bluuebunny/crossref_metadata_2025 huggingface dataset:
Solid‐state reactivity and mechanisms in oxide systems (IV) on the sintering behaviour of haematite
Authors: Pfaff G. , Feltz A. , Umpfenbach U.
Published: January 2007

The present contribution reports about the sintering behaviour of three α‐Fe2O3 powders which were synthesized in various ways. The different results of the sintering experiments are the consequence of granulometric properties of the samples and of their content of impurities. Possible sintering mechanisms are discussed.
Nonstoichiometry and point defects in PbTe
Authors: Schenk M. , Berger H. , Klimakow A. , Mühlberg M. , Wienecke M.
Published: January 2007

The nostoichiometry and point‐defect structure of PbTe was investigated by various methods including carrier‐concentration, lattice‐constant, positron‐annihilation and vapour‐density measurements. The results are discussed in comparison with data published by other authors. New aspects are obtained especially from high‐temperature experiments. A model of nonstoichiometry and defect structure in PbTe is proposed. The stability region of PbTe is essentially broader than reported until now. The disorder takes place mainly in the Pb sublattice, i.e., there occur charged Pb vacancies (Te‐rich) and Pb interstitials (Pb‐rich), respectively, as well as probably additional neutral Pb interstitials in Pb‐rich PbTe.
Simulation of the carrier diffusion process for the interpretation of EBIC profiles
Authors: Werner U. , Heydenreich J.
Published: January 2007

Based on a Monte Carlo calculation procedure a phenomenological description is developed of the diffusion process of excess minority charge carriers inside a semiconducting target. Using this description and an analytic expression of the generation volume of electron‐hole pairs in Si the electron beam induced current (EBIC) obtained by applying a scanning electron microscope can be simulated under consideration of relatively complicated structures of junction semiconductor devices. This allows a better interpretation of EBIC profiles as to the information about the geometric structure of space charge regions built up in junction semiconductor devices. As an example of such an interpretation the verification of the method of Chi and Gatos is presented.
X‐ray determination of solid solution composition in the melilite system åkermanite (Ak) — gehlenite (Ge) — soda melilite (Sm)
Authors: Schmitz W. , Schreiter P.
Published: January 2007

Expressions are given and discussed which allow a determination of the composition of solid solutions in the ternary system AkGeSm. Resulting from X‐ray measurements of the tetragonal melilite constants a0 and c0, the composition can be calculated within the limits of ±3% if the lattice constants are determined with an accuracy of ±0.001 Å.
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

The 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

The 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

In 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

Interdiffusion 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

Positron 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

Recently 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

Positron 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

The 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

The 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

All 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

The 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

The 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

Texture 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

The 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.
Tilt angle measurements in Sc phases by dielectric reorientation
Authors: Pelzl G.
Published: January 2007

For 7 SC materials the tilt angle was measured as function of the temperature. The measurements were carried out by means of a new electrooptical method based on the dielectric reorientation of planar oriented samples.
Numerical modelling of heat transfer in GaSb Czochralski crystal growth (CZ and LEC)
Authors: Böttcher K. , Krüger A. , Schleusener B.
Published: January 2007

By 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

The 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

The 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

The 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

The 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

Theoretical 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.
The permutations of lattice parameters and space group symbols of the orthorhombic PbCl2
Authors: Hybler J.
Published: January 2007

The space group notation of orthorhombic crystals in different permutations of unit cell axes are explained on the example of PbCl2.
Lattice plane imaging in ZTA ceramics
Authors: Woltersdorf J. , Pippel E.
Published: January 2007

Characteristic 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

The 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

A 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

A 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

As 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

The 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

A 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

The 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

Single 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

Annealing 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

Infrared 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

The 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.
Electrical properties of vacuum‐evaporated ZnTe films
Authors: Patel N. G.
Published: January 2007

