bluuebunny/crossref_metadata_2025 huggingface dataset:
X‐ray investigation of the mechanism of phase transformation in single crystals of ZnS, ZnxCd1−xS and ZnxMn1−xS (I). Calculation of diffraction effects by a three parameter model
Authors: Sebastian M. T. , Krishna P.
Published: January 2007

Hexagonal close‐packed (2H) single crystals of ZnS, ZnxCd1−xS and ZnxMn1−xS are known to undergo solid state transformation to the cubic close‐packed (3C) and 6H‐structures on annealing at elevated temperatures. The transformations occur by the non‐random nucleation of stacking faults on individual close‐packed layers parallel to (0001). The nature of the faults involved and their probability distribution during transformation determine the diffraction effects produced along the 10. L reciprocal lattice row by a crystal quenched in an intermediate state of transformation. We have investigated the mechanism of the transformation by comparing the diffraction effects recorded from such crystals on a single crystal diffractometer, with those calculated for an assumed model of the transformation.

It is known that in these materials the faults involved in the transformation are deformation faults. To explain the observed diffraction effects we develop a three parameter theoretical model employing a fult probability α for the radom insertion of a deformation fault in the 2H structure, a fault probability β for the deformation faults to occur at three layer separations and a fault probability γ of their occcurrence at 2‐layer separations. The probability α corresponds to the development of a fresh nucleus, the probability β to the growth of the 6H nucleus and the probability γ to the growth of a 3C nucleus. This paper develops the necessary theory of X‐ray scattering for such a model of the transformation and predicts the diffraction effects for different values of α, β, and γ. The next paper compares these results with experimental observations.
Simulation of contrasts in X‐ray plane wave topographs of quartz crystals with induced growth striations
Authors: Härtwig J. , Jäckel K.‐H. , Lerche V.
Published: January 2007

Using system theoretical methods and fast discrete Fourier transforms, contrasts in plane wave topographs of crystals with impurity distributions of any form can be simulated with high accuracy and in a short time.
The current understanding of epitaxial CVD silicon layer doping in the light of modelling and theory development (V). Special features of doping with arsenic in the range of small layer growth rates
Authors: Kühne H. , Morgenstern Th.
Published: January 2007

In the SiH4‐HCl‐AsH3‐H2 system of depositing epitaxial silicon doped with arsenic an equilibrium‐like doping process has been obtained by way of experiments not only as a limiting case at high deposition temperatures, as had been shown formerly, but also in the range of lower temperatures when the layer growth rate falls below a critical value. By means of introducing the term of a critical rate the theory of dopant incorporation, published in the Parts I–IV of the present report, has been extended to full completeness.
Incorporation of nitrogen into galliumarsenide grown by chloride VPE
Authors: Schwetlick S. , Seifert W. , Butter E. , Hörig W. , Pickenhain R. , Schwabe R.
Published: January 2007

The incorporation of nitrogen into GaAs in the halide‐VPE system using NH3 as the doping source is investigated. The concentration of incorporated N depends on the NH3 flow rate and increases with decreasing deposition temperature. Concentrations up to 6 × 1017 cm−3 could be detected far above the calculated equilibrium value.

By a comparison of SIMS‐data with those obtained from IR it is found that most of the N‐atoms are situated substitutionally on As lattice sites.

Normal‐pressure 2 K photoluminescence measurements show N‐related luminescence peaks at 1.508 and 1.496 eV. Most probably this luminescence arises from complexes of N with undeliberately introduced impurities. For the 1.508 eV center a complex SiGa‐NAs is discussed. — A new N‐related metastable deep center with the energy levels Ec‐0.33, Ec‐0.41, and Ec‐0.68 eV could be found by DLTS.
X‐ray determination of the polarity of zincblende‐structure crystals
Authors: Berger H.
Published: January 2007

An X‐ray diffraction procedure for the determination of the polarity of noncentrosymmetric crystals by measuring the integrated reflections of opposite polarity on one surface of the crystal is described. The observed intensities must be corrected for the different asymmetries of the two reflections. To estimate the influence of crystal perfection on the correction factor, the ratios of the integrated reflections were calculated numerically for dynamic diffraction. The method has been applied for determining the polarity of CdTe.
Crystal growth in an improved bridgman variable shape graphite furnace
Authors: Nicoarǎ Irina , Nicoarǎ D. , Aczel Otto
Published: January 2007

An improved Bridgman‐type crystal growth system is presented. By using a new type of heaters, fluoride single crystals with a diameter up to 50 mm and 150 mm length have been obtained. The dislocation density distribution has been examined in different growth conditions.
Photoconductivity of (ZnS, CdSe): Dy
Authors: Bhushan S. , Giriya L. C.
Published: January 2007

Photoconductivity rise and decay curves have been investigated for (ZnS, CdSe): Dy as a function of flux concentration, concentration of Dy, applied voltage, atmosphere during preparation and different excitation intensities. Substitution of Dy increases the photocurrent by five times. Maximum photocurrent is also observed at a particular concentration of flux. The decay is of hyperbolic nature and the trap depths are found at depths 0.49 eV and 0.54 eV which depend upon the concentration of Dy.
Influence of mixing on batch precipitation
Authors: Söhnel O. , Mullin J. W.
Published: January 2007

The influence of mixing on the induction period of batch precipitation of Ag2WO4, CaWO4 and SrWO4, in the supersaturation ranges 3.7–7.8, 32–134 and 121–210 respectively, has been studied at 25 °C. Increasing the intensity of mixing invariably decreases the induction period in all three systems. This effect in absolute terms is more pronounced at the lower supersaturations than at the higher.
Polymorphous transformation of quartz induced by mechanical treatment
Authors: Steinike U. , Uecker D.‐Chr. , Sigrist K. , Plötner W. , Köhler Th.
Published: January 2007

