published: January 2007

AbstractPositron lifetime measurements in BaF2 were performed in the temperature range 10 to 292 K. Three lifetime components were resolved, the third component having a very low intensity. The intensity of the second component increases between 12 and 80 K. For further increase of the temperature, up to 290 K, the intensity of this component falls from about 63% to 37%. An increased positronium formation probability is suggested for explaining this observation. Some alternative explanations are discussed, as well.
Peculiarities of pendellösung fringes in quartz monocrystals
Authors: Zargaryan Y. G. , Bezirganyan P. H. 
Published: January 2007

AbstractThe scattering of X‐rays in quartz monocrystals has been investigated. It has been discovered experimentally, that even for the thick quartz crystals, for which μt = 5, pendular bands can be obtained. The appearance of pendular bands depending on the crystal thickness, the reflecting plane families and the reflection order, was investigated as well.
High pressure phase transformation in MnS
Authors: Kraft A. , Greuling B. 
Published: January 2007

AbstractThe structural, optical and electrical behaviour of MnS under high pressure was investigated. For X‐ray investigations and optical observations a gasketed diamond anvil cell was used. Measurements of the electrical conductivity were performed in a Bridgman opposed‐anvil apparatus. A structural phase transition at 7.2 GPa from the cubic α‐phase (NaCl‐type) to the B16‐type structure (GeS‐type) was detected by X‐ray investigations and confirmed by optical observations. Measurements of the electrical conductivity showed a linear decreasing electrical gap energy in dependence on pressure.
Fluctuation theory of the one‐component and binary metallic melt's crystallization in the case of micro‐ and macro‐systems
Authors: Chistyakov Yu. D. , Baikov Yu. A. , Akulionok M. V. 
Published: January 2007

AbstractAll types of fluctuation mechanisms resulting in a normal kinetics of the one‐component and binary melt's crystallization within a small supercooling region for micro‐ and macro‐systems are systematized. Three principal mechanisms of spontaneous fluctuations acting in the monolayers of two‐phase transitional zone in the vicinity of melting temperature for one‐component metallic crystals and of the liquidus temperature for binary ones are described. The formulas of kinetic coefficients figuring in the normal law of crystallization conformably to one‐component and binary metallic micro‐ and macrosystems for all types of fluctuation mechanisms are presented. Some peculiarities of each fluctuation mechanism are presented. Some peculiarities of each fluctuation mechanism acting within a small supercooling region of the melt‐crystal micro‐ and macrosystems are pointed out. A comparison of theoretical and experimental data concerning the one‐component and binary melt's crystallization kinetics at some small supercoolings is presented.
Crystallization kinetics of lithium niobate films from limited volume of melt solution
Authors: Madoyan R. S. , Khachaturyan O. A. , Grigoryan S. G. , Gabrielyan A. I. 
Published: January 2007

AbstractThe growth kinetics of LiNbO3 films from a limited volume of melt solution is observed. We developed crystallization models describing the character of mass transfer in the liquid phase for isothermal and non‐isothermal epitaxy. Analytical expressions have been derived connecting the film thickness with the system growth parameters. The experimental values being in good agreement with the calculated ones.
Inference of system configurations on thickness homogeneity and lateral dopant distribution of MBE grown films
Authors: Wolf B. , Zehe A. 
Published: January 2007

AbstractThe common technique to produce film thickness homogeneity and composition uniformity across the wafer in MBE‐growth is a slow rotation of the substrate while growth proceeds. This however is not compatible with most in‐growth analysis techniques. In this paper it is demonstrated, that an optimum uniformity without rotation can be achieved by an optimized system configuration.
Tc anisotropy and texture of fine niobium wire and foil
Authors: Shamrai V. F. , Galperovich D. Ya. , Efimov Yu. V. , Korzhakova T. V. , Babareko A. A. , Grechkov V. I. , Savelyeva M. E. 
Published: January 2007