ZnTe thin films were grown on glass substrates using vacuum evaporation technique. A cylindrical furnace is designed for substrate heating, which improve the crystallite size and stoichiometry over wide substrate temperature range. The variation of electrical resistivity and photosensitivity are explained on the basis of stoichiometric composition and improvement in the crystallite size of ZnTe films deposited at different substrate temperatures. The effect of films thickness variation on the electrical resistivity have been studied. Efforts of impurities doping in ZnTe films for improving the conductivity of ZnTe film are not successful on account of self‐compensation effect.
Some replica possibilities for electron‐microscope investigations of ice crystal morphology
Authors: Stoyanova V. , Genadiev N. , Nenow D.
Published: January 2007

Comparative SEM investigations have been carried out on small ice crystals by means of vapour and modified replica methods. Different replica solutions based on 3 polymers (formvar, plexiglass, polystyrene) and 3 organic solvents (methylene chloride, chloroform, ethylene dichloride) have been used. The conditions for accurate replication have been considered.
Tannic acid induced penetration twinning in gel‐grown calcium sulfate dihydrate
Authors: Cody R. D. , Cody A. M.
Published: January 2007

Well‐formed calcium sulfate dihydrate penetration twins with twin plane a(100) are induced by the presence of gallotannic acid under alkaline conditions in bentonite clay gel. These twin closely resemble natural gypsum that occurs in alkaline desert soils.
The origin of synthetic polycrystalline skeletal diamonds
Authors: Substyk M.
Published: January 2007

A reaction vessel for diamond production modified by using a graphite heater around a metal‐graphite sandwich set has changed the physical conditions (especially the thermal conditions) inside the set during the synthesis process. There has been built up a reduced radial temperature gradient, as compared to the gradient in a reaction vessel for repetition work. As an effect of the process polycrystals with very different shapes, morphology, and internal structure have been achieved, and they are named as skeletal polycrystals. Basing on the relation between crystal morphology and its growth conditions, in this paper a suggestion of this polycrystals' growth process is described. It is assumed that the principal driving force of polycrystals' growth process has been the supersaturation of the cobalt solution by graphite. As a result of diamond crystallization, the graphite content decreases and causes the change of growth mechanism from continuous growth through two‐dimensional nucleation to spiral growth. It is well noticed in the skeletal polycrystals' morphology.
Interdiffusion of Mn in austenitic and ferritic CrNi steels
Authors: Tariq M. , Bergner D.
Published: January 2007

The interdiffusion coefficients of Mn have been obtained in different austenitic and ferritic CrNi‐steels between 1000 and 1300 °C using Boltzmann‐Matano and Grube methods. The diffusion coefficients of Mn (≦ 2 wt%) were found to be independent on its concentration. Small variations in Cr and Ni contents in both types of steels showed neglegible effect on manganese diffusion. The interdiffusion results in austenitic steels are comparable with the Mn tracer diffusion in Type 316 steel. The results of diffusion of manganese in ferritic CrNi steels reported here are first to be published.
Bulk non‐radiative recombination reduction in nGaAs due to an annealing under Ga‐Al melt
Authors: Andreev V. M. , Salieva O. K. , Solov'ev V. A. , Sulima O. V. , Khammedov A. M.
Published: January 2007

It is shown by microcathodoluminescence and electron beam induced current investigations that efficiency of radiative recombination and the values of hole diffusion lengths in nGaAs substrate increase (up to Lp ∽ 5 μm) due to an annealing under GaAl melt. The values of the annealing critical temperature exceeding of which leeds to bulk non‐radiative recombination drop as well as optimal values of annealing temperature and duration are determined.