Because of its strongly damaged structure (partially crystalline) mechanically activated α‐quartz is not transformed to β‐quartz. Rather, mechanically activated α‐quartz is rapidly transformed to the cristobalite modification even at temperatures as low as 1200 °C. The acceleration and temperature shift of the quartz‐cristobalite transformation is caused by mechanically induced defects. The activation energy of the transformation is thus reduced by about 50%.
Gross dissolution of natural rhombohedral calcite crystal in nitric acid
Authors: Mehta B. J. , Sidpara G. R.
Published: January 2007

Gross dissolution of natural calcite crystal in concentrated nitric acid give interesting results. The gross dissolution is maximum at 6 M concentration of HNO3. The activation energy increases as the concentration of HNO3 increases. Similarly pre‐exponential factor is also increases as concentration increases. The combined effect of activation energy and pre‐exponentail factor gives the peak at 6 M concentration of nitric acid.
On the surface mechanism of crystal melting
Authors: Vlasov A. D.
Published: January 2007

A crystal melting mechanism is proposed. The melting is caused by enhanced thermal expansion of the lattice on the surface and around structure defects. For the microcrystallites formed this way an approximate calculation of parameters is made. The microcrystallites surface area per mole is shown to be thousands of m2, the radius within 1.5 to 10 nm, the gaps between microcrystallites — by 30 percent more than the lattice interatomic distance. The mean thermal linear expansion coefficients determined on the crystal surface are roughly ten times as much as the bulk values.
Helical structure and threshold voltage of cholesteric‐nematic phase change at different anchoring conditions
Authors: Hauck G. , Koswig H. D.
Published: January 2007

The helical structure of cholesteric mixed systems and their electro‐optical behaviour are studied at planar and pretilted surface orientation. The results indicate that the influence of the forces of wall orientation is decreased by the helical structure. To prove this model strong and weak anchoring conditions of the molecules in the cholesteric mixture at the substrate surface are realized. Also the behaviour of the electro‐optical threshold voltage at different surface conditions supports the assumptions concerning the helical structure.
Surface morphology and quality of potassium bichromate crystals obtained from aqueous solutions in relation to growth conditions
Authors: Szurgot M. , Sangwal K.
Published: January 2007

The characteristics of macrospiral layers on growth surfaces of potassium bichromate crystals and their quality are examined in relation to growth conditions. It was observed that the layers become thick and rounded, more inclusions are trapped and the crystal quality deteriorates with an increase in supersaturation, while an opposite effect is noted with an increase in growth temperature. The observations are discussed from the standpoint of crystal growth theories.
Specific heats of FCC solid solutions of the Bi2O3‐Y2O3 system
Authors: Berezovskaya Yu. , Budurov S. , Spasov T.
Published: January 2007

For the first time specific heats of the face centered cubic solid solutions (Bi2O3)1−x(Y2O3)x in the temperature range 350–1000 K were measured by means of Differential Scanning Calorimetry. Samples were also investigated with thermal expansion. The results showed the phase transitions for (Bi2O3)0.75 (Y2O3)0.25, which is acsribed to δ → δ* change in lattice mentioned in literature and for (Bi2O3)0.58(Y2O3)0.42, which is connected with a metastable behaviour of this sample.
Precision measurement of lattice parameters in LiF monocrystals
Authors: Dressler L. , Griebner U. , Kittner R.
Published: January 2007

The methodic possibilities of measurements by the Bond‐method for a highly precise determination of the lattice parameters in block structures with small block desorientation angles in the region of angular seconds or angular minutes (LiF crystals) have been examined. The lattice distorsion in two planes perpendicular to the (001) surface of crystalis described. The same planes have also been examined by elastooptic methods. In both planes we got for the lattice parameters: a1 & a2 > a3 (a1 and a2 parallel to the surface of crystal, a3 perpendicular to the surface of crystal); i.e. we could observe a dilatation of the unit cell parallel to the surface of the crystal. Special results concerning the distribution of local lattice parameters along the surface of sample are discussed in connection with the results of elastooptic observations.
Growth of crystals of calcium sulphate in silica gel in presence of additive and their characterisation
Authors: Kumareson P. , Devanarayanan S.
Published: January 2007

Procedure for the growth of calcium sulphate dihydrate crystals in silica gel, in the presence of barium chloride as additive, is described. Optimum conditions for the growth of good quality crystals are worked out. The crystals are characterised by laser Raman spectroscopy, infrared spectroscopy, thermogravimetric analysis and Atomic absorption spectroscopy. It is shown that crystals in the presence of the additive have a greater degree of perfection than those without additive. Amount of water in the crystals is estimated as 20.97%. Presence of calcium and absence of barium in the crystals are indicated.
Depth profile of the microhardness in helium implanted GaP
Authors: Ascheron C. , Neumann H.
Published: January 2007

Depth profiles of the damage density and the microhardness are measured in GaP single crystals implanted with 1 MeV helium ions. From an analysis of the experimental data it follows that the microhardness increases up to a damage density of about 16% due to point defect hardening. At higher damage densities the microhardness decreases rapidly, probably due to the formation of extended defects.
Slip band formation during bending of gap wafers
Authors: Jurkschat K. , Wagner G. , Paufler P.
Published: January 2007

