bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of etching conditions on surface contamination during silicon etching in CF4 plasma
Authors: Glück B.
Published: January 2007

The dependence of blanked‐etched silicon surface quality on the etch parameters and mask material was studied.

First it was tried to find such etch conditions, where the silicon surface keeps clean. It was found that etching in RIE‐mode yields better surfaces than in PE‐mode. There was no noticeable influence by variation the oxygen content in the CF4/O2‐etch gas mixture and the total gas flow. If the generator current was raised, the edge zone of the wafer, where the surface is contaminated, becomes greater.

Second it is shown that the presence of aluminium as mask material makes worse the surface quality. This effect is stronger during etching in the RIE‐mode than in the PE‐mode.
Optical absorption and photoelectric properties of Ga2In4S9 single crystals
Authors: Moldovyan N. A. , Chebotaru V. Z.
Published: January 2007

Presented in this paper are the results obtained from the investigation of absorption edge and photoconductivity of layered Ga2In4S9 single crystals as well as from the investigation of the photovoltaic effect in Pt—Ga2In4S9 surface‐barrier structures. We determined the magnitude of the direct band gap to be Eg = 2.72 eV and the position of the sensitizing centres to be ≈︁0.15 eV above the valence band top. In the regions of the photon energies smaller than Eg the absorption band edge is described by an exponential dependence with a temperature independent slope.
Growth of CdBr2 crystals by zone‐melting and study of their growth features
Authors: Shukla Nutan , Trigunayat G. C.
Published: January 2007

A detailed surface microtopographic study has been carried out on the (0001) faces of melt‐grown CdBr2 single crystals. Mainly the growth of the crystals takes place by continuous solidification at the solid‐liquid interface. Rarely, the growth occurs by two‐dimensional nucleation and still more rarely by spiral mechanism. Most spirals are seen to be polygonized such that the polygonization extends right upto the centres of the spirals.
Purification, growth and ESR studies of sodium nitrate
Authors: Phor J. S. , Chaudhary S. K. , Maken S.
Published: January 2007

Single crystals of sodium nitrate have been purified and grown using zone‐refining system fabricated in our laboratory. Laue photographs were employed to check the crystallinity. X‐ray irradiated crystals have been studied by electron spin resonance.
Crystallization of glaserite from aqueous solutions
Authors: Mazzarotta B.
Published: January 2007

Crystallization of glaserite (double salt of potassium and sodium sulphate) from aqueous solutions was studied by determining solubility, metastable zone width, growth and dissolution kinetics. Solubility measurements confirmed the presence of a large range of mother liquor compositions from which the precipitation of glaserite at about 73 – 76 wt% K2SO4 is obtained: inside this region the solubility lines resulted curvilinear. The metastability zone is quite large, ranging from 14 to 23 °C, and mainly increases by increasing the Na2SO4 content in the mother liquor. The growth rate of glaserite is second order, slightly size dependent and primarily controlled by diffusion as for K2SO4 but both growth and dissolution constants are quite lower than those for K2SO4.
Stabilizing effect of non‐framework AL on the structure of dealuminated y zeolites under hydrothermal conditions
Authors: Lutz W.
Published: January 2007

With the dealumination of Y‐type zeolites a modification of catalytic properties as well as a ultrastabilization is attained. With increasing Si/Al ratio the hydrothermal stability should decrease. However, the non‐framework aluminium, containing as amorphous aluminosilicate protects the modified framework against the attack of water.
The influence of different acceptor coactivators on the luminescent properties of CaS: Ce polycrystals
Authors: Bushtruk I. Ya. , Demishev S. V. , Gruzintsev A. N.
Published: January 2007

The influence of coactivators, namely, alkali metals, on the luminance, spectral characteristics and defect composition (by thermoluminescence curves) of green luminophor CaS:Ce obtained by solid phase synthesis, is considered. The use of sodium and potassium is shown to increase the efficiency of cathode luminiscence from 8.5% to 20% and 15%, respectively. This is due to the effect of self‐compensation of the activator (Ce) and coactivator impurities changing the amount of calcium sulfate intrinsic defects. Studies have been made of the thin structure of the luminophor spectrum at 4 K.
The d‐d transition spectrum and Cu(II)‐N bonds of [Cu(2,2′‐bipyridine)2 (saccharin)] (saccharin) · 3 H2O
Authors: Jianmin Li , Yugeng Zhang , Jifa Fan
Published: January 2007

Following a recent upsurge of interest in saccharin complexes system, we have synthesized several saccharin mixed ligand complexes and attempt to discussed them. In this work, the d‐d transition spectrum of the title compound crystal have been determined and it is explained with scaling radial theory of non‐free ions which was proposed by our laboratory. However, the absorption position of d‐d transitions of the title compound are at 10474, 12435, 13814, 15627 cm−1. With data in the work of Brown and Shannon, Cu(II)‐N bonds of the title compound are discussed and it shows that the coordination ability of saccharin in to copper(II) ion is weaker than that of 2,2′‐bipyridine, but more stronger than that of a water molecule.
On the morphological stability of cubic symmetry class crystals (KBr) growing from aqueous solutions
Authors: Staynova M. I. , Nanev ChR. N.
Published: January 2007

Morphological stability is a complex problem, the clarification of which requires the simultaneous consideration of the natural transport of matter by diffusion and the surface incorporation kinetics, hence the distribution of concentration around the growing crystal (Seeger; Cahn; Chernov). In the present paper the instability of KBr single crystals due to the appearance of depressions on their faces during growth from aqueous solutions has been related with the actual concentration distribution on their surfaces and the directly measured growth rates.
Nucleation velocity of NaPO3 melts
Authors: Grantscharova E. , Gutzow I.
Published: January 2007