In pAlGaAs–(p‐n)GaAs solar cells based on annealed substrates the values of open circuit voltage Uoc = 1.16 – 1.18 V under 500‐fold concentrated solar radiation as well as values of photocurrent comparable with the best results of solar cells with epitaxial nGaAs are achieved.
The current understanding of epitaxial CVD silicon layer doping in the light of modeling and theory development (VII)
Authors: Kühne H. , Schröder K.‐W.
Published: January 2007

Extension and maximum concentration of autodoping profile are discussed for both lateral and vertical autodoping phenomena and, additionally, bearing in mind the typical course of autodoping profile as obtainable by spreading resistance technique, on the background of previously published theoretical concepts of dopant incorporation. It is shown that the “improved” (three‐step mechanism) as well as the “consequent” dopant incorporation concepts (two‐step mechanism) are suited for theoretically explaining autodoping phenomena. If no additional supposition will be stated, however, it is a consequence of the former that the concentration maximum in the profile of vertical autodoping equals the buried‐layer surface dopant concentration in agreement with non‐steady state layer doping behaviour after dopant source flow has been immediately interrupted. In the contrary the latter conception simply identifies lateral and vertical autodoping effect since autodoping above as well as beyond buried layer is controlled in the same way by parasitie dopant partial pressure in the gas.
Mass spectrometric studies of adsorption of silver on tungsten (110) surfaces
Authors: Gerth G. , Abelmann U.
Published: January 2007

The adsorption of silver on (110)tungsten was studied by a mass spectrometric molecular beam technique. The temporal behaviour of the flux of adatoms leaving the substrate was measured at fixed temperatures between 860 K and 1080 K for constant impinging rates over the range 0.2 · 1013 to 9.0 · 1013 cm−2 s−1.

For moderate supersaturation the growth mode changed from the layer‐by‐layer growth of three monolayers to the growth of three‐dimensional nuclei (Stranski‐Krastanov mechanism). At equal rates of impinging and desorption flux, the equilibrium adatom concentration was determined and a set of adsorption isotherms was thus derived. The shape of the experimental isotherms was found to be broadly similar to that of the theoretical Fowler‐Guggenheim isotherm for a localized adsorption model. The binding energy of an Ag atom to the substrate, the lateral binding energy of a pair of atoms, the coordination number, and the vibration frequency of the adatoms for all three monolayers were obtained by suitable fitting procedures.
Growth and basic dielectric data of high quality TSCC crystals
Authors: Vaněk P. , Klöpperpieper A. , Albers J.
Published: January 2007

Tris‐sarcosine calcium chloride (TSCC) single crystals were grown from water solutions by the isothermal evaporation method. The growth solutions contained sarcosine and CaCl2 either in stoichiometric or nonstoichiometric ratio. The required phase diagram sarcosine–CaCl2H2O at 40 °C was determined by the synthetic method. PFT 400 MHz NMR was used for the analysis of organic impurities in sarcosine and TSCC. The crystals grown from both types of solutions had maximum values of the dielectric permittivity 10 to 200 times larger than those measured by other authors at comparable measuring frequencies and fields. It is discussed in terms of crystal quality.
Electrooptical investigations on a nematic two frequency addressing mixture
Authors: Stettin H. , Kresse H. , Demus D.
Published: January 2007

The change of the sign of the dielectric anisotropy of a nematic liquid crystal allows an active switching process in electrooptical cells in on and off direction. In the two frequency addressing mode the TN cell shows a qualitative and quantitative different dynamic behaviour in comparison to the conventional driving mode. During the switching on process hydrodynamical domains occur. After switching off the director configuration skips into the −3π/2 twist and thereby it realizes a loss in transmission. The director configuration relaxes into the quarter twist after some minutes. A superposition of low frequent and high frequent voltage gives a strong increase of the number of multiplexable lines.
Problem of multiple solutions in the Taylor model
Authors: Wierzbanowski K.
Published: January 2007

