bluuebunny/crossref_metadata_2025 huggingface dataset:
Dielectric Properties of Tin Oxide Thin Film Capacitors
Authors: Kumar J. Siva , Rao U. V. Subba
Published: January 2007

Thin films of several thicknesses in the form of MIM structures are prepared from the powders of tin oxide (SnO2) by thermal evaporation technique in a vacuum of 10−5 Torr. The dielectric properties of tin oxide film capacitors have been studied with temperatures varying from 77 to 400 K and also with frequency. At 77 K the values of capacitance and loss tangent are small for these films. With increasing temperature the values of capacitance and loss tangent increase. The capacitance‐temperature plots show peak values of capacitance at 345 K for 1 kHz, 350 K for 2 kHz, 360 K for 5 kHz and 368 K for 10 kHz. These peak values of capacitance can be eliminated by repeated heating and cooling of the structures. The activation energy for the migration of charge carriers is calculated for tin oxide films and is found to be 0.13 eV. The results obtained on the dielectric properties of tin oxide thin films are presented and discussed.
The Effect of Microstructure on Thermally Stimulated Luminescence of Y–Ba–Cu–O System
Authors: Reddy Katta Narasimha , Prasad T. S. P. L. N. , Rao U. V. Subba
Published: January 2007

Thermally stimulated luminescence of Y – Ba – Cu – O (YBCO) samples in as‐prepared, quenched and water treated conditions have been studied. The TSL spectrum is observed to be different for these samples. Quenched and water‐treated samples are expected to decompose into a number of insulating phases. Identification of such phases using thermally stimulated luminescence is attempted.
Deformation Phenomena in n‐Pentadecanoic Acid Crystals
Authors: Prasad P. B. V.
Published: January 2007

The formation of heat induced fracture‐like patterns, slip‐twin promoted deformation, some epitaxial relations are discussed in case of n‐pentadecanoic acid crystals, grown from solutions, by solvent evaporation methods.
On Chemical Kinetics of Silicon Deposition from Silane (V) The Effect of Hydrogen Formation
Authors: Kühne H.
Published: January 2007

In consequence of hydrogen formation during silane pyrolysis total gas volume increases, when the reaction proceeds at constant total pressure. Any mole of silane decomposed produces two moles of hydrogen. In the present paper expressions are derived for 1st and 0.5th reaction order describing axial growth rate distribution of the isothermally proceeding reaction for the condition of constant total pressure. Those theoretically expected distributions are compared with results obtained by way of experiment on the one hand and those theoretically expected for the condition of constant gas volume on the other. It is concluded that the experimental results discussed rather agree with constant gas volume than with constant total pressure conditions. So, a compensating increase of total pressure along the tube axis might be supposed.
Thermoelastic and Piezoelastic Properties of Hexagonal RbMnCl3
Authors: Jeong S. , Haussühl S.
Published: January 2007

Temperature and pressure derivatives of the elastic constants, indices of refraction, dielectric constants, Faraday effect and thermal expansion of RbMnCl3 near Tc = 278 K confirm the existence of a second‐order phase transition. A strongly anomalous behaviour is observed with the elastic shear stiffness c44 which possesses a positive temperature derivative and a negative pressure derivative. These properties and also the pressure derivative of the transition temperature, dTc/dp = 6.2 K kbar−1 closely resemble the anomalous behaviour of two other ferroelectric species, betaine borate and betaine hydrogen maleinate.
Thermal Expansion and Oxygen Nonstoichiometry in High‐Tc YBa2Cu3Ox Superconductor
Authors: Olekhnovich N. M. , Zhabko T. E. , Orlova N. S. , Janovich V. D. , Pashkovskii O. I. , Zykova T. L.
Published: January 2007

The lattice parameters as well as the axial thermal expansion coefficients for YBa2Cu3Ox superconducting oxide ceramics with different oxygen content ranging from × = 6.14 to × = 6.95 are determined as a function of temperature between 80 and 400 K using X‐ray powder diffractometry technique. The effect of oxygen concentration on the thermal expansion behaviour is regarded. The values of α are found to decrease with the oxygen content reducing and depend on the condition of heat treatment. The essential anisotropy of thermal expansion is shown to exist, with αc being larger than αa and αb. The relationship between αa and αb depends both on the sample preparation conditions and temperature.
Applied Infrared Photoluminescence in Lead Salt Crystals
Authors: Schmidt H. , Fleischer T. , Sumpf B. , Szczerbakow A. , Herrmann Ka. , Tomm J. W.
Published: January 2007

Results on applied infrared photoluminescence investigations of lead salt chalcogenides are presented. Interpretations of spectra and wafer maps are given. The results obtained may be applied to the investigation of material properties important for laser and detector fabrication.
Some Results of the Analytical Evaluation of Isothermal Resistivity Measurements with Al – Zn – Mg Specimens
Authors: Oettel W. , Fabian H.‐G.
Published: January 2007

Isothermal measuring curves of a series of Al‐4.5 at.% Zn‐X at.% Mg (X = 0.2, 0.5, 1.0, 1.5, 2.25, 3.0) were evaluated analytically by means of the Johnson‐Mehl‐Avrami equation. Itturned out to be possible to fit the curves completely only by assumption of two process stages. The course of the parameters obtained their dependence upon the Mg content is interpreted by means of suitable model assumptions.
Structure and Packing in Smectic E and Smectic A Phases in the Series of 4‐n‐Alkyloxy‐4′‐alkanoylbiphenyls
Authors: Diele S. , Tosch S. , Mahnke S. , Demus D.
Published: January 2007