AbstractTexture of surface and inner layers of cold‐deformed (> 90%) niobium wire (diameter — 0.5 mm) and foil (thickness — 40 μm) was studied immediately after deformation followed by layer‐wise etching of near‐the‐surface layers and the annealing effect in 0.001 and 0.00001 Pa vacuum on texture was found. Axis and inner plane textures of cold‐deformed niobium wire and foil, respectively, are typical of bcc lattice metals. The surface layer of fine wire subjected to considerable cold deformation possesses so‐called cylindrical plane deformation texture {100}〈011〉 (main) and {111}〈011〉 (additional). Surface layer of high deformed niobium foils is characterized by the shear texture {110}〈001〉. Presence of delineated texture and its maintainance during annealing (with changing ratio of individual components) causes the Tc anisotropy in fine niobium materials. Tc anisotropy is caused by different orientations of magnetic fields and directions of currents used for measurements by resistive and inductive methods with respect to the directions of prefered crystallographic orientation of wire axis and foil plane. The Tc values of pure niobium wire and foil measured by the resistive method are 0.1–0.3 K higher than the standard (9.2–9.3 K).
Heterogeneous gas bubble formation during GaP solution growth
Authors: Nghi Nguyen Thanh 
Published: January 2007

AbstractThe gas bubble formation on seed surface, during growth of GaP crystals from the solution, is considered on the basis of the model for heterogeneous nucleation. It is shown that the bubble formation in this case could be a consequence of the interaction between gallium oxide, Ga2O3, and gallium generating gaseous gallium protoxide, Ga2O3, during heating. The size of the bubbles incorporated in the crystal depends on the kinetics of this reaction and the dissolution rate of Ga2O3 in liquid gallium. The values of forces that act on gaseous bubbles in the liquid zone are estimated. It is shown that the migration behaviour of these bubbles is mainly determined by Archimed and thermocapillary forces and depends on growth situations. The methods for avoiding bubble formation in GaP solution growth are suggested.
Numerical modelling of heat transfer in GaSb Czochralski crystal growth (CZ and LEC)
Authors: Böttcher K. , Krüger A. , Schleusener B. 
Published: January 2007

AbstractBy the hand of a system‐oriented steady‐state model of the GaSb crystal growth (CZ and LEC) the crystal‐melt interface, the heat losses due to cooling, and the required crucible temperatures are calculated as a response to the boundary conditions for temperature and heat flows, and to the chosen geometry. Of special interest is a phantom of an after‐heater influencing the cooling of the crystal.
Growth and spectral investigations of oxide laser crystals with Pr3+ ions
Authors: Butaeva T. I. , Ovanesyan K. L. , Petrosyan A. G. 
Published: January 2007

AbstractThe main types of inhomogeinity in rhombic aluminate crystals doped with Pr3+ ions arise from light scattering particles and lattice defects causing colour center formation under short wavelength radiation. It is shown that additional electron and hole traps (iron and praseodimium ions) change the direction of processes of charge carrier release and capture as compared with the case of pure crystals.
Crystal and molecular structure of 9‐vinyladenine
Authors: Scharfenberg‐Pfeiffer D. , Kretschmer R.‐G. , Hoffmann S. 
Published: January 2007

AbstractThe title compound 9‐vinyladenine crystallizes in the monoclinic space group C2/c with 16 molecules in the unit cell and the lattice parameters a = 13.682, b = 10.250, c = 21.674 Å, β = 97.72°. The crystal structure has been determined by direct methods and refined by full matrix least squares calculations up to the discrepancy factor R = 0.045.The two symmetry independent molecules differ in the orientation of the vinyl group relative to the adenine frame.
X‐ray powder diffraction investigations of solid solutions with limited miscibility in the KNO3NH4NO3H2O system at 298 K
Authors: Dejewska B. , Sędzimir A. 
Published: January 2007

AbstractThe measurements of crystal lattice parameters (a, b, c) were conducted and the volumes (v) of unit cells of solid solutions forming in the system KNO3NH4NO3H2O at 298 K were calculated. It was established that in this system at 298 K two series of solid solutions were formed: the mNH4NO3 · n(KNO3 · 2 NH4NO3) solid solution with the gap of miscibility and the kKNO3 · l(KNO3 · 2 NH4NO3) solid solution with one‐sided limited miscibility.
Interferential method for determining the inclination angle of molecules in plane‐parallel liquid crystalline layers
Authors: Opara T. , Baran J. W. , Żmija J. 
Published: January 2007