The Taylor model of polycrystal plasticity gives multiple solutions for some crystal orientations. This means that the slip systems, slip shears and crystal rotations are not unique. In such a case the unique prediction of crystal rotation is impossible and consequently some limitations for the texture study are imposed. We propose to eliminate this degeneration using an energetic criterion based on the anisotropic latent hardening of slip systems. We present a few examples of unique choice of slip systems and of crystal rotation.
Zeolite NaCaA as a desulphurization adsorbent – modification of its thermal and hydrothermal stability
Authors: Lutz W. , Bülow M. , Feoktistova N. N. , Vtjurina L. B. , Shdanov S. P. , Siegel H.
Published: January 2007

The thermal and hydrothermal stability of the zeolite NaCaA in dependence on the ion exchange degree have been investigated. The increasing thermal stability of the zeolite with increasing content of calcium ions corresponds to the higher stability of calcium silicates compared with sodium silicates. In contrast to that the decreasing hydrothermal stability is due to the decreasing alkalinity of the zeolite in aqueous media. Measurements of the pH‐value of zeolite/water slurries underline this tendency.
The influence of controlled electron‐seeking addition agents of the melt on stilbene single crystal structure and radioluminescence properties
Authors: Krainov I. P. , Galunov N. Z. , Budakovsky S. V.
Published: January 2007

The study of certain radioluminescence characteristics of stilbene single crystals is performed. Doping the stilbene melt with electron‐seeking (ES) addition agents of benzol and benzophenone halogen derivatives allowed to control the structure perfection of the crystal grown. The root‐mean‐square random orientation of single crystal mosaic structure, and concentration of the deep traps of charge carriers and excitons were minimum for the single crystals grown from the melt containing 0.1 mol% ES addition agent. Doping the melt with ES addition agents did not cause the appearance of additional luminescence impurity centres or quench luminescence centres in the single crystals grown.
Infrared optical properties and crystal structure of Cu2GeS3
Authors: Neumann H. , Riede V. , Sharif N. , Sobotta H. , Omar M. S.
Published: January 2007

Infrared reflectivity and transmission spectra of Cu2GeS3 are measured at room temperature in the wavenumber range from 180 to 4000 cm−1. From an analysis of the spectra the parameters of the fundamental infrared active lattice modes and of the two‐phonon combination modes are determined. From a comparison of the experimental data with group theoretical predictions for the structure models proposed for Cu2GeS3 in the literature it is concluded that Cu2GeS3 crystallizes in a monoclinic lattice.
Hydrothermal synthesis of (Zr0.33 Ti0.67) O2–srilankite in the system ZrO2TiO2H2OMF; (M = Na, K)
Authors: Buhl J.‐Chr. , Willgallis A.
Published: January 2007

The hydrothermal synthesis in the system ZrO2TiO2H2OMF; (M = Na, K) is discussed for the temperature range 573 K–773 K and the pressure of 100 MPa to 150 MPa. Starting with Zr‐ and Ti‐ butoxides their co‐precipitated hydrolysates which had been annealed in different ways were used as initial products. The formation of mixed crystals (Zr, Ti)O2 analogous to the rare mineral srilankite was dependent on the crystallinity and homogeneity of the initial products. 573 K and 100 MPa proved to be the most favourable conditions for synthesis. Higher temperatures (773 K) produced multiphase crystallizates of (Zr, Ti)O2, baddeleyite, anatas, and rutile.
MOCVD layer growth of ZnO using adducts of dimethyl‐ and diethylzinc
Authors: Kaufmann Th. , Fuchs G. , Webert M. , Frieske S. , Gäckle M.
Published: January 2007

Reaction mixtures of the tetrahydrofuran adducts of Zn(CH3)2 and Zn(C2H5)2 with tertiary butanol are very well suitable for the MOCVD of c‐axis oriented ZnO films. The deposition process is greatly determined by the kind of the gas inlet into the vertical reactor. The growth rates present a great dependence on temperature. The incorporation of compensating copper acceptors can be achieved with the help of cyclopentadienyl (tributylphosphine)‐copper (I). The structural and the electrical properties of the films are presented.
Infrared lattice vibrations in CuGe2P3
Authors: Neumann H. , Sharif N. , Riede V. , Omar M. S. , Sobotta H.
Published: January 2007