By means of X‐ray investigations the structure of the SE and SA‐phases of the title compounds has been studied. The lattice parameters of the orthorhombic SE structure are given. The thickness of the smectic layers is nearly the same in the SE and SA phases and agrees well with the length of the molecules in their most stretched form. That suggests a similar conformation of the alkyl chains in both phases. A model of the packing in the SA phase is discussed which is based on a dense packing with antiparallel orientation of molecules with a non‐symmetrical shape.
Effect of Supersaturation on Disappearance of Faces of Growing Crystals
Authors: Szurgot M.
Published: January 2007

Growth conditions affect the velocities of disappearance and lifetime of faces of growing crystals. Supersaturation is a factor which causes either an increase or a decrease in velocities of disappearance of faces and their lifetime depending on the mechanism and kinetics of growth of disappearing and adjacent faces. The possible relationships between velocities of disappearance of faces, their lifetime and supersaturation have been derived and discussed.
The Growth of Some Aromatic Hydrocarbons Single Crystals from the Melt
Authors: Marciniak B.
Published: January 2007

The present work summarizes results concerning growth of anthracene, pyrene, p‐terphenyl, carbazole, and phenanthrene single crystals by Bridgman method. The temperature conditions and rate of crystal growth as well as seeding conditions have been determined and discussed in the aspect of purity grade of considered materials.
The Lithium Niobate Piezooptical Features
Authors: Mytsyk B. G. , Pryris Y. A. V. , Andrushchak A. S.
Published: January 2007

Piezooptical effect (POE) in LiNbO3 crystals is analytically described considering crystallophysical axes of positive directions choice. All the piezooptical coefficients have been determined and correlation of the absolute piezooptical coefficients (POCs) and coefficients, describing stress‐induced birefringence, has been carried out. The POE indicating surface sections, which adequately reflect the anisotropy effect, have been constructed.
On the Formation of Titanite
Authors: Steinike U. , Uecker D.‐Chr. , Köhler Th. , Plötner W. , Schierhorn E. , Jancke K. , Hennig H‐P.
Published: January 2007

The formation of titanite (CaTiSiO5) out of the starting materials quartz and titanate (CaTiO3) is investigated in dependence on the mechanical activation. The formation temperature may be lowered by the use of mechanically disturbed quartz. There are optimal conditions for the reaction concerning the mechanically generated disorders. Cristobalite is an intermediate. The formation of titanite is ascribed as one‐sided bulk diffusion of Ca‐ and Ti‐ions (or corresponding oxygen complexes) into a quartz lattice being in the state of transformation and as a surface reaction of Si‐ions (or corresponding oxygen complexes) on the titanate surface.
Synthesis and Structural Characterisation of 2‐Aminoacetophenonesalicylaldazine Complexes of Some Bivalent Transition Metal Ions
Authors: Singh B. , Singh U. R.
Published: January 2007

Metal(II) complexes M(aas)2 [M = Mn. Co, Ni, Cu and Zn, Haas = 2‐aminoacetophenonesalicylaldazine] have been prepared and characterized. Magnetic and spectral data such as electronic, ESR, and IR are used to establish the stereochemistry and mode of bonding of azine in the complexes. X‐ray diffraction study suggests orthorhombic unit lattice for Co(aas)2, Ni(aas)2, Cu(aas)2 and Zn(aas)2 complexes.
A Study on the First Order Phase Transitions in Hydrocarbon Crystals
Authors: Prasad P. B. V.
Published: January 2007

A polarization hot stage microscopy study was made on the phase transitions in n‐octacosane and n‐hexatriacontane hydrocarbon crystals. Advancement rates of transition fronts of high temperature phase in low temperature phase were measured. Transition in the interior layers was detected. In order to explain the observations, we propose a model, which involves intrachain defects in the extended chain configuration. This model is an advanced stage of the model proposed by STROBL, basing on the SAXS results.
The Spontaneous Strain in an Aluminate Sodalite System Determined by Synchrotron and Sealed Tube X‐radiation
Authors: Melzer R. , Hu X. , Pennartz P. U. , Löchner U. , Depmeier W.
Published: January 2007

Lattice parameters in the mixed aluminate sodalite system (Ca1‐xSrx)8 [Al12O24] (CrO4)2 have been determined on the Aachen/Frankfurt (Darmstadt)/Tübingen powder diffractometer at DESY/Hasylab, Hamburg, FRG, with synchrotron radiation (SR) of a wavelength of γ = 1.383 Å. From these data the values of the spontaneous strain for tetragonal and orthorhombic samples were calculated. The synchrotron data were compared with those obtained by using a conventional Guinier camera with sealed tube CuKα1 X‐rays. In the mixed system a concentration range Δx of abcut 4 mol%, i.e. in the composition range x from 0.23 to 0.27, exists, in which the conventional technique still indicates cubic symmetry, whereas synchrotron data clearly exhibit tetragonal peak splitting. In order to determine the phase diagrams of mixed aluminate sodalites – or of comparable systems – and to interpret the physical properties of the phases correctly, sealed tube X‐rays are of limited value. Availability of SR beamtime is a crucial factor in the experiments.
Thickness Dependence of Electrical and Structural Properties of FTO Films
Authors: Amanullah F. M. , Pratap K. J. , Babu V. Hari
Published: January 2007

Fluorine (0.8 M) doped tin oxide films of various thicknesses were prepared on heated glass substrates (520 °C) by spray pyrolysis technique. The chemical and thermal stabilities of FTO films were found to be very good. The characterization has been done by XRD and found to agree with the reported results. As thickness of the film increases, intensities of peaks increased. From the X‐ray diffraction data, grain size of the crystallites have been calculated. The electrical and structural properties were studied for different thicknesses. Hall measurements showed that thicker films have relatively high Hall mobilities compared to those of thinner films. The high carrier concentration showed that the films are degenerate. The relationship between carrier concentration and Hall mobility revealed that the ionized impurity scattering centres were the dominant cause of scattering.
Doping of GaAs with Donor Impurities Te and Sn during Liquid Phase Epitaxy from Mixed Gallium  Bismuth Melts
Authors: Yakusheva N. A. , Pogadaev V. G.
Published: January 2007