AbstractThe interferential method is presented for determining the inclination angle θ of molecules in homogeneously ordered plane‐parallel liquid crystalline layers. The essence of the method is the analysis of the changes in the layer transmission caused by the change in conditions of interference. The angle θ is calculated from the exact, explicit relation where from no limitations the size of the angle results. The measuring‐stand is described that enabled the method to be put into practice. The results for the PCB layer are presented by way of example.
Infrared optical characterization of epitaxial layer — substrate systems (I) theoretical relations
Authors: Riede V. , Neumann H. , Sobotta H. 
Published: January 2007

AbstractTheoretical relations are given for the transmittance and reflectance of an epitaxial layer substrate system with arbitrary absorption in both the layer and the substrate. Some peculiarities of the optical spectra of epitaxial layer‐substrate systems in the infrared spectral range are discussed. Methods are described for determining the thickness and the material parameters of both the epitaxial layer and the substrate.
Lattice plane imaging in ZTA ceramics
Authors: Woltersdorf J. , Pippel E. 
Published: January 2007

AbstractCharacteristic interface phenomena have been studied in zirconia toughened alumina (ZTA) using high‐resolution electron microscopy. Glassy phases in grain triple junctions, microstructure of interfaces between martensitic twins, regularly spaced misfit dislocations at the interface between intragranular t‐ZrO2 and the Al2O3 matrix and amorphization processes in the twin‐terminating region (which can initiate grain‐boundary microcracking) were observed by lattice plane imaging techniques.
Investigation of the nucleation kinetics and the linear growth rate during the devitrification of Fe‐B amorphous alloys with the aid of a thermomagnetic balance
Authors: Spassov T. , Budurov S. 
Published: January 2007

AbstractThe kinetics of overall isothermal crystallization of the amorphous Fe75B25 alloy, as well as the kinetics of nucleation and growth in amorphous Fe75B25 and Fe80B20 alloys were investigated with the aid of a thermomagnetic balance. The activation energies of growth for both alloys QG = 167 kJ/mol, which are similar to these, found by other authors, were determined. Curves number of nuclei N vs time t were traced and the activation energy of nucleation in the amorphous alloy Fe80B20 was obtained QN = 211 kJ/mol, which value is also in very good agreement with those determined by means of other independent methods.
Liquid crystalline swallow‐tailed compounds (III). Swallow‐tailed Compounds with Terminal Cyano Groups
Authors: Weissflog W. , Pelzl G. , Kresse H. , Demus D. 
Published: January 2007

AbstractA new homologous series of swallow‐tailed compounds possessing terminal cyano groups was synthesized. These substances form nematic phases with a relatively small negative dielectric anisotropy. In electric fields planar oriented samples of these compounds exhibit domain instabilities of different kind depending on the experimental conditions.
A new approach to the analysis of an adiabatic thermal stress in an ideally brittle solid under external mechanical perturbation
Authors: Majumdar B. , Dubey B. N. 
Published: January 2007

AbstractA new approach to the analysis of an adiabatic thermal stress is an ideally brittle solid under external mechanical stress is presented, when fracture occurs well before plastic yielding. An expression for the magnitude of the temperature drop ΔTf to start fracture in crystals of cubic shape have been deduced and analysed in terms of free energy, entropy, modulus of elasticity, and a new parameter termed as ‘resistance to brittle failure (α)’. It is found that the order of thermal shock resistance of brittle material depends largely on α and varies depending upon the particular characteristic of material.
Phase transitions in vitreous and amorphous SiO1
Authors: Gerber Th. , Himmel B. , Lorenz H. , Stachel D. 
Published: January 2007

AbstractAs a rule, glassy and amorphous solids are characterized by random, irregular structures. More recent examinations, however, indicated that even this group of materials possesses certain structural laws. Glassy and amorphous SiO2 samples were investigated using X‐ray diffraction. The results of this investigation can be interpreted as structural phase transitions. When subjected to a pressure‐temperature treatment (p = 7 GPa, T = 700 °C), a 15 per cent irreversible densification of vitreous silica without crystallization could be achieved. This can be interpreted as a reconstructive transformation of a certain topological structure (vitreous silica having a cristobalite topology) into another topological structure (densified vitreous silica having a quartz topology).Temperature‐dependent measurements of disperse SiO2 (porous glass, silica gels) led to the conclusion that a displacive phase transition (analogous to the α‐β‐transition in cristobalite) had taken place in the amorphous network.
On preparation and reactivity of partial‐crystalline aluminas
Authors: Bollmann U. , Becker K. , Berger H.‐J. , Birke P. , Engels S. , Gruhn G. , Jancke K. , Kraak P. , Lange R. , Steinike U. 
Published: January 2007