Infrared reflectivity spectra of CuGe2P3 single crystals are measured at room temperature in the wavenumber range from 180 to 4000 cm−1. From an analysis of the spectra the parameters of five vibrational modes are determined. The results are discussed in terms of the Keating model and are compared with lattice vibrational data for ZnGeP2, CdGeP2, and CuSi2P3.
The coprecipitation of magnesium aluminium hydroxocarbonate powders from aqueous solution: Precipitate compositions and coprecipitation mechanisms
Authors: Packter A. , Panesar K. S.
Published: January 2007

Magnesium aluminium hydroxocarbonate hydrates were coprecipitated from mixed metal nitrate solutions, at total CM = 0.2 M and Mg/Al2 = 1 ratio, with four sodium hydrogen carbonate‐sodium carbonate solutions (of pH 8.1 to 11.5) at ambient temperature. The course of precipitation was monitored by potentiometric (pH) titration, and the compositions of the primary and final precipitates were determined by chemical analysis, infrared spectrophotometry and X‐ray diffraction.

Precipitation generally occurred through three stages, primary precipitation (of low CO3 aluminium hydroxocarbonates) at low pH with evolution of carbon dioxide, their dissolution by complexing to form hydroxocarbonatoaluminate anions and then secondary precipitation of the final coprecipitate at higher pHs. The final product from coprecipitation by sodium hydrogen carbonate solution (pH 8.1) was mainly the magnesium hydroxocarbonatoaluminate ‘MAHC I’; the final products from coprecipitation by sodium hydrogen carbonate‐sodium carbonate solutions (pH 9.4 and 10.3) were ‘MAHC I’/‘MAHC II’ mixture and ‘MAHC II’/‘MAHC I’ mixture whereas the final product from coprecipitation by sodium carbonate solution (pH 11.5) was a complex mixture if ‘MAHC II’ with ‘MAHC I’ and ‘MAHC III’;

‘MAHC I’ was probably Mg2[Al4(OH)10(CO3)3] · hH2O,

‘MAHC II’ was probably Mg[Al2(OH)4(CO3)2] · h H2O whereas

‘MAHC III’ was probably Mg[Al2(OH)6CO3] · h H2O.
Properties of Ni/p–InTe Schottky barrier
Authors: Rousina Roughieh , Shivakumar G. K.
Published: January 2007

Nickel–indium telluride schottky barriers have been prepared by sequential evaporation, and their electrical characteristics have been studied. Various diode parameters have been obtained through current‐voltage and capacitance‐voltage characteristics. An equilibrium energy level diagram for the Ni/p–InTe system has been constructed using the experimental results.
The transition layers in AlGaAs/GaAs and InGaAsP/GaAs heterostructures grown by LPE
Authors: Bolkhovityanov Yu. B.
Published: January 2007

AlGaAs/GaAs and InGaAsP/GaAs heterostructues were grown by liquid phase epitaxy (To = 800–770 °C), the transition layers (TLs) were measured with Auger profiling. The Auger profiling of the InGaAsP/GaAs heterostructures after a long heating (1–6 hours, 770 °C) has been made too. The analysis of the experimental data led to the conclusion that the fundamental values of the TL in above mentioned systems are about 10 and 1 to 2 nm, correspondingly. This difference between the minimum widths of the TL in AlGaAs/GaAs and InGaAsP/GaAs system is connected with the different speed of solid state diffusional processes which occur at the initial stpeps of liquid – solid contact.
Theoretical compton scattering profile for conduction electrons in lithium
Authors: Mosharafa A. A.
Published: January 2007