The electrical properties of GaAs epilayers doped with donor impurities Te and Sn during LPE from mixed Ga  Bi melts in temperature intervals from 850 to 820 °C and from 700 to 630 °C were investigated. The analysis of incorporation of Te and Sn into crystallizing GaAs considering preliminary association of impurity and compound component atoms in the liquid agree satisfactory with experimental data providing the presence of additional concentration of nonequilibrium arsenic vacancies on the (111)B surface of growing layer, which is not conditioned by activity of compound components in the liquid. It is shown that the main factor, determining the incorporation of donor impurities Te and Sn into GaAs during epitaxy from mixed Ga  Bi solvents, is the change of Ga and As concentrations ratio in the liquid.
A Semiclosed Technique of Zinc Diffusion in InP
Authors: Krieghoff T. , Nowak E. , Kühn G. , Schumann B. , Höpner A.
Published: January 2007

A novel semiclosed diffusion technique for InP has been developed. As diffusion source an InP wafer evaporated with a thin layer of metallic zinc was used. The source is separated at a distance of 150 μm from the sample. The dependence of the zinc concentration and the free‐hole concentration on the thickness of the zinc layer and the time was investigated. The technique makes it possible to obtain free‐hole concentration of (8 ± 2) · 1018 cm−3.
Growth Kinetics of Adenine Sulphate Crystals
Authors: Zachovà Jana , Nitsch K. , Matuchovà Marie , Durchan M.
Published: January 2007

The kinetics of growth and dissolution of adenine sulphate in 1.5 mol · 1−1 H2SO4 at different super‐ and undersaturations has been studied. The solubility of adenine sulphate in H2SO4 was determined over the temperature range 20–50 °C. The growth rate of the (100) face is by about 25% higher than that of (111) and the crystal habit is changed by a high supersaturation almost to a bipyramide. The surface diffusion was determined as a prevailing processes and the BaS model gives the best fit with experimental data.
A Study of the Nucleation Kinetics, Linear Growth and the Overall Crystallization Kinetics of Meltspun Pd80Si20 Amorphous alloy
Authors: Spassov Tony
Published: January 2007

Nucleation kinetics, linear growth rate and overall isothermal crystallization kinetics of PdSi amorphous alloy are studied by means of DSC and optical microscopy. It is found that both the histograms of the crystallite sizes and the DSC isotherms (resp. the time dependences of the degree of transformation α(t)) are best described by the model comprosing the simultaneous occurrence of two reactions of crystallization: heterogeneous as well as homogeneous non‐stationary nucleation with subsequent three‐dimensional growth in both cases.

From the fit of the experimentally measured and the calculated according the model thus proposed distribution curves Ni(Φ) the stationary rates of heterogeneous and homogeneous nucleation, the number of quenched‐in nucleation sites and the transient time lags of heterogeneous and homogeneous nucleation have been estimated. Using the values of these parameters kintic curves degree of transformation vs. time have been generated, which are closed to the exerimental x(t) curves obtained by means of DSC at isothermal conditions.
Synthesis and Size Optimization of Crystals Grown by the Mixed Gel‐Solution Technique
Authors: Santos A.
Published: January 2007

Two experimental devices have been used with the aim to optimize the synthesis of single crystals by means of the mixed gel‐solution technique. These consist of a gel source‐reservoir saturated at T0 and a vessel of aqueous solution saturated at Tf. T0 > Tf. In such devices, the evlution of the supersaturation in the vessel of aqeous solutions allows that the grwoth process to be controlled by such a source‐reservoir and the crystal itself. Average growth rates of 3 and 4 mm/day have been found for KDP crystals.
Influence of Second and Further Neighbours on the Presence of Faces in Crystal Habit
Authors: Prywer Jolanta
Published: January 2007

Influence of growth volocities of further neighbours on the presence of faces in crystal habit has been analysed. It was established that the consecutive neighbour affects the face size only after the disappearance of the previous neighbour. The formula for the critical growth velocity governing disappearance of a face which includes the closest and further neighbours has been derived and discussed.
Investigation of the Solution Status of TGS and ATGSP Crystals
Authors: Wang O. W. , Fang C. S.
Published: January 2007

This paper reports on the solubility curves of TGS and ATGSP crystals with different pH's. The relationship of (010) growth rate in solutions with different pH varied with the supersaturation, has been studied. The influence of pH on the metastable region of solution have been measured. The experimential results are discussed with respect to the structure and viscosity of solution and the solubility of the crystals. Finally the optimum conditions for the rapid growth of TGS and ATGSP crystals is given.
Thomas‐Fermi Dielectric Screening in Some Binary Semiconductors
Authors: Shajan X. Sahaya , Mahadevan C.
Published: January 2007

Thomas‐Fermi (TF) dielectric functions. ϵ(k) and ϵ(r) have been estimated for some binary semiconductors. TF functions obtained are found to be in excellent agreement with those calculated by the empirical pseudopotential method.
Light Intensity Variation Studies of MoS2/Electrolyte Interface
Authors: Patel S. G.
Published: January 2007

Photoelectrochemical characterization of natural and synthetic molybdenum disulphide prepared by direct vapour transport technique have been carried out. The quality of the MoS2/electrolyte junction for photovoltatic applications was assessed examining the effect of varying light intensity on current voltage behaviour. For measurements at low intensity a broad light source was used. The ideality factor (n) was determined for these junctions by modelling the MoS2/electrolyte junction in terms of a Schottky barrier. The effect of intensity in the efficiency of the PEC solar cells has also been studied in detail. All the observations have been described and the implications have been discussed.
Growth and Characterization of Direct‐connecting AlGaAs/GaAs TJS Light Emitting Device on SI GaAs Substrate by LPE
Authors: Chang L. B. , Lan H.
Published: January 2007