The time τ for visible crystallization of NaPO3 melts is measured in the whole range of undercoolings from the melting temperature Tm to the temperature of vitrification Tg. It is shown that the time τ, needed for the appearance of a visible crystallization at high supersaturations is determined by the linear growth rate, whereas the rate of heterogeneous nucleation is the main factor, determining the experimentally measured time τ at low supersaturations. The specific surface energy σ at the melt‐crystal interface is calculated from the data on nucleation velocity in the vicinity of Tm and the temperature dependences of both heterogeneous and homogeneous nucleation velocity for NaPO3 melts are constructed. It is concluded that at normal cooling rates only nucleation, initiated by active crystallized cores could be observed for NaPO3.
Growth and characteristics of HgGaInS4 single crystals
Authors: Moldovyan N. A. , Chebotaru V. Z.
Published: January 2007

Single crystals of the HgGaInS4 layered compound were grown by the iodine transport technique. Results of their optical, photoelectric, and radiative properties' study are presented. The band gap and the binding energy of holes on the sensitizing centres were determined to be Eg = 2.41 eV and Ea = 0.2 eV, respectively. A presence of quasi‐continuously distributed states was stated which are responsible for the exponential segment of the absorption edge and which take part in the radiative recombination.
On the preparation and sintering behaviour of barium titanate
Authors: Pfaff G. , Feltz A.
Published: January 2007

The present contribution reports on the preparation of BaTiO3 powders in various ways including the characterization and the sintering behaviour. The powders were synthesized by using precursors like BaTiO(C2O4)2 · 4 H2O and BaTiO2(O2) · 3 H2O, or by an alcoholate/hydroxide method, by a successive precipitation from solutions with following thermal treatment, or by the conventional route from BaCO3 and TiO2. The thermal decomposition of the precursors to BaTiO3 is described. The different sintering behaviour of BaTiO3 compacts is the consequence of granulometric properties and of their content of impurities. Possible sintering mechanisms are discussed.
On the thermal behaviour of molecular beam effusion sources
Authors: Müller B. , Wolf B. , Zehe A.
Published: January 2007

Molecular beam epitaxy (MBE) takes advantage of crucibles indirectly heated by an electric resistance heater. These thermal sources can be used to evaporate a great variety of materials. A precise control of the evaporation rate, however, requires a temperature stability of about 1‰. Therefore, a detailed knowledge on the thermal behaviour of the source is indispensible.

It is intended to present models describing the response of the source temperature to a step change in heating power and compare the results by experimental data.
Microstructure optical and electrical studies of cadmium selenide thin films
Authors: Mahmoud S. , Eid A. H.
Published: January 2007

Nucleation and growth of cadmium selenide thin films are of considerable interest because of their direct effect on the optical and electrical properties of this material. Vacuum‐deposited layers on amorphous and crystalline substrates showed a polycrystalline structure. The layers were deposited at a pressure of 10−4 Pa, with two deposition rates of 12 nm/s and 15 nm/s. The electrical resistivity and the optical absorption were studied for a group of layers on quartz substrate. As well the morphology and the microstructure were investigated by X‐ray and electron microscopy. Few activation energies were estimated from the optical absorbance and thermo‐resistance.
The planning growth rate method shortening the initial transient length
Authors: Haibo Xie , Wei Wang Qi
Published: January 2007

Based on the mass conservation law, the growth rate program for shortening the initial transient length of the Bridgman‐Stockbarger method is derived. A theoretical analysis shows that the crystal homogeneity can be largely raised without reducing the productivity by using this growth rate program.
Switching effect with memory in thallium sulfide single crystals
Authors: Nagat A. T. , Hussein S. A. , Gameel Y. H. , Gamal G. A.
Published: January 2007

Thallium monosulfide single crystals have been grown and thin platelet specimens were prepared. The switching characteristics of TIS were studied in detail. Switching effect with memory was observed and reported for the first time. The influence of different variables such as temperature, light illumination, and sample thickness on the switching behaviour is considered. The obtained results are discussed.
“Crystallization E.M.F.” Investigation in the lithium niobate pulling process from the melt
Authors: Aleksandrovskii A. L. , Shumov D. P.
Published: January 2007

E.M.F. in the lithium niobate crystal‐melt system as a function of pulling and rotation rates, crystal diameter and orientation was determined. Total E.M.F. is a sum of thermo‐E.M.F. and “crystallization E.M.F.” Δφ. The logarithmic approximation Δφ = Δφ0 In (1 + /v0), where v is a growth rate, Δφ0 = 3.9 mV, v0 = 1.9 mm/h is adequate. The Δφ magnitude is independent within the experimental error on the rotation rate and crystal orientation, whereas it is slightly increasing along with the diameter increase. Some existing models of electric phenomena accompanying crystal growth are discussed and a new model based on charge carrier injection into solid during growth is proposed.
Growth and characterisation of Na3Sb2F9 single crystals
Authors: Benet Charles J. , Sivakumar K. , Gnanam F. D.
Published: January 2007

Optically clear single crystals of Na3Sb2F9 have been grown from solution by slow evaporation technique at constant temperature. Crystals of sizes upto 30 × 8 × 8 mm have been grown in a period of three months. Vickers microhardness measurements have been carried out on these crystals. Attempts have also been made to understand the nature of the cracks developed around the microindentation. Single crystal X‐ray diffraction studies have been carried out and cell parameters are determined.
Crystal structure investigation of [Mn(3‐CH3C5H4N)2(N3)2(H2O)2]
Authors: Mautner F. A. , Goher M. A. S.
Published: January 2007

The crystal structure of the title compound has been determined by single crystal X‐ray diffraction methods. [Mn(3‐CH3C5H4N)2(N3)2(H2O)2] crystallizes in the space group P 1 with a = 7.444(2) Å, b = 7.691(2) Å, c = 8.926(3) Å, α = 99.82(3)°, β = 108.80(2)°, γ = 114.99(2)° and Z = 1. Least squares refinement gave a R value of Rw = 0.046 for 1414 observed reflections.