{001} LEC‐GaP:S wafers were deformed between 470 °C and 640 °C. {111} slip planes of maximum resolved shear stress were activated. Heights and densities of slip steps have been measured by optical and electron microscopy. At lower temperatures deformation proceeds mainly by growth of step heights whereas at higher temperatures bending is accomplished by the increase of slip band density rather than of height.
Revealing of lattice defects on (111) faces of gallium phosphide and indium phosphide by chemical etching
Authors: Wagner G. , Gottschalch V.
Published: January 2007

A solution is presented suitable for revealing lattice defects on (111) phosphorous faces of GaP and InP. It is possible to distinguish between pits originated by grown‐in dislocations and microdefects such as perfect loops, faulted loops and precipitates and/or inclusions. Moreover it is also possible to reveal large stacking faults of Shockley type and microtwin lamellae. One to one correlations have been given by means of transmission electron microscopy.
Lattice constants and site preference in the system Ni2SiO4—Co2SiO4
Authors: Zahn A. , Schreiter P.
Published: January 2007

Most important supposition for a possible site preference in a olivine solid‐solutions are besides the different crystal chemical properties of M cations (size, electronegativity, crystal field stabilization energy) the differences between the both octahedral coordinated sites M1 and M2 of the olivine structure. Using this regularities the site preference in the system NiCo olivines is predicted. If site preferences are existing, it is possible to deduce deviations of the Vegard's rule in the system Ni2SiO4—Co2SiO4 using geometrically‐structurally considerations. The plot of experimentally determined lattice parameters in this solid solutions system shows the existing of the proposed deviations of the Vegard's rule and evidences the site preferences of Ni2+ in the M1‐ and Co2+ in the M2 octahedra only by determination of lattice parameters.
Calculation of one‐dimensional temperatures profiles in a crystal growth furnace with special respect to germanium
Authors: Buhrig E. , Hein K. , Walter G. , Geidel B.
Published: January 2007

In the paper a one‐dimensional method of calculation for temperature profiles in crystal growth furnaces is described. It is characterized by high flexibility. The model applied to our own calculations is based on heat balances in segments of a multi‐zone furnace and presupposes the availability of experimental data which allow the coefficients to be derived which are necessary to carry out the calculations. — The results of numerical calculations demonstrate the applicability of an existing furnace unit to directional crystallization of germanium.
Liquid crystalline swallow‐tailed compounds (II) dielectric relaxation
Authors: Kresse H. , Rabenstein P. , Stettin H. , Diele S. , Demus D. , Weissflog W.
Published: January 2007

Dielectric investigations in the kHz‐range on swallow‐tailed liquid crystals show a strong decrease of the dielectric constant as well as of the dielectric loss parallel to the nematic director with decreasing temperature. In the perpendicular direction no strong anomaly has been observed. By consideration of X‐ray data of the SA phase the dielectric results can be interpreted by the dipole‐dipole interaction which is forced by the anisotropy of repulsive forces of the respective molecules.
X‐ray topographic study of GaSb substrates for epitaxial layer growth
Authors: Vassilev I. S. , Pramatarova L. D. , Baeva M. B.
Published: January 2007

The depth of the layer damaged by silicing of GaSb ingots has been determined by X‐ray topography. The changes in the defect structure of substrates after successive etching to different depths by Br2/CH3OH and 1 HF:3 NNO3:1 CH3COOH have been studied. The effect of heat treatment carried out under conditions similar to the epitaxial process of substrates with completely removed damaged layer has been investigated.
Recent advances in the theory of crystal growth in silica gel medium
Authors: Desai C. C.
Published: January 2007

Growth of single crystal materials by slow diffusion process in a silica‐gel medium has been used for a long time as the method of simulation of natural processes in the laboratory. Recent advances in the theory of crystal growth have been described. The suitable theory of nucleation has been developed. Attention has been paid mainly to the more general case in which the counter diffusion of two reacting materials occurs. The implications are discussed.
Positron lifetime studies of organic coatings
Authors: Süvegh K. , Szeles Cs. , White M. L. , Vértes A. , Leidheister H.
Published: January 2007

Positron implantation and annihilation and the influence of water exposure on the annihilation properties were studied in a number of organic coatings deposited on metal substrates. Change of the lifetime spectra upon water exposure was related to the corrosion protective properties of the coatings.
Positron lifetime in mordenite
Authors: Ch. Abbé J. , Dębowska M.
Published: January 2007

Positron lifetime spectra have been measured for mordenite pure and impregnated with various amounts of metallic gold being highly dispersed. The change of annihilation characteristics (in comparison to those corresponding to the pure mordenite), resulting both from the presence of gold particles in the zeolite matrix and the way of treatment of the zeolite during the impregnation, has been noticed.
Nickel complexes of 1,10‐phenanthroline and 2,2′‐bipyridyl with strong intermolecular interactions
Authors: Oza A. T.
Published: January 2007

Nickel complexes of 1,10‐phenanthroline and 2,2′‐bipyridyl which can have strong intermolecular interactions have been prepared in the present work. The complexes with intermolecular interactions appear pink, red or red‐violet. Two of the complexes prepared Ni(Bip)2 · Ni(CN)4 · x H2O and Ni(Phen)2 · Ni(CN)4 · y H2O indeed show strong absorption bands at 470 nm and 500 nm, respectively.
Positron annihilation in GaAs
Authors: Misheva M. , Mishev P. , Pasajov G. , Toumbev G. , Yakimova R.
Published: January 2007

Positron lifetimes and three‐gamma annihilation in In, Cr, Te, and Sn doped GaAs have been measured. The mean τm and the bulk τb lifetimes in SI crystals are approximately 10 ps shorter than in n‐type crystals. Three‐gamma annihilation shows positronium formation in Bridgman grown samples only.
Positron lifetime study of hafnium nitride films
Authors: Brunner J. , Perry A. J.
Published: January 2007