High output power (above 3 mW/facet) AlGaAs/GaAs Transverse‐Junction Stripe light emitting diodes have been grown on Semi‐Insulating (100) GaAs substrates by Liquid Phase Epitaxy. these light emitting diodes utilize a “Direct‐connecting” transverse‐junction stripe structure, which can confine the transverse‐current and reduce the series resistance. By thinning the thickness of the “effective active‐layer” of this structure, a room‐temperature pulsed lasing operation is also achieved with a threshold current as low as 35 mA and a peak wavelength around 904 nm. This “Direct‐connecting” transverse‐Junction Stripe light emitting device with a Metal‐Semiconductor Field Effect Transistor on an electrical isolated semi‐insulating substrate in the future.
Initial Growth Stages of Man‐made Quartz Crystals and Growth Mechanism of their (0001) Face
Authors: Kirov G. K.
Published: January 2007

In a series of short term runs it has been shown that in the course of the non‐stationary part of the hydrothermal process the quartz seed plate is subject to: 1. fast and deep dissolution; 2. very slow dissolution‐and‐growth; 3. a shallow complementary etching; 4. mass formation of crystallization centres; 5. tangential and normal growth of these centres accompanied by their aggregation into larger growth units. Every one of theses processes produces a specific structure on the actively growing (0001)‐face. The last process which continues also when the temperatures are stationary, creates the well known “cobble structure”. As the growth continues the prolonged aggregation increases perceptibly the growth rate and makes the cobble structure coarser and coarser.
Radial Distribution Analysis of the Structural Disordering in Mechanically Treated Silicon Powder
Authors: Šepelák V. , Tkáčová K. , Števulová N.
Published: January 2007

The changes in structure brought about by energy‐intensive planetary grinding of silicon were investigated. The interpretation of the RDF obtained by X‐ray diffraction analysis lead to the conclusion that the mechanically treated silicon is in a partially crystalline state. The spatial arrangement of the Si atoms is disturbed in a radial distance around 0.47 nm. The diametral size of the preserved regions d < 0.94 nm exceeds almost twice the size of the unit cell of Si and is of the same range as the size of crystallites in the mechanically treated silicon powder.
The Nature of As‐related Defects in Semi‐Insulating GaAs Bulk Crystals
Authors: Mo P. G. , Wu J. , Fan X. Q. , Zhu J. , Zhou Y. D. , Tan H. Z.
Published: January 2007

The behaviour of As‐related defects in SI (semi‐insulating) GaAs are studied from the viewpoint of the origination of As‐related precipitates, generation and evolution of EL2 during postgrowth and the possible defect interactions involved EL2 variation under As overpressure annealing. The precipitates were identified as elemental As and As‐rich GaAs polycrystalline grains and their features depend on the growth process. A defect interaction model has been proposed on the generation/annihilation of EL2 assigned as AsGa VAs VGa complex respect to non‐stoichiometry such as Asi VGa and VAs.
LPE Growth of GaInAsP/InP Heterostructures for 1.3 μm Planar Buried Mesa Lasers
Authors: Novotný J. , Procházková O.
Published: January 2007

LPE heterostructure growth processes devised to prepare GaInAsP/InP planar buried mesa ridge (PBMR) lasers are described. A combination of supercooling and two‐step cooling regimes of LPE was used to grow InGaAsP/InP heterostructures with the active layer flanked by two waveguiding layers. The optical waveguide geometry was optimised to yield minimum threshold current density. Low‐temperature (600°C) LPE process was employed to regrow the etched mesa structure. The prepared PBMR laser devices with optical resonator lengths of 250 μm exhibited room temperature threshold current values near 20 mA and T0 values in the range 60–70K. Optical power‐versus‐current characteristics were linear up to 25 mW.
Crystal Structure of 1‐(2‐Pyridylmethyl)‐2,4,6‐Triphenyl‐Pyridinium Perchlorate
Authors: Farag I. S. Ahmed , El‐Shora A. I. , Abdel‐Megeed M. F. , Rybakov V. B.
Published: January 2007

The crystals of 1‐(2‐pyridymethyl)‐2,4,6‐triphenylpyridinium perchlorate are monoclinic, space group P 21/b. The unit cell parameters are a = 18.941(5), b = 19.502(6), c = 15.135(5),y = 115.99°(2), Z = 8, d0 = 1.31(3), dx = 1.319 g/cm3. The structure has been determined by direct methods and refined by block diagonal least squares to R0 = 0.08 for 2520 reflections. The phenyl rings in both molecules (I) and (II) are planar. These rings are twisted with respect to the central pyridyl rings.
Thermodynamic Evaluation of the Nickel‐rich Part of the NiZn‐System
Authors: Vassilev George P.
Published: January 2007

Optimization of thermodynamic and phase diagram data about the solid and liquid NiZn solutions is performed. The temperature and concentration dependence of the Gibbs free excess energy is described by means of second degree polynomials. The calculated liquidus and solidus curves have been compared to the experimental ones.
High‐pressure Synthesis and Properties of Manganates with Ilmenite Structure
Authors: Troyanchuk I. O. , Derkachenko V. N. , Shapovalova E. F.
Published: January 2007

A2+Mn4+03(A  Ni, Co, Mg, Cu) manganates with ilmenite structure have been obtained by solid phase synthesis at high pressure and temperature. The synthesis conditions for single phase samples have been determined, and investigations of the magnetic, electric, magnetooptic, and resonance properties were carried out.
LPE Growth of Ga1 – xInxSb Multi‐grading Layers
Authors: Xiuying Gong , Okitsu Kazuhiko , Ozawa Tetsuo , Hawakawa Yasuhiro , Yamaguchi Tomou , Kumagawa Masashi
Published: January 2007