The manganese atom in the title complex is octahedrally coordinated by two oxygen atoms of the water molecules and four nitrogen atoms; two N‐atoms are the end atoms of azide groups and the other two nitrogen atoms belong to the 3‐methylpyridine molecules. The polyhedra are linked via hydrogen bonds between the water molecules and the azide groups.
The effect of local centers on conduction and luminescence of boron nitride
Authors: Galanov Yu. I. , Konusov F. V. , Lopatin V. V.
Published: January 2007

Energetic and kinetic characteristics of charge carrier trapping and recombination centres in graphite‐like boron nitride produced by gas‐phase deposition are discussed. Local levels in X‐ray excited PBN are studied using the method of thermally activated spectroscopy of luminescence and conduction, and their position in the band gap is determined from the temperature dependences of the diffusive current and depolarization current. Acceptor and donor level models for different PBN are developed. Their influence on conduction and on luminescence is determined. The scheme of hole‐electron transitions by luminescence is suggested. The carbon influence on the nature of the defects creating local levels is discussed.
Kinetics of growth of calcite crystals in presence of ammonium ions
Authors: Söhnel O. , Handlířová M. , Macenauer J.
Published: January 2007

The growth of calcite crystals from an aqueous supersaturated solution of initial concentration 0.15 mol m−3 containing 10 mol m−3 of (NH4)2CO3 has been studied at 298 K. The progress of growth has been followed through determining the composition of the solution by chemical analysis. The crystal growth is controlled by the surface reaction mechanism and satisfies a kinetic equation of the second order with the rate constant 3.7 × 10−6 m4 mol−1 s−1 that is independent on the surface area of the present solid. NH4+ ions do not change the crystal growth mechanism but decrease the growth rate of calcite crystals.
Growth of KDP crystals by splicing “parallel”‐seed in aqueous solution and its mechanism
Authors: Feng Pan , Jinkui Liang , Genbo Su , Qinglan Zhao , Youping He , Yisen Huang
Published: January 2007

Growth of the habit of a single seed and the special growth of splicing “parallel” seeds were investigated and compared with. Chemical etching and X‐ray topography were used to characterize spliced KDP crystals. The kinetic data in different growth stages were measured. It is concluded that secondary capping is the most important stage in the splicing parallel‐seed growth, and that the subgrain boundaries emitted from the secondary cap are parallel to or overlap with the splicing boundary and stretch to the prismatic surface about 45° to the z‐axis, and that above the twin‐crystal regions with subgrain boundaries the real monocrystalline region appears. The growth kinetics of the subgrain boundary approximately corresponds to the growth mechanism of single‐spiral dislocation.
Solidification behaviour of eutectic and monotectic alloys: Succinonitrile ‐ acenaphthene system
Authors: Rai U. S. , Shekhar H.
Published: January 2007

The phase diagram of succinonitrile‐acenaphthene system, determined by the thaw‐melt method, shows the formation of a eutectic at 0.99 mole fraction of succinonitrile and a monotectic at 0.35 mole fraction of succinonitrile with a large miscibility gap. The linear velocity of crystallization (v) of the pure components, eutectic and monotectic, studied at different undercooling (ΔT) by measuring the rate of movement of the growth front in a capillary, suggests that crystallization data obey the equation: v = u(ΔT)n where u and n are constants depending on the nature of solidification of the compounds. While the microstructural investigation of eutectic shows broken lamellar and eutectic dendrite‐type morphologies that of monotectic exhibits fibrous and broken fibrous‐type microstructures depending on the rate of solidification.
Dependence of electrical conductivity and activation energy of lithiumzinc ferrites on sintering temperature and porosity
Authors: Ravinder D. , Seshagiri Rao T. , Muley V. N. , Reddy K. B.
Published: January 2007

The electrical conductivity (σ) and thermoelectric power (Q) of polycrystalline lithiumzinc ferrites sintered at 1200 and 1300 °C was investigated as a function of temperature. The porosity and activation energy were calculated. It was found that the electrical conductivity is progressively increasing with increase of sintering temperature while the porosity and activation energy decrease continuously. The carrier concentration (n) and mobility (μ) of charge carriers has been discussed as a function of sintering temperature and temperature, respectively.
The goldstone mode of a liquid crystalline thiadiazole derivative
Authors: Kresse H. , Tschierske C. , Linström B. , Kremer F. , Vallerien S. U.
Published: January 2007

Dielectric measurements in the kHz‐range on (S)‐2‐(4‐n‐octyloxyphenyl)‐5‐[4‐(4‐methyl‐2‐chloropentanoyloxy)‐phenyl]‐1,3,4‐thiadiazole have been carried out in the smectic C* phase. A very intensive Goldstone mode (Δϵ = 3000, ƒR = 20–80 Hz) was found between 330 and 380 K. The expected unwinding of the helix with different dc bias fields could not be detected due to the increasing conductivity of the sample.
Growth and Characterization of Single Crystals of the Ternary Compound TlGaTe2
Authors: Nagat A. T. , Gamal G. A. , Hussein S. A.
Published: January 2007