Films of HfN can have expanded lattices which are restored by tempering, reflecting the presence of a high concentration of defects. The present study was made to get a qualitative understanding of the lattice relaxation on an atomic scale. The results support the proposal that the dominant mechanism is the migration of interstitial atoms into lattice vacancies.
Identification of predominant point defects in nonstoichiometric CuInse2 by X‐ray powder diffraction
Authors: Zahn G. , Paufler P.
Published: January 2007

Refinement of structural parameter, occupancy factors and temperature factors of three indium rich samples enabled type and concentration of intrinsic point defects to be determined. Vacancies on copper and indium sites (8 and 5%, respectively) and indium atoms on copper sites (5%) were identified. Indium atoms exhibit a large thermal vibration amplitude.
On the change of low‐temperature thermal conductivity of gap after bending
Authors: Zahn G. , Merisov B. A. , Klöss G. , Ya. Khadshaj G. , Müller S. , Gavrenko O. A. , Paufler P.
Published: January 2007

The thermal conduction of a sulphur‐doped single crystal plastically deformed by bending at 963 K was measured between 2 and 50 K. The thermal resistivity W at temperatures > 14 K is practically independent on deformation. At lower temperatures W is found to be proportional to AT−3 before and to AT−3 + BT−2 after deformation. A is due to boundary scattering, B due to dislocations.
Polymorphic transitions of ice at a pressure up to 2500 MPa in the temperature range 90–300 K
Authors: Sirota N. N. , Bizhighitov T. B.
Published: January 2007

In the present work the phase P—T diagram of ice is constructed in the temperature range 90–250 K and is ascertained at temperatures 250–300 K and pressures up to 2500 MPa. A new modification of ice — ice XII — was found. Compressibility and Grüneisen coefficients for a number of ice modifications were determined.
Infrared optical characterization of (Cu2GeSe3)1−x (CuGe2P3)x mixed crystals
Authors: Riede V. , Sharif N. , Neumann H. , Omar M. S. , Sobotta H.
Published: January 2007

Infrared reflectivity spectra of (Cu2GeSe3)1−x(CuGe2P3)x mixed crystals with x = 0.1 and 0.2 are measured in the wave‐number range from 180 to 4000 cm−1. An analysis of the spectra reveals contributions from five vibrational modes and from free carriers to the reflectivity. The results are compared with previous measurements for Cu2GeSe3 and CuGe2P3.
Interference pattern of X‐ray waves inside the crystal and its image in vacuum in double‐field approximation (I)
Authors: Aslanian V. G. , Bezirganian H. P. , Bezirganian P. H.
Published: January 2007

The distribution of intensity of the interference field during simultaneous superposition of all the four Bloch waves in a two‐mode case has been investigated. It is shown that the distribution of intensity of the total field in the upper layers of the crystal is of a periodic character in two mutually‐perpendicular directions. In the lower layers, where the first field is absorbed, a sinusoidal distribution occurs only in the direction of the reciprocal lattice vector.
Energy bands of the BCC metals rubidium and cesium
Authors: Radwan A. M.
Published: January 2007

Energy bands of BCC rubidium and cesium are calculated for the first time using the full non‐local but energy‐independent Shaw's optimized model potential. The energy dependence of the potential is then included as first order perturbation. The effects of changing the model potential and of reversing the sign of the depletion charge d are reported. The Fermi energy EF is calculated in all cases. Our results are compared with those obtained by other authors. The band gap at N is very small for both metals, except when all model potential parameters are increased considerably (50% to 100%).
Freezing of aqueous solutions containing gases
Authors: Wojciechowski B. , Owczarek I. , Bednarz G.
Published: January 2007

The Mpemba effect and possible relation to the gases dissolved in water is investigated. The time of cooling and freezing of water and the enthalpy of its freezing in relation to the start temperature of cooling and the gases dissolved in water are measured.
Solidification behaviour of organic eutectics and 1:1 addition compound: p‐Phenylenediamine‐resorcinol system
Authors: Rai U. S. , Mandal K. D.
Published: January 2007

The phase diagram of p‐phenylenediamine‐resorcinol system, determined by thaw‐melt method, shows the formation of a 1:1 molecular compound and two eutectics. The linear velocity of crystallization, determined by measuring the rate of movement of growth front in a capillary, indicates that crystallization data obey Hillig‐Turnbull equation:

Where u and n are constants and ΔT is undercooling. X‐ray diffraction data of the molecular compound, eutectics and pure components infer that these eutectics are not simply the mechanical mixture of the two components and there is preferential ordering of atomic planes during their formation. The infrared studies carried out on this system reveal the intermolecular hydrogen bonding between two components forming the molecular compound. Using experimental values of heats of fusion, entropy of fusion and excess thermodynamic functions were also calculated.
Photoconductivity of rare‐earth‐doped (CdSe, ZnS)
Authors: Bhushan S. , Giriya L. C.
Published: January 2007

Photoconductivity rise and decay curves of (CdSe, ZnS) doped with La and Dy separately are investigated as a function of ambient temperature and pressure, electrode material and cell thickness. Using a number of metal electrodes Fe is found to give maximum IPC/IDC ratio for (CdSe, ZnS): La and Cu for (CdSe, ZnS): Dy. Due to change in temperature, maximum IDC and IPC are found to 70 °C. A possible mechanism is proposed for thermal and photo‐excitations in terms of these results. At lower ambient pressure the photocurrent is found to be low. Cell thickness effect also shows changes in IPC.
Chemical reactions during alkaline treatment of dealuminated Y zeolites — impossibility of aluminium reinsertion into the framework
Authors: Lutz W. , Lohse U. , Fahlke B.
Published: January 2007

During the alkaline treatment of dealuminated Y zeolites the non‐framework aluminium species and parts of the dealuminated SiO2‐rich framework are dissolved in the alkaline medium. After reaching certain concentrations of silicate and aluminate anions in the solution an aluminium‐rich gel (Si/Al = 1.7) precipitates. The aluminosilicate gel is well‐ordered in short ranges and gives rise to discrete peaks in the 29Si MAS NMR spectrum.

