bluuebunny/crossref_metadata_2025_split huggingface dataset:
The goldstone mode of a liquid crystalline thiadiazole derivative
Authors: Kresse H. , Tschierske C. , Linström B. , Kremer F. , Vallerien S. U. 
Published: January 2007

AbstractDielectric 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

AbstractThe 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

AbstractCalculations 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

AbstractWe 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

AbstractThe 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

AbstractThin 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

AbstractIn 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.
On the Existence and Formation of Y4Al2O9
Authors: Papadopoulos Ilias 
Published: January 2007

AbstractFor 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

AbstractThe 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

AbstractAn 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

AbstractN‐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

AbstractDamping 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

AbstractElectrical 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

AbstractGallium‐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

AbstractThis 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

AbstractInfrared 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

AbstractThe 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

AbstractBoth 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

AbstractThe 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

AbstractThin 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

AbstractThe 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

AbstractA 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

AbstractThinning 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

AbstractThe 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

AbstractCalcium 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

AbstractThe 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

AbstractDefect 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

AbstractThe 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

AbstractA 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.