The electrical conductivity and the Hall effect for TlGaTe2 crystals have been measured over a wide temperature range. The crystal used for our study was grown by the Bridgman technique and possessed p‐type conductivity. The energy gap has been found to be 0.84 eV, whereas the ionization energy has the value 0.25 eV. The variation of the Hall mobility as well as the carrier concentration with temperature was investigated. The scattering mechanism of the carrier in the whole temperature range of investigation was checked.
Calculation of Diffusion‐limited Growth of Hg1−x Cdx Te Epilayers on CdTe from Te‐rich Melts by Step‐Cooling LPE
Authors: Teubner T. , Winkler M. , Boeck T. , Parthier L.
Published: January 2007

Calculations of layer thicknesses and composition profiles in Hg1−xCdxTe layers on CdTe substrates for the growth from Te‐rich melts have been carried out for liquidus temperatures of 460 °C, 480 °C, and 500 °C. This has been made on the basis of the multicomponent diffusion model of SMALL and GHEZ and the solid‐liquid phase relation of BRICE. It could be shown that growth velocity increases only slightly with rising liquidus temperature. On the other hand, the interdiffusion velocity of Hg and Cd in the solid increases remarkably at a higher temperature. Therefore, to get layers with a constant x‐value a higher supersaturation of the melt is necessary. The x‐value decreases with rising supercooling by about 0.003 K−1. To demonstrate the thermodynamically and kinetically advantageous properties of CdTe as substrate material, comparative calculations for a “hypothetical” HgTe substrate have been involved.
The Detection of Salting‐out. A Comparative Study
Authors: Martin J. , Alcantara R. , Garcia‐Ruiz J. M.
Published: January 2007

We present a new device for the measurement of the metastable zone width and related parameters. The salting‐out is detected by using simultaneously seven different methods: a) visual detection, b) intensity of the transmitted laser beam, c) noise associated to (b), d) intensity of the reflected laser beam, e) noise associated to (d), f) conductivity, and g) pH. Full computerization permits an easy and quick take of data on the evolution of the nucleation and crystal growth processes. The use of this apparatus shows that the waiting time for the growth component of the induction time is minimized for the method using the noise associated to the reflected light as the recorded parameter. This comparative study shows that the maximum undercooling and maximum allowable supersaturation values obtained by the different tested methods present significant differences between each other. Meanwhile, we propose that the tabulated values of such parameters should specify the experimental way followed for the obtainment of reliable data.
Studies on F‐Band Absorption of Irradiated NaCl Single Crystals Excited with Laser Light
Authors: Prasad G. , Rao K. V.
Published: January 2007

The absorption in F‐band of NaCl single crystals after X‐ray irradiation and later excited with laser light is studied. Similar investigations have been carried out when these crystals are subjected to high AC electric fields prior to X‐ray irradiation and also at elevated temperatures. Effect of laser excitation on γ‐ray irradiated samples is studied. An attempt is made to understand the results in terms of the disorder that sets in in these crystals.
Effect of Electric Field on Dielectric Properties of SnO2 Sb2O3 and their Mixed Thin Films
Authors: Kumar J. Siva , Rao U. V. Subba , Rao K. V. Satyanarayana , Reddy K. Narasimha
Published: January 2007

Thin films of various thicknesses in the MIM structure have been prepared from the the powders of SnO2, Sb2O3 and (SnO2 + Sb2O3) of high purity by the thermal evaporation technique in a vacuum of 10−5 Torr. Dielectric properties of SnO2, Sb2O3, and their mixed thin films have been studied with ac and dc electric fields and frequency. Capacitance and loss tangent are almost independent on dc voltage upto 1.0 V for SnO2, 10.0 V for Sb2O3 and 2.5 V for mixed films. These capacitors become unstable at 1.0 V for SnO2 films and 2.5 V for mixed films. For higher film thicknesses the decay in these films starts at higher voltages. Capacitance and loss tangent increases with applied ac voltage in SnO2, Sb2O3, and their mixed films. A comparison of the capacitance values of SnO2, Sb2O3, and their mixed films showed that the capacitance values are less in Sb2O3 as compared to SnO2 films. In mixed films the capacitance is greater than the constituent films. These studies have shown that Sb2O3 films are found to be more stable compared to SnO2 and their mixed films for ac and dc voltages. The results thus obtained on SnO2, Sb2O3, and their films are presented and discussed.
An EPR Study of Scapolite
Authors: Vassilikou‐Dova A. B.
Published: January 2007

In single crystals of scapolite from two different localities, three paramagnetic centres are detected by electron paramagnetic resonance (EPR): 1. One isotropic singlet with giso = 2.005; 2. One triclinic singlet with g‖ = 2.005 ± 0.001 and g⟂= 2.009; 3. One triclinic sextet with g‖= 2.005 ± 0.001, g⟂ = 2.011; A‖ = 85.4 × 10−4 cm−4, A⟂ = 85.3 × 10−4 cm−1.

Centres 1 and 2 can be attributed to colour centres as they are bleached after annealing.

Centre 3 can be due to Mn2+ (only the central Ms = ± 1/2 transition is observable) most likely substituting for Ca2+ The site symmetry must be triclinic but due to Al, Si disorder and mixed Na, Ca composition the different components from magnetically non‐equivalent sites are averaged out for many orientations.
Surface Reconstruction of a Crystal Growing from a Partially Dissolved State: An In‐Situ Study
Authors: Prasad P. B. V.
Published: January 2007

In‐situ studies made on an urea‐palmitic acid adduct crystal, related to the sequence of growth: layeral growth – break down of layeral growth – 2D promoted growth, are presented.
On the Existence and Formation of Y4Al2O9
Authors: Papadopoulos Ilias
Published: January 2007

For the preparation and transformation sequence in the system Y4O3–Al2O3 the sintering of homogeneously mixed oxide powders was chosen. The constituents of the Y4Al2O9 phase were determined by quantitative phase analysis with the method of inner standards. Corresponding gauge curves for the conditions of the temperatures of sintering were drawn.