No evidence for aluminium reinsertion into the zeolite Y framework was obtained.
Diamagnetism and some peculiarities of interatomic interactions in Cu2Sb
Authors: Vitkina Ts. Z. , Zhigadlo N. D. , Ryzhkovskii V. M.
Published: January 2007

Results are reported for magnetic susceptibility measurements of high purity Cu2Sb which characterize it as a diamagnetic. The observed anomalies of magnetic susceptibility, electrical resistivity and linear expansion coefficient in the neighbourhood of 370 K verify the existence of a phase transition of nonmagnetic origin in this temperature range. The analysis of the peculiarities of interatomic interaction in Cu2Sb indicates the covalent character of the bonding. The value of the strength of the CuCu and CuSb bond is evaluated. It is shown that the CuCu bond in the Cu2Sb compound is the most strong one.
Microcomputer programming of dosage rate during batch precipitation
Authors: Jones A. G. , Teodossiev N. M.
Published: January 2007

Application of a microcomputer control system to programme the dosage rate during a batch precipitation is described. The technique is tested with the drowning‐out precipitation of potassium sulphate from aqueous solution using acetone. Programmed dosage controls the transient supersaturation and crystal growth rate thereby improving the product crystal size distribution. A consequent improvement in filtrability characteristics is also indicated.
On the structure of thin plasma‐treated thermal SiO2 films
Authors: Popova L. I. , Atanassova E. D. , Peneva S. K. , Tcukeva E. A.
Published: January 2007

Oxygen‐plasma‐treated thin thermal SiO2 films (15–100 nm) have been studied by Reflection High Energy Electron Diffraction (RHEED). The presence of unconventional type microcrystalline regions (not only tetrahedrally coordinated) in the amorphous matrix of the oxides is established. Thinner oxides (15–50 nm) are more sensitive to the plasma action. In general, oxygen plasma leads to an additional deformation and decomposition of the initial crystalline forms and causes a degradation of the electrical parameters of the samples.
Magnetic and electric properties of the ternary alloys AB
Authors: Vitkina Ts. Z. , Smolyarenko E. M. , Trukhan V. M.
Published: January 2007

The results of experimental studies of the electrophysical and magnetic properties of solid solutions based on the AB compounds with anion (Zn3(PxAs1−x)2 and cation (ZnxCd1−x)3 P2 substitution are reported. The Zn3(AsxP1−x)2 solid solutions are characterized by p‐type conductivity (∼ 1015  1017 cm−3), low Hall mobility and conductivity of ∼ 10−2 — 10−3 ohm−1 cm−1. In the (ZnxCd1−x)3P2 solid solutions the samples rich in zinc are p‐type, those rich in cadmium — n‐type, the carrier concentration is ∼ 1016 — 1018 cm−3. From the measurements of the magnetic properties of the above mentioned alloys it is shown that in the investigated solid solutions a transition from the structure with direct optical transition to those with indirect optical transition occurs.
Temperature variation of the phonon frequencies in V3Si along the [110] direction by the X‐ray inelastic scattering
Authors: Sirota N. N. , Poluchankina L. P. , Orlova N. S.
Published: January 2007

The investigation of the intensity of X‐ray diffuse scattering by the lattice vibrations along the second‐order symmetry axis in V3Si single crystals is performed at different temperatures from 300 to 8 K and the phonon dispersion curves in this direction are determined. It is found that the phonon frequencies of all modes decrease with lowering temperature.
On the morphological instability of the growing crystals (III). Micro‐interferometric investigations of the morphological stability of KDP crystals growing from aqueous solutions
Authors: Staynova M. , Nanev Chr.
Published: January 2007

The paper is aimed at the elucidation of the limits to which the faceted forms of KDP crystals preserve their stability and beyond which a skeletal growth from stagnant solutions takes place. In order to avoid the natural convections the experiments were performed in two‐dimensional cells. On the basis of quantitative criteria, it has been shown that the kinetic regime of growth has been replaced by a diffusion one when the concentration on the crystal surface drops with respect to the bulk value with 0.1% to 0.2%. The critical size above which the KDP crystal no longer retains its polyhedral growth mode in a diffusion regime since a gross morphological defect in the form of a depression appears on its (010) face has been compared with the theoretical expressions derived by Cahn and Chernov.
Anisotropic plasma etching of P‐doped poly‐Si with CCl4/He
Authors: Handke R. , Krzikalla R. , Lippert Gud.
Published: January 2007

An anisotropic and very selective etch process for high P‐doped polycrystalline Si has been developed using statistical methods for experimental design and analysis. Mixtures of CCl4 and He served as etching gas system. It is shown that only a low number of trials is needed to get good information about the process. One example is presented for the generation of a regression polynom and a computer graphic.
Beilby layers on crystal surfaces
Authors: Vlasov A. D. , Rez J. S. , Fil'chenkov M. L.
Published: January 2007