Electronegativity difference approach (ENDA) has been successfully employed to obtain good prediction of the In atomic fraction, energy bandgap and lattice constant of the Ga1 – xInxSb/Ga1 – yInySb/GaSb system. Nearly lattice‐matched GalnSb epilayers with In atomic fraction of 0.42 have been obtained by the liquid phase epitaxy. The cut‐off wavelength was 2.2 μm at room temperature.
Gettering Properties of Praseodymium in InGaP LPE Growth
Authors: Lai M. Z. , Chang L. B.
Published: January 2007

Praseodymium (Pr) is added to the InGaP growth melt during Liquid Phase Epitaxy (LEP) for the first time. The epilayers are grown by using a supercoling method, on (100) Cr‐doped Semi‐Insulating (SI) GaAs substrates at a growth temperature of 790°C. An examination of the electrical properties reveals that, depending on the amount of Pr in the growth melt, n‐tpye InGaP epilayers with room temperature electron concentrations in the range of 3.4 × 1016 cm−3 to 5.3 × 1015 cm−3 and electron mobilities from 730 to 1310 cm2/Vs can be prepared. The photoluminescence spectral results show that by increasing the amount of Pr in the growth melt, smaller Full Width at Half Maximum (FWHM) values and better band edge (BE) recombination intensities result.
Nuleation and Growth of Thin Ag Films Vacuum‐deposited onto W
Authors: Michailov E.
Published: January 2007

An attempt to analyse the nucleation and growth phenomenon in a typical “Stranski‐Krastanov” (SK) growth system ‐ Ag/W (PAUNOV, MICHAILOV 1979; MICHAILOV), in terms of island growth theory was made. Ag‐layers were analysed by the use of scanning electron‐and optical microscopes. A strong dependence of the nucleation kinetics on supersaturation and grain orientation was found to exist. On the basis of known rate equations, the number of atoms in the critical cluster i and the value of nucleation potential barrier E were estimated. The comparison between the experimentally obtained size‐, first nearest neighbour‐ and radial distributions and theory shows that: 1) nucleation and growth processes proceed through a surface diffusion of the atoms; 2) no coalescence between the crystallites and no crystal mobility exist.
Debye‐Waller Factors and Elastic Constants for Beryllium Oxide at Temperatures between 10 and 720 K (I). Anisotropy of Inoic Mean‐Square Displacements
Authors: Sirota N. N. , Kuzmina A. M. , Orlova N. S.
Published: January 2007

The Debye‐Waller factors and the mean‐square dynamics displacements of the Be and O ions in beryllium oxide are obtained from X‐ray diffraction powder data over the temperature range from 10 to 720 K for different crystallographic directions. The observed anisotropy of these mean‐square displacements is discussed.
Determination of the Rotational Viscosity and of the Elastic Constant from Measurements of Switching Times and Threshold Voltage on Planar Oriented Sc Phases
Authors: Dierking I. , Giesselmann F. , Zugenmaier P. , Pelzl G. , Schiller P.
Published: January 2007

The Freedericksz transition of planar oriented Sc phases was studied experimentally with an electrooptical method and the theoretically predicted reorientation along the Sc tilt cone confirmed. Measurements of the threshold voltage and the switching times lead to the determination of the rotational viscosity and the elastic constant for five selected compounds with positive dielectric anisotropy.
A First Approach to CVD Si1–xGex Layer Growth by Means of Chemical Reaction Kinetics
Authors: Kühne H. , Morgenstern Th.
Published: January 2007

A reaction mechanism will be suggested for interpreting Si1–xGex CVD layer deposition from a silicon source and germane reaction gas mixtures in order to explain the observed silicon layer growth increase in consequence of the presence of germane. A successive substitution of the hydrogen atoms available in germane molecules by silyl groups forming a silicon containing intermediate of germane will be assumed. It will further be supposed that both the original silicon source and the germane intermediates will independently be decomposed by chemical reactions leading to Si1–xGex CVD layer deposition from dichlorosilane‐germane‐hydrogen reaction gas mixtures at temperatures in the range of 600 ≦ T(°C) ≦ 900 as recently published by KAMINS and MEYER.
A Gamma‐ray Diffraction Study of MBE‐Grown CaF2/Si(111) Heterostructures
Authors: Kurbakov A. I. , Rubinova E. E. , Sokolov A. E. , Mäder M. , Tempel A. , Tobisch J.
Published: January 2007

MBE grown epitaxial films of CaF2 onto Si(111) substrates were investigated by gamma ray diffraction to obtain assertions about the real structure and the strain situation in the epitaxial systems. It were measured the integral reflection coefficient Ri and the angle distribution of the reflected intensity of both (111) and (333) reflections. It was found that (i) a high temperature annealing step during the wafer preparation (1200 °C) causes a drastical increase of real structure defects in the substrate material, (ii) expitaxial layers of 18 nm thickness are grown pseudomorphically, layers having a thickness of 30 nm are relaxed, (iii) the misfit dislocation network formed during the relaxation process is localized not in the deposit but in the substrate material.
Crystal and Molecular Structure of an Oligomeric 1:2 Complex of Copper (II) Azide with 4‐Methylpyridine
Authors: Goher M. A. S. , Mautner F. A.
Published: January 2007

A 1:2 complex of copper (II) azide with 4‐methylpyridine has been synthesized and the crystal structure has been determined by X‐ray methods. The compound crystallizes in space group P21/a with a = 11,062(3), b = 19.310(6), c = 20.547(5) Å, β = 90.83(2)°, V = 4389(1) Å3, Z = 12 and R = 0.048 for 959 observed MoKα data. The structure is built up by oligomeric edge‐sharing chains of polyhedra. With the exception of a single coordinated azido group, all other azido ligands serve to bridge neighbouring copper centers [at Cu  N bond distances of 1.94(2) to 2.76(2) Å] in the μ(1,1) fashion.
A Mössbauer Study of the Interaction between Fe2O3 and TeO2
Authors: Gospodinov G. , Peev T.
Published: January 2007