At low temperatures appears as first in the whole molar range the (2:1) phase, i.e. Y4Al2O9. With increasing temperature and sintering time the yield of this mixed crystal phase depends on the concentration of the oxide components in the powder mixture of the start materials.

In flux mixtures of the components PbO, PbF2, and B2O3 and despite suitable nucleation it was not possible to obtain this compound. In the melt the compound Y4Al2O9 was prepared frequently in near molar conditions. Also a glass was prepared with (2:1) stoichiometry. Single crystals were identified by X‐rays.
Dependence of Electrical Conductivity (σ) and Activation Energy of Lithium Ferrite on Sintering Temperature and Porosity
Authors: Ravinder D.
Published: January 2007

The electrical conductivity (σ) of lithium ferrite sintered at 950, 1000, 1050 and 1100 °C was investigated in the temperature range of 300 to 1000 K. Three distinct regions have been observed in log (σT) vs 103/T curves for four samples of lithium ferrite sintered at different temperatures. The conduction in the first region is due to impurities. In the second and third region is due to ordered and disordered state of the material. The transition from the first region to the second region is due to lowering of symmetry. The transition from second to third region is due to magnetic transition, i.e. ferrimagnetic to paramagnetic state. The transition temperatures are nearly equal to the Curie temperatures of the materials. The porosity and activation energy were calculated. It was found that the electrical conductivity is progressively increasing with increase of sintering temperature while the porosity and activation energy decrease continuously. The Seebeck coefficient (Q), carrier concentration (n) and mobility (μ) of charge carriers have been discussed as a function of sintering temperature and temperature.
A Study on the Microhardness of Organic Molecular Solids
Authors: Marwaha R. K. , Shah B. S.
Published: January 2007

An extensive study of the variation of microhardness with load in a large number of crystals of some organic molecular solids has been carried out. The plots of hardness versus load show peaks at specific loads and these have been attributed to the different slip systems in these crystals. These slip systems are in accordance with the crystal structure of these crystals and are dependent on the shape and way the molecules are geometrically deposed in the unit cell of the crystals.
On the Behaviour of Iodine in Indium Arsenide
Authors: Hitova L. , Trifonova E. P. , Sidorov A. F.
Published: January 2007

N‐type bulk samples of iodidely synthesized InAs prepared by rapid or orientated crystallization have been investigated with the laser mass‐spectrometer LAMMA‐1000 for qualitative and quantitative determination of iodine. Considerations on the position and electrical activity of iodine in the crystal lattice of InAs have been made. A clearly expressed dependence of the current carriers concentration on the iodine concentration has been established.

The obtained experimental data proved an earlier supposition that iodine acts as a donor impurity in the iodidely synthesized indium arsenide.
Mechanical Damping of YBa2Cu3O7 –x at Temperatures above 300 K
Authors: Klimm D. , Hofmann P. , Paufler P. , Reichelt W. , Körbl U.
Published: January 2007

Damping of ultrasonic waves with frequencies in the 100 kHz region was measured in the temperature region 300 … 1000 K. Two peaks could be observed (near 400 K or near 700 K, respectively). Occurrence of these peaks depends on oxygen content of the sample. The higher temperature peak is attributed to phase transition Pmmm 〈– – –〉 P 4/mmm of YBa2Cu3O7 – x.
IR‐device Grade (Hg, Cd)Te Crystals Grown by a Modified Bridgman Method
Authors: Bittner H. , Höschl P. , Schubert B.
Published: January 2007

Electrical and photoelectrical properties of IR‐devices manufactured on (Hg, Cd)Te‐wafers cut from single crystals grown by modified Bridgman method are reported and compared to those of devices made on THM‐(Hg, Cd)Te.

MIS‐structures and photodiodes were used in order to investigate the different materials.

The influence of material parameters and device technology respectively is involved in our discussion of device properties. The quality of modified Bridgman‐(Hg, Cd)Te was found to be comparable to that of the THM‐(Hg, Cd)Te.

AtT= 80 K and FOV = 60° background limited detectivity of photodiodes with a cut‐off wavelength of λco= 10.7 μm was achieved.
Transport Coefficient of Gallium‐doped Bi2Te3 Single Crystals
Authors: Navrátil J. , Lošťák P. , Horák J.
Published: January 2007

Gallium‐doped Bi2Te3 single crystals were prepared by means of a modified Bridgman method. Temperature dependences of the Hall constant RH(B ∥ c), electrical conductivity σ⊥c and Seebeck coefficient S(Δ T ⊥ c) were measured on the samples of these crystals in the temperature interval of 100–400 K. The variations of the investigated transport coefficients with increasing Ga content in the samples showed that Ga atoms in the Bi2Te3 crystal lattice behave as donors. This effect is qualitatively explained on the basis of a model of point defects in Bi2Te3(Ga) crystals; singly ionised gallium atoms in interstitial sites; Gai, are considered to be the most probable defects.
Saturation Behaviour of In – Ga – As Melts and Growth of In.53Ga.47As Lattice‐matched to (001) InP Substrates
Authors: Gottschalch V. , Knobloch G. , Butter E.
Published: January 2007

This paper presents the saturation behaviour of In – Ga – As melts with monocrystalline GaAs. The coulometric As‐analysis confirmed that the source‐seed‐technique produces In – Ga – As melts of defined compositions. The growth results of the step cooling technique applying both the source‐seed technique and the single phase melts are compared.
Infrared Lattice Vibrations in NaGaO2
Authors: Sobotta H. , Neumann H. , Schumann B. , Kühn G. , Riede V.
Published: January 2007