A concise review of Beilby's amorphous surface layers, discovered in early years of the twentieth century, is presented. While being treated mechanically the crystals form these layers characterized by an enhanced hardness and specific optical, electrical, and magnetic properties. The temperature stresses arising from a periodic contact of the abrasive with the crystal surface are supposed to be a reason for Beilby layer formation. A mathematical description of propagation of the temperature waves is given. The temperature wave amplitude is shown to be e times attenuated at the distance from the crystal surface being about the grain size.
Discontinuous dielectric reorientation in the SI phase of 4‐n‐Nonyl‐4′‐n‐nonyloxy‐azobenzene
Authors: Pelzl G. , Schiller P. , Demus D.
Published: January 2007

Planar oriented samples with positive dielectric anisotropy were used to study the dielectric reorientation in SI phases. It was found that the dielectric reorientation is characterized by the rotation of the molecule director around the layer normal. The field‐induced deformations do not arise simultaneously in the whole sample but they start in certain regions and grow continuously by domain wall motion. Depending on the boundary conditions three types of field‐induced deformations can be observed at different thresholds. An attempt has been made to interprete this behaviour on the basis of a simple model.
A synchrotron X‐ray diffraction study on structural changes of polycrystalline calcium hydroxyapatite during acid dissolution — methodic aspects
Authors: Pritzkow W. , Rentsch H. , Grosshans W. A. , Wroblewski T.
Published: January 2007

A procedure has been developed for following structural changes of pure synthetic calcium hydroxyapatite during its demineralization in a hydroxyethylcellulose solution. The procedure consists of demineralization and simultaneous powder diffraction patterns recorded with synchrotron X‐ray radiation. Experimental details will be described.
Crystal structures of two quenched CuInSe phases
Authors: Hönle W. , Kühn G. , Boehnke U.‐C.
Published: January 2007

The crystal structures of the δ‐phase with a composition of Cu0.46In1.18Se2.00 and of a Cu‐poor β‐phase with a composition of Cu0.39In1.20Se2.00, both quenched from 750 °C, have been determined with single crystals. The δ‐phase crystallizes with a = 576.2(4) pm in the ZnS‐type structure (space group F43m), the β‐phase with a = 575.5(3) pm, c = 1152.0(4) pm and Z = 4 in a new structure type for tetrahedral structures with the space group P42c. In both compounds the cations are statistically distributed together with vacancies. The number of vacancies is estimated from the crystal structure analyses and results to be (Cu0.54(2)In1.15(2)□0.30(2)) Se2 for the δ‐phase and (Cu0.36In1.09□0.55) (Se1.80□0.20) for the Cu‐poor β‐phase.
Experience with the diffusion‐grown surface layer on calomel single crystals (Hg2Cl2) exhibiting a higher refractive index
Authors: Barta Č. , Barta Č. , Gilar O. , Pavlíček Z. , Brožek V. , Hájek B.
Published: January 2007

The article deals with experience obtained in production of surface layers on calomel single crystals (Hg2Cl2), exhibiting higher refractive indexes, using the gaseous diffusion over the crystalline Hg2Br2. The values of the diffusion coefficient at three various temperatures (312, 352.5, 367.5 °C) were determined together with its approximate temperature dependence. This dependence was specified by finding characteristical values of the frequency factor (D0 = 7.1024 cm2 s−1) as well as the activation energy of the diffusion process (Q = 421.5 kJ · mol−1). Rise of equilibrium concentration of Br has been observed on the sample surface which corresponds to the production of a compound of composition 3 Hg2Cl2 · 2 Hg2Br2. Four different diffusion layers were produced showing a refractive index enhanced by 1.6 to 6.3% at the maximum in the depths of 14 to 342 μm. The investigated process renders possible to produce a light guiding surface layer on the calomel single crystals.
Photoconductivity decay and calculation of lifetime in ZnTe
Authors: Nagabhooshanam M.
Published: January 2007

Isothermal photoconductive decay in p‐ZnTe was used to determine the energy levels associated with the native defect acceptors as 0.024, 0.017, and 0.011 eV. The capture cross‐section and carrier lifetime were computed at different temperatures (77–200 K) by conjuncting these results with some theoretical equations. The results were explained on the basis of Zn vacancies and vacancy complexes.
Paramagnetic centers in X‐irradiated KH2PO4 crystals doped with chromium
Authors: Alybakov A. A. , Abdrazakov A. A. , Arbotoev O. M. , Kudabaev K.
Published: January 2007

EPR spectra of X‐irradiated KDP: CrO single crystals are studied both at room and liquid nitrogen temperatures. It is found that X‐irradiation of doped KH2PO4 (KDP) crystals at 77 K creates uncharged H2PO4 radicals parallel with HPO−4 ion‐radicals. It is shown that a part of the impurity chromium ions enters the crystal lattice in the trivalent state. As a result, paramagnetic centers with Cr5+ ions of a different origin are formed by X‐irradiation in KDP: CrO: Cr5+ of an electronic nature (appearing in the reaction CrO + e− → CrO) and Cr5+ of a hole nature (resulting from a successive capture of two holes by Cr3+ ions). Thermal stabilities of these paramagnetic centers are found to be different. Principal g‐values are determined for all investigated centers.
Influence of the quenched‐in state on the decomposition kinetics of Al‐21 at.% ZnX at.% Mn Alloys
Authors: Wendrock G. , Major B. , Löffler H. , Ciach R. , Król J.
Published: January 2007