AbstractThe main part of this paper represents a comparison of the investigations of the gibbsite short‐time heat treatment with other calcination methods. The transition forms of alumina, preferentially nearly amorphous Al2O3and χ‐Al2O3, resp., produced by mechanical activation and short‐time heat treatment procedure show a very high reactivity and a large specific area. The samples can be transmitted into different aluminium hydroxides, particularly into boehmite‐rich products with a very low alkali content by hydration of alumina solids. These solids can be used preferentially for the preparation of adsorbents and catalyst components.
Process control of lateral autodoping in silicon epitaxy by measuring the sheet resistance
Authors: Kühne H. , Barth R. , Malze W. , Königsdörfer H. 
Published: January 2007

AbstractA particular test structure is presented the design of which has been based on several buried layers formed as circular rings with a suitably selected distance from each other. In an environment (concerning both substrate wafer and epitaxy layer) having an opposite type of (but low enough) conductivity with respect to buried layer, lateral autodoping will reveal a conducting channel between adjacent buried layers the sheet resistance of which can simply be measured. — It is shown that all those known effects influencing lateral autodoping as for instance buried layer doping level and substrate prebake can be revealed by sheet resistance measurement of the ring‐shaped test structure, which additionally can be applied to wafer mapping of lateral autodoping.
Liquid phase epitaxy of GaAs on Si substrates
Authors: Brovkin V. N. , Kazakov A. I. , Presnov V. A. 
Published: January 2007

AbstractThe possibility of epitaxial growth of GaAs on Si substrate using liquid phase epitaxy is shown. The investigation of substrate orientation influence upon nucleation and growth of GaAs exhibited that the more preferable orientation on Si substrate is (100). The peculiarities of GaAs growth on Si by eutectic LPE are explained by the formation of the different types of “growth units” in supersaturated liquid phase.
Gel growth of single crystals of α‐glycine, L‐threonine and N‐glycylglycine
Authors: Natarajan S. , Devadoss H. Alex , Alwan K. 
Published: January 2007

AbstractSingle crystals of α‐glycine, L‐threonine, and N‐glycylglycine were grown using silica gel as the medium of crystal growth. The reduction of solubility method was used for crystal growth. The effect of various acids mixed with the gel to obtain the particular pH on the growth of crystals was studied. The effect of different organic liquids used, to reduce the solubility of the substance, on the growth of crystals was also studied. The results show that the gel method could yield crystals of reasonable size and good quality in the case of the above substances. X‐ray studies have been made to characterize the substances.
Effect of annealing on the photoconductivity of CdS:Yb crystals
Authors: Bhushan S. , Sharma S. K. 
Published: January 2007

AbstractAnnealing in air produces less photocurrent and a small IPC/IDC ratio compared to those of unannealed CdS:Yb crystals. Annealing in sulfur makes the crystals very conducting without any increase due to photoexcitation. Annealing in presence of Cd metal makes the photo‐response quite fast. Results of photoconductivity excitation spectra are also presented and discussed.
Infrared Study of Proton Implanted GaP Single Crystals
Authors: Sobotta H. , Neumann H. , Riede V. , Ascheron C. , Nobes M. J. 
Published: January 2007

AbstractInfrared absorption spectra are measured for GaP single crystals implanted with protons of different energies and fluences. Besides a localized mode due to PH bond vibrations the samples exhibit a second mode at about 1840 cm−1 which is ascribed to GaH bond vibrations. The dependence of the integrated absorption A of this mode on the fluence D follows the relation A ∽ Dn with n = 0.52. The results obtained are compared with previous studies on proton implanted GaP, GaAs, InP and ZnSe.
Influence of impurity band conduction on the electrical characteristics of p‐type GaAs
Authors: Neumann H. 
Published: January 2007

AbstractThe contribution of impurity band conduction to the Hall coefficient and mobility is estimated for p‐type GaAs using existing experimental data for the hole mobility in the valence band and in acceptor impurity bands. It is found that impurity band conduction affects the measured electrical characteristics in the standard temperature range from 77 to 300 K usually used in materials characterization, if the acceptor concentration is above about 5 · 1017 cm−3.