Infrared reflectivity spectra of NaGaO2 samples prepared from powdered material are measured at room temperature in the wavenumber range from 180 to 4000 cm−1. An analysis of the spectra with the Kramers‐Kronig method reveals 16 vibrational modes. From a comparison of the results for NaGaO2 with previous measurements on the isostructural compound LiGaO2 conclusions are made with regard to the Ga–O and Na–O bond related vibrational modes.
Mechanoluminescence in Centrosymmetric Crystals
Authors: Chandra B. P. , Tiwari S. , Ramrakhiani Meera , Ansari M. H.
Published: January 2007

The paper reports that the mechanoluminescence (ML) is not an inherent property of only the non‐centrosymmetric crystals. The ML may appear in number of centrosymmetric crystals due to variety of processes. The ML of 82 centrosymmetric crystals are reported and different models are proposed for the ML excitation. The models proposed are: space charge electrification model, triboelectrification model, phase transformation model, gas adsorption model, chemical reaction model, thermal population model, molecular deformation model, cleavage electrification model, defective piezoelectric phase model, dislocation defect stripping model, dislocation unpinning model, dislocation annihilation model, charged dislocation model and incandecent light emission model. It is shown that on the basis of the proposed model, intense mechanoluminescent materials with desired nature and characteristics may be prepared.
Influence of the Instantaneous Cooling Rate on Interface Shape during Temperature Gradient Technique (TGT)
Authors: Peicong Pan , Zhiying Lu , Fuxi Gan
Published: January 2007

Both analytical and numerical techniques show that the instantaneous cooling rate causes the interface to become increasingly concave in Temperature Gradient Technique. Dimensionless number De = R2QCpC0/[K (Th ‐ Tc)] is defined to express the extent in which the interface becomes more concave caused by the instantaneous cooling rate.
On the Bonding Types of V, Cr, …, Ga
Authors: Schubert K.
Published: January 2007

The electron correlations model allows to interpret the numerous structural phenomena in the elements V, …, Ga by merely two bonding types (FB2 and FB2). In Ge a third type (FB2C4) replaces the two types. The small number of bonding types suggests an improved approximation of the model to the observations.
Morphology and Microstructure of TiN and Ti(N, C) Thin Layers
Authors: Wokulski Z.
Published: January 2007

Thin layers of TiN and Ti(N, C) solid solution were obtained by the CVD process, making use of the following gas mixtures: TiCl4–N2–H2 for TiN and TiCl4–CCl4–N2–H2 for Ti(N, C). The thin layers deposition processes were carried out in the temperature range from 900–1450 °C. As growth substrates were used polycrystalline Al2O3, graphite, W, Mo and Cu plates and also single crystal Al2O3 (leucosapphire), (111) Cu and (111) Si plates. The influence of certain technological factors on the morphology of the layers obtained was studied. TEM examinations were also made of the microstructure of the thin TiN layers and the Ti(N, C) solid solution layers deposited on polycrystalline and single crystal Cu plates. Factors responsible for the presence of a high density of dislocations in the tested films were ascertained.
Crystal and Molecular Structure of 6α‐Methyl‐3,20‐Dioxo‐5β‐Pregnan‐17α‐yl Acetate
Authors: Scharfenberg‐Pfeiffer D. , Wenzel J. , Weiland J. , Bohl M.
Published: January 2007

The title compound 6α‐methyl‐3.20‐dioxo‐5β‐pregnan‐17α‐yl acetate crystallizes in the monoclinic space group P 21 with two molecules in the unit cell and the lattice parameters a = 10.889, b = 11.056, c = 9.8029 Å, β = 101.51° The crystal structure is isostructural with medroxyprogesterone acetate and refined by full matrix least squares calculations up to the discrepancy factor R = 0.051.
Dielectric Properties of Diphasic Composites of BaTiO3 and LiFe5O8
Authors: Sarah P. , Bhimasankaram T. , Kumar G. S. , Suryanarayana S.
Published: January 2007

A composite material has been prepared by sintering a mixture of a piezoelectric BaTiO3 and a piezomagnetic ferrite phase. The two‐phase nature of the composite has been characterised by X‐ray analysis. The electrical resistivity and dielectric properties of the composite material are studied as a function of the volume fraction of the components. The effect of poling on the dielectric constant is also discussed.
Determination of the Thickness of Chemically Removed Thin Layers on GaAs VPE Structures
Authors: Somogyi K. , Németh‐Sallay M. , Nemcsics Á.
Published: January 2007

Thinning of epitaxial GaAs layers was studied during the surface etching, with a special attention to submicron epitaxial structures, like MESFET or varactor‐type structures. Each chemical treatment influences the crystal surface during the device preparation processes, though the possible thinning of the active layer is small. Therefore a method allowing determination of thicknesses as small as at about 20 nm of the layer removed by chemical etching from GaAs VPE structures was applied. Using special multilayered structures and a continuous electrochemical carrier concentration depth profiling, the influence of the layer thickness inhomogeneity and of some measurement errors can be minimized. Some frequently used etchants and the influence of different – so called – non‐etching processes were compared in different combinations. It was shown that besides the direct etching a change of the surface conditions occurs, which influences the etch rate in the succeeding etching procedure.
Enhanced Growth of Nonpolar {001} Growth Sectors of Deuterated Triglycine Sulphate Doped with L‐Alanine (LADTGS)
Authors: Březina B. , Havránková M. , Váša M.
Published: January 2007

The crystals of deuterated triglycine sulphate substituted with L‐alanine (LADTGS) were grown from nonpolar {001} growth sectors by four different methods.