The structure changes proceeding in a series of Al‐21 at.% Zn‐X at.% Mn alloys (X = 0, 0.13, 0.32, 0.6, and 2.0) were investigated during ageing at 80 °C by X‐ray (diffraction line analysis as well as small‐angle scattering) and TEM examinations. The main results are the following. (i) Mn additions of 0.6 at.% rise the boundary of the one phase region (TPB) for about 50 K. (ii) Mn additions accelerate the lamellar mode of decomposition, the mean size of the GP zones, however, is profoundly diminished. (iii) If quenching the specimens from Tq = Trhn + 15 K < TPB (Trhn is the upper limit temperature of the onset of rapid homogeneous nucleation of Guinier‐Preston (GP) zones) instead from Tq = 470 °C > TPB, the lamellar mode of decomposition is significantly accelerated, but the mean size of the GP zones growing between the lamellas is diminished.
Crystal structure of marmesin, C14H14O4, 2‐(β‐hydroxyisopropyl)‐2,3‐dihydro‐6,7‐furano‐coumarin
Authors: El‐Kordy M. , Farag I. S. Ahmed , Will G.
Published: January 2007

The unit cell parameters of this compound were determined by least‐squares calculations from the adjusted angular setting of 25 general reflections. The crystals are monoclinic with the following crystallographic data: a = 5.718(1), b = 13.794(4), c = 7.861(1) Å, β = 100.53(2)°, Z = 2 and Dx = 1.34 g · cm−3. The space group according to the systematic absences is P21.

The structure of this compound was solved by direct methods and refined by full matrix least‐squares with anisotropic temperature factors to R = 0.04. The refined atomic positions indicate a considerable strain within the molecule. The structure is built up from molecules connected by H‐atoms forming infinite chains along b‐axis.
Optical absorption spectra of epitaxial layer ‐ gradient layer ‐ substrate systems
Authors: Neumann H.
Published: January 2007

Theoretical relations are derived for the photon energy dependence of the absorption coefficient of epitaxial layer — gradient layer — substrate systems assuming a spatially linear variation of the gap energy in the gradient layer. It is shown that optical absorption measurements on such systems can be used to determine the gap energy of the epitaxial layer. Numerical calculations for the system GaAs0.3P0.7—GaAs1—xPx—GaP are presented.
Organometallic vapour phase epitaxy of galliumarsenide using Ga(CH3)3 · N(CH3)3‐adduct as precursor
Authors: Seifert W. , Ploska K. , Schwetlick S. , Butter E.
Published: January 2007

Epitaxial layers of GaAs have been grown by MOVPE using trimethylgallium‐trimethylamin‐adduct (TMGa‐TMN) as the Ga‐precursor. In comparison to the growth system using pure TMGa no significant influence on growth conditions and materials parameters could be found. The deposited GaAs is of fairly high quality with room temperature mobilities of 6700 cm2/Vs at free electron concentrations of about 1 × 1015 cm−3. No hints to nitrogen incorporation could be found.
Structure and properties of Na‐magadiite dependent on temperature
Authors: Brandt Astrid , Schwieger Wilhelm , Bergk Karl‐Heinz , Grabner Paul , Porsch Martin
Published: January 2007

The mechanism of the thermal behaviour of Na‐magadiite at a temperature range from 293–573 K was developed based on X‐ray diffraction, DTA, DTL, Q‐TG, and gravimetric measurements. A structure model (BRANDT et al.) previously proposed was additionally used.

It is possible to show that there probably is a connection between the typical modifications of basal spacing and significant shiftings of silicate sheets. Different steps of dehydration, decrystallization and structure variations can be ascribed to the several thermal transitions. The results depend on sample treatment such as the existent or not existent solid‐water vapour interaction and the establishment of equilibrium. It seems that there is a predominance of the first mentioned influence.
The development of a nematic two frequency addressing mixture
Authors: Stettin H. , Kresse H. , Schäfer W.
Published: January 2007

An example is given for the development of a nematic two frequency addressing mixture based on the equations for the threshold voltages, the switching times, and the dielectric relaxation. New substances have been synthesized with relaxation frequencies in the kHz range and big values of the static dielectric anisotropy at room temperature. The isotropy frequency and the relation between the high and low frequency dielectric anisotropy, respectively, are adjustable by adding of substances without a relaxation mechanism in the kHz range and with a big negative static dielectric anisotropy. The produced mixture was dielectrically investigated. Calculated and experimentally found data are in a good agreement.
The coloration effect in KCl: Eu2+ crystals γ‐irradiated at 200 K
Authors: Opyrchal H. , Macalik B. , Nierzewski K. D.
Published: January 2007

The formation of colour centers at 200 K in γ‐irradiated KCl crystals doped with Eu2+ ions in a wide concentration range is studied by optical absorption, EPR, and ITC method. The EPR and ITC measurements reveal the drastic decrease of concentration of isolated europium dipoles induced by irradiation at 200 K. Moreover, no correlation between concentration changes of colour centers and Eu2+ dipoles induced by irradiation and postirradiated annealing has been found. The results obtained are explained by radiation stimulated aggregation of Eu2+ dipoles into small clusters at 200 K.
Preparation of some lanthanide violurate complexes
Authors: Farag I. S. Ahmed , Awadallah R. M. , Gad A. A. M.
Published: January 2007

Violurate complexes of Ce3+, Pr3+, Pr4+, Nd3+, Sm3+, Eu3+, Gd3+, Dy3+, Ho3+, Er3+, and Yb3+ were prepared. The prepared complexes are freely soluble in hot water and dilute mineral acids. Thermal analysis (DTA, DTG, and TGA) show that the solid complexes are characterized by endo‐ and exothermic bands, indicating that they are degradated at different temperature stages. The IR spectra of the ligand and its metal complexes reveal that bonding takes place through coordination bonds between the central metal ion and the oxygen atom of the oximino (C = NO) group and the oxygen of the phenolic (ketonic group . All the isomorphous complexes, detected by the X‐ray diffraction patterns, have similar IR spectra.
Liquid phase epitaxial growth of undoped gallium arsenide from bismuth and gallium melts
Authors: Yakusheva N. A. , Zhuravlev K. S. , Chikichev S. I. , Shegaj O. A.
Published: January 2007