The interaction between Fe2O3 and TeO2 by vacuum sintering at various temperature was studied The compounds obtained were identified by means of Mössbauer spectroscopy. The conditions for the synthesis of Fe2 Te4O11 were found. Some influence of the experimental conditions was established.
Phase Transition Studies in Some 4‐n‐Alkyl‐N‐(4‐n‐Alkyloxy‐Benzylidene)‐Anilines
Authors: Rao P. Bhaskara , Potukuchi D. M. , Murthy J. S. R. , Rao N. V. S. , Pisipati V. G. K. M.
Published: January 2007

The results of phase transition investigations in two homologous series of 4‐n‐alkyl‐N‐(4‐n‐alkyloxy‐benzylidene)‐anilines, viz., 60. m and 70. m compounds using thermal microscopy, differential scanning calorimetry, density and refractive index measurements are reported. The nature of the order of various phase transitions and the pre‐transitional effects in the fluctuation dominated non‐linear regions in the vicinity of IN, IA and NA transitions are discussed in the light of the available data on other nO. m compounds.
Study on the Sensitization of Ce3+ to Nd3+ in YAIO3
Authors: Shenghui Yan , Guoqiang Yan , Yongcheng Zhong
Published: January 2007

This paper presents the absorption spectra, excited spectra and fluorescence spectra of Nd: YAP, Ce: YAP and Nd, Ce: YAP. It is believed that there is an energy transfer from Ce3+ to Nd3+ and it is possible to improve the laser efficiency of Nd: YAP sensitized by Ce3+.
Physical Properties of K2ZnCl4
Authors: Jeong S. Y. , Jang M. S. , Han S. K. , Haussühl S.
Published: January 2007

Large single crystals of orthorhombic K2ZnCl4 with optical quality have been grown by the Czochralski method. The elastic constants and their temperature and pressure derivatives have been determined from ultrasonic resonance frequencies of thick plates of different orientation and the shift of these frequencies induced by temperature and pressure changes, respectively.

K2ZnCl4 shows a small elastic anisotropy. Measurement of the dielectric constant was made along the ferroelectric axis εa in the temperature from 303 K to 573 K. εa of K2ZnCI4 grown by the Czochralski‐method shows a smaller thermal hysteresis at the incommensurate‐commensurate transition point (403 K) than that of crystals grown from an aqueous solution. It explains that crystals grown by the Czochralski‐method are more purified, the pinning effect is weakened. The thermal hysteresis occurs with the same width at 10 KHz, 100KHz, 1 MHz and 10 MHz.
Growth and Spectrometric Tests on Bi4Ge3O12 Crystals
Authors: Dafinei I. , Mitroaica Gh. , Angelescu T. , Niculescu I.
Published: January 2007

A resistance‐heated furnace with a good control of temperature gradients is used for the Czochralski growth of precipitate and colour free Bi4Ge3O12 (BGO) crystals up to 30 mm in diameter and 80 mm in length from a 45 mm diameter crucible. The quality of the grown crystals is discussed in connection with the growth conditions.

Spectrometric tests made on scintillators obtained from BGO crystals are presented. A Monte Carlo program is used in order to compute the full energy peak efficiency of the detector for different energies and geometries. The computed values are compared to the experimental results.
Crystal Growth of Lead (II) Iodide from the Melt
Authors: Eckstein J. , Erler B. , Benz K. W.
Published: January 2007

Bulk Pbl2 crystals up to 20 cm3 have been grown from high purity source material in a controlled way using a modified Bridgman‐Stockbarger technique. The cleavage plane (0001) of crystals grown by a natural seed selection in a tipped‐end ampoule is nearly parallel to its axis. On a mica substrate epitaxially grown crystals cleaved perpendicularly to the axis of a specially designed double wall ampoule.
Crystallizaton Characteristics of the Alternating Tetrafluoroethylene‐Ethylene Copolymer
Authors: Dobreva A. , Nikolov A. , Kostov G.
Published: January 2007

The alternating tetrafluoroethylene‐ethylene (TFE‐E) copolymer has been studied with respect to its crystallization by using differential scanning calorimetry and optical microscopy. The value of the specific surface energy σ at the melt/crystal interface is calculated to be about 2 · 10−3 J/m2. The nucleating activity Φ of TiO2 particles introduced into TFE‐E copolymer is estimated to be approximately 0.9. The temperature dependence of the nucleation rate and of the linear growth velocity are constructed in the whole region from the melting temperature Tm to the vitrification temperature Tg. The minimum cooling rate for the formation of a crystal‐free TFE‐E copolymer glass is calculated and its value amounts to 104 K · min−1.
A Thorough Reconsideration of in‐situ Doping Theory of Epitaxial Silicon Layers
Authors: Kühne H.
Published: January 2007

The adsorption‐desorption limited doping mechanism as suggested by REIF and DUTTON to explain in‐situ doping of epitaxial CVD silicon layer will thoroughly be discussed in comparison to the more general transport‐reaction limited mechanism as originally suggested by SHEPERD, Distinctive and common features will be highilighted and discussed with respect to composite layer growth.
On the Critical Growth Velocities for the Presence of Faces on Growing Crystals
Authors: Szurgot Marian
Published: January 2007

Faces of three‐dimensional crystals have been divided into edge and corner ones to describe the phenomenon of their disappearance and appearance during the crystal growth. The expression for the critical growth velocity governing the presence of corner faces has been derived and verified and the validity of the previous relationship (SZURGOT, PRYWER) for the edge faces confirmed. Three nearest neighbours control the presence of corner faces and two neighbours decide on the edge faces.
X‐ray Characterization of Defect Structure in LEC Annealed GaAs Crystals
Authors: Czekalski T. , Zielińska‐Rohozińska E.
Published: January 2007