35 mol% of L‐alanine (LA) in the growth solution give a stable unipolarity of the crystals. A distribution of LA was measured by the electrical switching method using “hysteresis current” loops. A defect structure was observed in a microscope on the etched surface of crystals. Most uniform crystals have been obtained using an isothermal method without stirring of the growth solutions.
Crystallization of Calcium and Magnesium Phosphates from Solutions of Medium and Low Concentrations
Authors: Abbona F. , Franchini‐Angela M. , Boistelle R.
Published: January 2007

Calcium phosphates are precipitated at 25 °C from solutions of medium (Ca = P = 50 mM) and low (Ca = P = 10 mM) concentrations in the presence of magnesium. Experiments are also performed with solutions in which Ca + Mg = P = 50 mM and Ca + Mg = P = 10 mM. An amorphous calcium phosphate, Ca3 (PO4)2 · nH2O, and brushite, CaHPO4 · 2 H2O, are the phases first nucleated. The phases occurring one year later are brushite in the more concentrated solutions, hydroxyapatite (Ca5OH(PO4)3) and whitlockite (Ca9MgH(PO4)7) in the others. Octacalciumphosphate, Ca8H2 (PO4)6 · 5H2O, occurs as transitory phase. The effects of concentration, pH, supersaturation and magnesium on the precipitation and evolution of calcium phosphates, and the conditions for phase stability are discussed.
Study of the Deformation State of a Crystal Plate with Inclined Seed Boundaries
Authors: Lerche V. , Härtwig J.
Published: January 2007

The deformation state of crystal plates with an one‐dimensionally inhomogeneous concentration of point defects where the direction of inhomogeneity is arbitrarily inclined with respect to the surfaces of the plate was calculated according to the theory of elasticity for the general case of anisotropy. As an example synthetic quartz plates with seed boundaries were regarded. On the basis of the calculated strain field we simulated optical density distributions of X‐ray plane wave topographs of such crystals for a quantitative analysis of recorded topographs. Topography proved to be an alternative method in comparison with the determination of absolute lattice parameters for obtaining results concerning the anisotropy of quasiplastic strain due to the incorporation of point defects. Differing results on the basis of calculations according to the isotropic approximation of Hooke's law showed the necessity of anisotropic modelling in the present case.
Defect Engineering and Gettering in a High‐voltage Substrate Technolgy
Authors: Kissinger G. , Kissinger W. , Tittelbach‐Helmrich K. , Retzlaff U. , Knopke J. , Schmalz K. , Morgenstern G.
Published: January 2007

Defect engineering in the CZ‐silicon high‐voltage substrate technology with a polycrystalline support needs very deep denuded zones, which enclose the whole volume of the monocrystalline islands. The formation of crystal defects is compared in the substrate fabrication process with and without an outdiffusion annealing (15 h at 1250°C), respectively. The gettering efficiency of the polycrystalline support and of the buried layer at the island bottom has been studied. The influence of the defect density and the heavy metal contamination on the device parameters has been investigated at a high voltage p‐n‐p lateral transistor.
On the Chemical Mechanism of the Zinc Diffusion into GaAs from SiO2 Spin‐on Films
Authors: Nowak E. , Kühn G. , Schumann B. , Hesse R. , Sobotta H.
Published: January 2007

The chemical processes which take place during annealing were studied in both model substances and thin films deposited onto GaAs wafers by thermal analysis, X‐ray powder diffraction, IR spectroscopy, XPS and TEM. It was found that at 600°C only about 45% of the film was changed to SiO2 glass. At 700 °C begins the formation of zinc silicates. In this form the zinc seems to be scarcely able to diffuse into GaAs. Obviously, the exothermic DTA effect at 800 °C arises from this zinc silicate formation connected with a recrystallization of the amorphous film.
F.C.C. Rolling Texture Transitions in Relation to Constraint Relaxation
Authors: Wierzbanowski K. , Jura J. , Haije W. G. , Helmholdt R. B.
Published: January 2007

A complete set of f.c.c. rolling texture predictions, obtained with the use of a relaxed constraint model, is presented in this paper. The whole spectrum of textures between the copper and brass types can be found if some components of reaction stresses (between grains and the matrix) are relaxed. The best prediction of the copper type texture is found if ϵ13 is a free parameter and the other components of grain deformation tensor are controlled by reaction stresses. The best prediction of the brass type texture is obtained if ϵ12, ϵ13 and ϵ23 are free parameters. However, a decisive factor for the texture transition from the copper to the brass type is the relaxation of the ϵ12 component.

We present for all the considered cases the orientation distribution functions (O.D.F.) and also the pole figures for some selected cases.

Nous présentons pour tous les cas les fonctions de distribution d'orientations cristallines ainsi que dans certains cas — les figures de pǒles.
Satatistical Model of Mechanoluminescence in Crtstals
Authors: Chandra B. P. , Rahangdale Yuvaraj , Ramrakhiani Meera , Aansari M. H. , Sharma Y. K.
Published: January 2007

The present paper reports on a statistical model of the mechanoluminescence (ML) excitation in crystals where attempts have been made to explain stress, temperature‐, strain rate‐, activator concentration dependence and several other aspects of ML. It is found that ML emission should take place only during the period at which stress will change with time. The total ML intensity should be directly proportional to the square of the stress and there should be phase difference between the ML pulse and the applied stress pulse. It is found that the ML intensity should decrease faster with temperature as compared to the corresponding photoluminescence intensity. within the limit of concentration quenching the ML intensity should increase directly with the defect centre concentration. The ML intensity should increase with the stress rate or strain rate of the solids. Furthermore, the concept of mechanoluminescent and non‐mechanoluminescent materials is explored.
Single Crystal Growth and Electrical Properties of Gallium Monotelluride
Authors: Gamal G. A. , Nassary M. M. , Hussein S. A. , Nagat A. T.
Published: January 2007