Electrical properties of undoped GaAs layers grown from Ga and Bi melts under identical conditions are compared as a function of growth temperature and pregrowth baking time. Identification of residual shallow donors and acceptors is performed by means of laser photoelectrical magnetic spectroscopy and low temperature photoluminescence. It is shown that a change of solvent metal results in complete alteration of major background impurities in grown epilayers due, mainly, to changes of distribution coefficients of these impurities. High purity, low compensation n‐GaAs layers can be grown from Bi melt (epilayers with the Hall mobility of electrons μ77K ≈ 150000 cm2/V · sat n = 2.5 · 1014 cm−3 has been grown).
Crystallization kinetics and the rule of Brönsted
Authors: Treivus E. B.
Published: January 2007

Logarithm constant of crystal growth rate for some Tutton's salts correlates with logarithm constant of equilibrium for this salts in solution that agrees with the rule of Brönsted.
Crystal growth and dislocation structure of gallium antimonide
Authors: Moravec F. , Šestáková V. , Štěpánek B. , Charvát V.
Published: January 2007

Single crystals of GaSb have been grown by the Czochralski method under reducing conditions. Crystals were grown in the 〈100〉, 〈111〉, and 〈112〉 directions. The 〈111〉 growth direction was found to be the most suitable for the successful and reliable crystal growth. Dislocation densities in 〈111〉 oriented crystals were examined by chemical etching. The etch pits density in these crystals didn't exceed the value of 1 × 102 cm−2.
On the preparation and electrical properties of thallium selenide monocrystals
Authors: Hussein S. A. , Nagat A. T.
Published: January 2007

Thallium Selenide single crystals were prepared by a special design using Bridgmantechnique constructed by the authors. An investigation was made on the influence of temperature on the electrical conductivity and Hall effect in two crystallographic directions. The anisotropic properties were checked, and the anisotropic factor was observed to increase with temperature decrease. The energy gap as well as the ionization energy was calculated. The conductivity throughout the entire temperature range was found to be of p‐type. The Hall mobilities derived from these measurements at room temperature were of the order μH⟂ = 42.66 cm2/vs and μH∥ = 112.2 cm2/vs.
Force constant scaling and interatomic potential in tetrahedral semiconductors
Authors: Neumann H.
Published: January 2007

The force constants of tetrahedral semiconductors derived from lattice vibration data are analysed in terms of a generalized Morse potential and of a potential with power laws of the interatomic distance for the repulsive and attractive term. It is found that the Morse potential is an appropriate model for describing the dependence of the force constants on the bond length in the elemental, AIIIBV, AIIBVI and AIBIIIC semiconductors.
InGaAsP quaternary layers on InP (100) substrate analysed by ion backscattering and channeling
Authors: Flagmeyer R. , Gottschalch V.
Published: January 2007

In1−xGaxAsyP1−y layers LPE grown on InP(001) substrates are analysed by the Rutherford backscattering and channeling techniques. In addition to the layer thicknesses the compositions are determined from the random spectra and compared with the PL and XRD results.

The high dechanneling rate of the He+ ions for [100] incidence is attributed to the displaced atoms in the distorted crystal lattice of these otherwise high‐quality epitaxial layers. We find a characteristic value of Δχdist(0.1) = 2.3 ± 0.3% which must be taken into account for estimations of crystalline quality.
Isomorphic substitutions in the CeO2La2O3 system at 850° C
Authors: Minkova N. , Aslanian S.
Published: January 2007

It was proved that there are two isomorphic series of mixed crystals in the CeO2La2O3 systems from 0 to 14 mol% CeO2‐mixed crystals based on the La2O3 structure and from 32 to 100 mol% CeO2‐mixed crystals based on the CeO2 structure. The oxides were obtained by co‐precipitation of oxalates, followed by heating at 850 °C. The changes of the parameters of the lattice with the changes of the composition were investigated. Also the solubility of the mixed crystals in 25% HCl was determined.
Vapour transport of CdCr2S4 and HgCr2Se4: Chemical equilibrium and crystal growth
Authors: Belyaev V. K. , Nikiforov K. G. , Radautsan S. I. , Bazakutsa V. A.
Published: January 2007

Theoretical and experimental studies of the CdCr2S4(HgCr2Se4): CrCl3 systems have been performed for the crystal composition control in the chemical transport growth. The balance partial pressures of the components have been calculated in a wide temperature range. It is shown that the CdCr2S4 composition control can take place with the powerful change of the transport agent quantity. Such control for the HgCr2Se4: CrCl3 system is more difficult. The calculated vapour phase composition is in good agreement with the determined one based on the measurements of the sound speed and transport rate.
Comparative infrared lattice vibration study of LiGaO2 and LiInO2 (I) experimental results
Authors: Sobotta H. , Kühn G. , Neumann H. , Riede V.
Published: January 2007

Infrared reflectivity spectra of LiGaO2 and LiInO2 samples pressed from powdered material are measured at room temperature in the wavenumber range from 180 to 4000 cm−1. The optical mode frequencies found for LiGaO2 agree with measurements on single crystals. In LiInO2 four vibrational modes are found. Comparing the results for LiGaO2 some conclusions are made with regard to the LiO bond related vibrational modes.