Wafers of commercially available semi‐insulating (SI) Czochralski‐grown GaAs crystals have been annealed at temperatures near the melting point (> 1100 °C) both for relatively short and long time and then rapidly quenched into cold water. Heat‐treated crystals have been investigated by X‐ray transmission diffraction topography. Cellular structure pattern of the as‐grown sample is replaced by images of precipitates spread out over whole sample. This suggests that the excess arsenic condenses as As precipitates with nucleation sites not correlated with cell walls.
The Polytypoidic Structure of the High‐Tc Superconducting System Bi2Sr2Can–1CunO2n+4 and its Superconductivity
Authors: Hengnan Zhou , Yuanjin Lu
Published: January 2007

The polytypoidic structures in the Bi‐system of superconductors characterized by X‐ray, electron diffraction and TEM technique are described. A strong incommensurate modulated diffraction was observed by these methods in the 2223‐phase. In addition, we revealed the Laue streaks for the one‐dimensional disorder, the banded structure perpendicular to the c‐axis. We suppose that the intergrowth is an indication of the displacement in the Bi‐O layers. It is evident that the polytypoidic concept allows us to describe the structure and physical properties of these superconducting phases in a unified manner. So it is shown that the polytypoidism is a general feature of the Bi‐system materials.
Electron Paramagnetic Resonance of VO2+ in M2Zn(SeO4)2 · 6H2O(M=K, Rb) Single Crystals
Authors: Saroj  , Yadav S. K. , Jain V. K.
Published: January 2007

The EPR spectrum of VO2+ has been studied in single crystals of K2Zn(SeO4)2 · 6H2O and Rb2Zn(SeO4)2 ∼ 6H2O at ∼9.45 GHz. VO2+ substitutes for Zn2+ have preferential orientations in the lattice. The V = O of the intense vanadyl center is nearly along the longest ZnH2O direction. Spin‐Hamiltonian parameters have been evaluated from single crystal as well as from powder spectra.
Polarizabilities of Binary Mesophase Mixtures Containing 4,4′‐Di‐Ethoxy‐Azoxybenzene
Authors: Reddy R. N. V. Ranga , Murthy V. R.
Published: January 2007

The applicability of the modified Lippincott‐δ‐function model (ML δ P) method is tested for binary mesophase mixtures. Using this method, the polarizabilities, polarizability anisotropies and order parameters of binary mesophase mixtures containing 4,4′‐di‐ethoxy‐azoxybenzene are evaluated and compared with the reported values. A close agreement is observed between the estimated values and reported values.
Crystal Structure and Growth Morphology of Nickel Superthin Films
Authors: Mikhailov I. F. , Borisova S. S. , Fomina L. P. , Babenko I. N. , Melnik N. N. , Pudonin F. A.
Published: January 2007

Ni superthin films of t = 0.3–3.5 nm thickness prepared by radio‐frequency sputtering have been studied by mordern X‐ray methods, such as reflectometry, fluorescence analysis and grazing‐beam structure analysis. The results have shown that the films were polycrystalline and their densities correspond to bulk values for nickel already at the early stage of growth. None oxides were found in Ni films. The model of earliest stage film growing have been suggested: film begins to grow by the island mechanism, but the crystallization front remains perfectly plane during the growth.
Preparation of High‐quality InGaAsP/InP Heterostructures for Edge‐emitting 1.3 μm LED's
Authors: Novotný J. , Vyhnalík L. , Zelinka J.
Published: January 2007

Effects of varying the composite heterostructure geometry have been investigated in the context of InGaAsP/InP (λ λ= 1.3 μm) non‐coherent radiation sources. The study has been guided by a preliminary theoretical analysis and complemented by evaluation of the statistics in sample ensembles. Optimum construction diodes emit 600–700 μW/facet of optical power. The added quaternary layer of intermediate bandgap (Λg λ= 1.1 μm) has been found to have benefical effect on the quantum efficiency and reproducibility of the manufacturing process.
On the Chemical Reaction Mode of Polysilicon Deposition from Silane
Authors: Kühne H.
Published: January 2007

Silane decomposition and silicon layer growth will be described by way of theory taking into account heterogeneous as well as homogeneous reaction mode and 1st as well as 0.5th order of the chemical reaction. Comparing axial layer growth rate distribution and total substrate surface area effect on the latter with respect to theoretical and experimental results (for the process conditions investigated), it will be shown that the deposition of undoped poly silicon is characterized by a heterogeneous reaction mode, whereas chemical reaction is of first reaction order in the temperature range above 973 K and of 0.5th reaction order below 973 K. The deposition kinetics of strongly in‐situ phosphorus doped poly silicon is shown to be in agreement with a homogeneous reaction mode of 0.56th reaction order.
The Description of the Isothermal Decomposition Processes in AlSc Alloys by means of Electric Resistivity Measurements and TEM Investigations
Authors: Wolter R. , Siebert P. , Fabian H.‐G.
Published: January 2007

The decomposition behaviour of two AlSc alloys (cSc = 0.18; 0.36 at.%) after direct quench to room temperature and subsequent ageing at temperatures in the range 200 °C ≦ Ta ≦ 550 °C was investigated by means of isothermal resistivity measurements and TEM. In the temperature range 325 °C ≦ Ta ≦ 400 °C both alloys show independent of the Sc content an “inversion” of the decomposition kinetics, obviously caused by the transition of the coherent into the incoherent Al3Sc phase.
Near‐edge Optical Properties of CuInSe2 Studied by Photoacoustic Spectroscopy
Authors: Zegadi A. , Neumann H. , Slifkin M. A. , Tomlinson R. D.
Published: January 2007