Single crystals of GaTe were prepared in our laboratory by a special modified Bridgman technique method. Measurements of the electrical conductivity and Hall effect between 210 and 450 K were carried out on GaTe samples in two crystallographic directions. The Hall coefficient is positive and varies with the crystallographic direction. A unique mobility behaviour and strong anistropy in the carrier mobility were observed. The Hall mobilities parallel and perpendicular to the C‐axis, at room temperature, were 12 cm/V · s and 25.12 cm2/V ·s, respectively. The free carrier concentration lies between 1013 − 1014 cm−3 at room temperature.
Formation Volume of Vacancies in Elements and the Defect Formation Mechanism of Melting
Authors: Bollmann W.
Published: January 2007

The formation volumeVvof vacancies is given byVv= (hv/L) ΔVfwithhv= 8L(formation enthalpyhvof vacancies and heatLof fusion given in same units; ΔVf= change of volume due to melting). If there are phase transitions within the solid,Land ΔVfmust be replaced by (L+ ΔHt) and by (ΔVf+ ΔVt), respectively (ΔHtand ΔVtrefer to the heat (s) of transition (s) and to the volume change(s) due to transition(s), resp.). The pressure dependence of the melting point is dTm/dp= (TmVv)/hv. Independent of the sign ofVvany increase of the vacancy concentration above the maximum concentration possible within the solid decreases the melting point thus resulting in the observed surface melting. The melting point is fixed by the characteristics of vacancy formation (hv,Sv,Vv) and by the bulk modulus of the solid (Sv= formation entropy of vacancies).
Investigations on the Quasi‐binary System V2O5Ta2O5
Authors: Schadow H. , Oppermann H. , Wehner B.
Published: January 2007

By chemical transport reactions, in the system V2O5Ta2O5 another two compounds already described in literature were successfully isolated besides the two boundary phases. These are VTa9O25 and the compound VTaO5 occurring in two modifications. The transition point of the irreversible change of modification α‐VTaO5 → β‐VTaO5 was determined as 1153 ± 5 K in a quite good agreement with values cited in the literature.
Debye‐Waller Factors and Elastic Constants for Beryllium Oxide at Temperatures between 10 and 720 K (II). Elastic Constants from X‐ray Diffraction Data
Authors: Sirota N. N. , Kuzmina A. M. , Orlova N. S.
Published: January 2007

The method for determining the full elastic constants tensor for hexagonal crystals from the characteristic Debye temperatures obtained by X‐ray diffraction technique in different crystallorgraphic directions is given. All five elastic constants at different temperatures between 10 and 720 K for beryllium oxide with wurtzite structure are calculated using this method.
The Microhardness and the Toughness Anisotropy of Paratellurite Single Crystals in the Tr — 650 °C Temperature Range
Authors: Lomonov V. A. , Pisarevski Yu. V. , Sizova N. L. , Silvestrova I. M. , Dohnovskaya S. I. , Cholokov M. N.
Published: January 2007

The temperature hardness (Hv) and toughness (K1C) dependence of paratellurite (100), (010), (001) planes is investigated in the Tr −650 °C range. The correlation between the anisotropy degree of Young modulus and Hv is not found. The presence of 11 kind Hv and K1C anisotropy is shown.
Tribochemical Synthesis of Magnesium Zirconate for Some Specific Purposes
Authors: Gospodinov G. G. , Marchev V. M.
Published: January 2007

MgZrO3 was synthesized by tribochemical and thermal treating of a mixture of MgO and ZrO2 corresponding to its stoichiometry. The gained compound is identified by chemical and X‐ray analysis.
Rietveld Analysis of Mechanically Activated Powdered Zinc Ferrite
Authors: Šepelák V. , Tkáčová K. , Rykov A. I.
Published: January 2007

The mechanically induced changes in structure and magnetic properties of zinc ferrite were investigated by using the Rietveld analysis and Mössbauer spectroscopy. The formation of the spin arrangement in mechanically activated zinc ferrite is connected with a redistribution of the cations in the close‐packed anionic sublattice. On the basis of the Rietveld analysis the degree of mechanically induced inversion as well as the exact coordinates of atoms and lattice parameters in non‐activated and mechanically activated ZnFe2O4 was determined.
The Relation between Structure and Morphology of Magnetoplumbite‐type Crystal LaMgAl11O19
Authors: Jun Xu , Xiaoshan Ma , Xinmin Zhang , Yafang Shen , Guangzhao Wu
Published: January 2007

The magnetoplumbite crystal LMA is grown by the CZ technique. The orientations of all developing facets on the crystals are determined by means of X‐ray and optical methods, and Miller indices are calculated. According to the PBC theory, the relations between the morphology of LMA crystal and its structure are explained.
Phase Transition of Magnesium Sulphite Hydrates in Aqueous Suspension
Authors: Söhnel O. , Rieger A.
Published: January 2007

Solution mediated phase transitions in aqueous suspension (pH 9.5) of MgSO3 hydrates were studied at 50, 60, 65, and 70 °C for hexa‐ to trihydrate and 25, 30, and 35 °C for tri‐ to hexahydrate conversion. The former conversion is controlled by the diffusion growth of the new phase crystals whereas the latter process is controlled by both the initial phase dissolution and the new phase growth.