The theoretical Compton scattering profile of the conduction electrons in lithium is calculated for three scattering vectors, taken along the symmetry axes of the Brillouin Zone. Qualitatively, the results are in good agreament with experiment, however, quantitatively, there are some discrepancies which are probably due to correlation effects. It is desirable to have more refined experimental data.
Computer analysis of regularities of nucleation and crystal growth in a solid
Authors: Larikov L. N. , Karpovich V. V. , Dneprenko V. N.
Published: January 2007

An interplay between the homogeneous nucleation and growth processes during recrystallization and phase first‐kind transformation was investigated. Computer simulation taking account of unsteadility of nucleation process and possibility of elimination of potential nucleation sites at a constant growth rate allowed to obtain the time dependence of nucleation rate of the new phase, Ṅ, in the total bulk of a sample. The various kinds of the dependence Ṅ including an increase, a constancy and a decrease are obtained.
Analytical calculation of binding energies of highly symmetrical particles
Authors: Fritsche H. G.
Published: January 2007

Analytical formulae of binding energies per atom are derived for icosahedral, cuboctahedral and face‐centered cubic particles AN by means of summation of pair potentials. Asymptotical relations for larger particles E/N = V (A – BN−1/3) as well as the topological model of clusters are discussed.
The thermal expansion of microcracks and grain boundaries in crystals (I). A new mechanism of crack formation
Authors: Vlasov A. D.
Published: January 2007

Apart from known reasons for crack formation it may be effected by the spontaneous microcrack wall heating. This heating takes place because of crack widening and formation of relatively free surfaces (crack walls). These surfaces must have the effective temperature that is well above the temperature in the bulk of crystals, as it has been shown earlier by the author. Simple equations for the thermal expansion of microcracks had been suggested. It has been shown that at the temperature above of 0.9Tm (Tm is the melting point) for the pure metals the spontaneous, without external stresses, crack formation takes place that may cause creep and superplasticity proceeding by the diffusion mechanism. At Tm the spontaneous cracking results in the crystal crushing to the microcrystallites, that is the spontaneous cracking may be considered to be the melting mechanism. From this point of view the intensive thermal expansion of liquids in temperature range from Tm to the critical temperature involves mainly the enlargement of microcrystallite gaps. By using this supposition simple equations for thermal expansion of liquids have been proposed.
Crystal growth of Ca3−xYxMn2Ge3O12 and phase relations in the PbOB2O3GeO2 based melts
Authors: Nevřiva M. , Durčok S. , Pollert E.
Published: January 2007

The bulk crystals of Ca3−xYxMn2Ge3O12 garnets were grown on a seed from the PbOB2O3GeO2 based melts, where the primary crystallization field of garnets was found. The saturation temperatures of the melts were determined before each growth run. The dependence of Y incorporation into the crystals versus the melt composition was also evaluated.
Impurity distribution within the diffusion layer in the cluster crystallization model
Authors: Zharikov E. V. , Zavartsev Yu. D. , Laptev V. V. , Samoilova S. A.
Published: January 2007

The impurity distribution in front of the surface of the growing crystal by Czochralski method is considered at the assumption that the crystallization begins in the melt within the diffusion layer by the formation of clusters, i.e. it has an extented nature. The moving force of the crystallization is the supercooling of the melt. The principle distinction from the classical BPS theory is that the concentration profile has no break near the meltcrystal interface and is defined by the impurity concentrations both in the liquid and cluster phases with allowance for their specific volumes.
Effects of melt composition on structural and electrical characteristics of LEC Si‐doped gallium arsenide
Authors: Fornari R.
Published: January 2007

The aim of this paper is that of briefly reviewing the experimental observations carried out on Si‐doped gallium arsenide grown from off‐stoichiometry melts (either Ga‐ or Asrich) in the author's laboratory. It will be shown that the melt composition strongly affect the electrical (electron mobility, density of deep levels) and structural (dislocation density, precipitates) properties of the bulk crystals which proves the existence of a link between point defects and physical and crystallographic characteristics. The experimental results will be discussed considering recent literature reports on point defects in bulk GaAs.