Optical absorption spectra of n‐type CuInSe2 single crystals were evaluated by means of photoacoustic spectroscopy in the photon energy range from 0.94 to 1.02 eV. At photon energies below 0.99 eV the spectra exhibit exponential tails that are ascribed to the presence of shallow impurity states. At higher photon energies the absorption coefficients follow the relation for direct allowed optical transitions between parabolic bands. The parameters of this relation are determined and compared with previous measurements.
Quench Hardness Anisotropy of Rhombohedral Crystals. Sodium Nitrate
Authors: Joshi D. R. , Pandya J. R.
Published: January 2007

The effects of quenching temperature and orientation of Knoop indenter on microhardness of cleavage planes of synthetic sodium nitrate crystals are studied for the range of applied loads (20–160 g) in the high load region. Phenomenological approach was followed to obtain an empirical relation connecting Knoop hardness number, orientation, and quenching temperature. Anisotropic indices are also determined. The implications are discussed.
Hardness Anisotropy of Rhombohedral Crystals of Calcite. Variation of Hardness with Orientation
Authors: Joshi D. R.
Published: January 2007

The variation of hardness of rhombohedral single crystals of calcite with orientation of longer diagonal of Knoop indenter with respect to direction [100] on a cleavage plane (100) is studied. The Knoop hardness number H which has a constant value in the range of high loads (40–80 g) varies with orientation A and quenching temperature. By following phenomenological approach, an empirical relation √HA = mA + C is developed from these studies. The effects of crystal anisotropy and thermal treatment of specimens after indentation are also discussed.
Refractive Indices, calculated orientational order Parameters, and Polarizability Anisotropies of Liquid Crystalline 3‐(4‐Alkyl‐phenyloxy)‐propane‐1,2‐diols
Authors: Hauser A. , Hamann A. , Tschierske C. , Pelzl G.
Published: January 2007

For a novel variant of smectic structures the SA+ phase of the homologous 3‐(4‐alkyl‐phenyloxy)‐propane‐1,2‐diols the refractive indices ne and no were measured in dependence on the temperatue. The polarizability anisotropy, the orientational order parameter, and the packing fraction were calculated using a mean field fitting method. The components of the internal field tensor were included in the fitting procedure. The increasing mobility of the alkyl chain for higher homologues reduces the orientational order in the smectic layers and also the birefringence which is very small. The molecular polarizabilities are increasing nearly linearly with the elongation of the alkyl chain. The small alternation of the polarizabilities corresponds to the alternating change of the length‐to‐breadth ratio. The calculated packing fractions are enhanced for higher homologues.
Binary Systems of Swallow‐Tailed and Laterally Branched Liquid Crystals and their Dielectric Behaviour
Authors: Heinemann S. , Kresse H. , Weissflog W.
Published: January 2007

Swallow‐tailed liquid crystals were mixted with four laterally branched substances in order to investigate the influence of molecular geometry on the correlations of molecules in the short range order. Besides the isobaric phase diagrams the results of dielectric measurements on oriented probes in the frequency range from 10 Hz to 100 kHz are discussed. Microscopic as well as dielectric investigations show that laterally branched molecules destroy the antiparallel arrangement of swallow‐tailed substances and in this way destabilize the smetic A phase. It is possible to put in order laterally branched substances according to its “destroying” influence.
Effect of the Presence of Crystals on Nucleation Parameters
Authors: Nývlt J.
Published: January 2007

Metastable zone width measurements in aqueous solutions of 18 well soluble substances have been used for the characterization of the nucleation process in absence and in presence of crystals. As could be expected, it has been confirmed that the specific surface energy of the critical nucleus is only slightly decreased by the presence of crystals. The effect is almost negligible for the critical nucleus size. Both of these quantities can be correlated with the solubility of the substance.
Characteristic Growth Features and Etching of InBi Single Crystals
Authors: Pandya G. R. , Vyas S. M.
Published: January 2007

The characteristic growth features observed on the top free surface of InBi single crystals grown by the zone‐melting method are reported. These features are analysed by stereographic technique and a possible mechanism responsible for the appearance of the characteristic growth features is discussed. A new etchant capable of revealing dislocations inclined to the cleavage plane is also reported.
Further Investigation of the Growth of Spliced KDP Seeds and its Mechanism
Authors: Feng Pan , Jin‐Kui Liang , Gen‐Bo Su , You‐Ping He , Yi‐Sen Huang , Bing‐Rong Huang , Qing‐Lan Zhao
Published: January 2007

This work deals with the further study of the growth and mechanism by splicing some seeds, e.g. three seeds arranged in two kinds, four seeds, and n × n (n = 3,4) seeds, and furthermore a dish of pressed powder, which can be considered as a lot of spliced seeds. In addition, it was studied the effect of the different flow shapes of the stirred solution and the effect of the faults of growing faces of splicing seeds.
Halogen Form in Calcium Borate Glasses Containing Iron
Authors: Gohar I. A. , Megahed A. A. , Assem E. E.
Published: January 2007

Some halogen‐doped calcium borate glasses containing iron have been prepared according to the precentage molar composition [(30‐X)CaO · xCaX2 · 10 Fe2O3 · 60 B2O3)] and annealed. Scanning electron micrographs of heat‐treated glasses show that the microstructure consists essentially of two phases. By introducing the halogen ion one of the primary phases (Ca‐rich borate) decreases in its volume and a new phase appears and exists as crystalline form. A secondary phase can also be produced which segregates in Ca‐rich borate as droplets. Magnetic susceptibility, molar volume, and infrared measurements revealed that at concentrations of CaX2 < 10 mol% the halide ions may be introduced as modifiers and as network formers at CaX2 concentrations > 10 mol%.