bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoelastic and X‐ray topographic studies of residual stress and lattice deformation in GaAs single crystals
Authors: Adamkiewicz G. , Bajor A. , Wierzchowski W.
Published: January 2007

The GaAs crystals, grown with three different methods were simultaneously studied by means of photoelastic and X‐ray topographic methods. The methods provide complementary information about lattice deformation. The correspondence between interplanar distance changes and photoelastically measured stress values and the connection between cellular structure and high stress values were also found.
Multifrequency ultrasonic investigations in the liquid crystal 80CB
Authors: Venkatacharyulu P. , Gupta A. V. N. , Murthy V. Krishna , Rao J. V.
Published: January 2007

Investigations on the temperature variation of the specific volume and ultrasonic velocity (at four different fixed frequencies) in the liquid crystal 4′‐n‐octyloxy‐4‐cyanobiphenyl (80CB) are carried out both in the nematic and isotropic phases. From these studies various physical parameters like adiabatic compressibility (ßad), molar sound velocity or Rao number (Rn), molar compressibility (B), Van der Waal's constant (b) and the intermolecular free lengths (L) as a function of temperature are estimated. The variation of all these parameters with the ultrasonic frequency is also studied. The variation of the order parameter with temperature is also studied at the four frequencies and the results are discussed.
A special shear method of alignment for smectic liquid crystals
Authors: Jákli A. , Jánossy I. , Bata L. , Buka A.
Published: January 2007

A special shear method is presented for the planar alignment of smectic liquid crystals. The shear was applied at the isotropic‐smectic A or cholesteric‐smectic A phase transition temperature, when the “batonnets” floated freely in the isotropic or cholesteric fluid. This type of shearing provided good alignment in the broad range of sample thickness (up to 100 μm) with monodomain areas of about one square centimeter.
On the fivefold cluster symmetry
Authors: Kostov R. I. , Kostov I.
Published: January 2007

Seven pentagonal point groups are considered to be compatible with the local symmetry of crystal structures and important when interpreting the transition from precrystalline and quasicrystalline to true crystalline states. Clusters of fivefold symmetry seem to be stable balancing fourfold and sixfold symmetries. Together with clusters with other symmetry they play perhaps a significant role in the nucleation process and the ensuing growth of the crystals.
TEM studies of medium‐doses Kr+‐implanted silicon
Authors: Morawiec J.
Published: January 2007

〈100〉 silicon wafers implanted with 300 ke V Kr+ ions to the following 5 × 1013, 1 × 1014 and 5 × 1014 cm−2 doses were investigated by means of conventional and high voltage transmission electron microscopes. Planar‐view technique was applied to characterize primary damage and to determine the geometry and the nature of secondary defects left after the furnace annealing. It is concluded that implantation to the lowest and highest doses, respectively, leads to incomplete and complete amorphicity of entire bombarded region, whereas the intermediate dose forms a burried amorphous layer. Small interstitial Frank dislocation loops on {111} planes are the predominant secondary defects for the range of doses. Occurrence of additional rod‐like defects is related to the regions of discontinuous initial amorphicity.
Momentum distribution of electrons in metallic lithium
Authors: Mosharafa A. A. , Radwan A. M.
Published: January 2007

The momentum distribution of electrons in metallic lithium is calculated along the main axes of symmetry in momentum space. The crystal has a bcc structure of side 6.6317 a.u., both the crystal potential and orthogonalization to core states are adequately considered. The results show a marked anisotropy in the momentum distribution, this is mainly due to the strong effective potential seen by the conduction electrons. This causes states in the lowest band, particularly near the Brillouin zone boundary, to be strongly coupled.
Photoconductivity of ZnSe:Dy
Authors: Bhushan S. , Abraham K. E.
Published: January 2007

Nature of dark current has been investigated as a function of different metallic electrodes and the ambient temperature. Photoconductivity rise and decay curves have been investigated as a function of different metallic electrodes, flux and impurity concentrations, ambient temperature and the cell thickness. A maximum increase of 59 times in Ipc has been reported. Possible explanations are given for the observed effects.
On the crystallization of gypsum from supersaturated solutions
Authors: Hünger Klaus‐Jürgen , Henning Otto
Published: January 2007

The influence of supersaturation relations in the mixing of Ca2+‐ and SO containing solutions in different concentrations on the size and shape of growing gypsum crystals are investigated. The PBC vector method is used to describe the shape of gypsum crystals theoretically. The change of the specific electrical conductivity during the formation process is measured. The numerical integration of a differential equation system permits the relative determination of the nucleation and crystal growth rate. The value of the surface tension of gypsum nuclei is 3.3 · 10−3 N/m.

The formation of gypsum fibres is explained by the differences in the specific surface tension of some faces. The (hkl)‐ and (hk0) faces are unstable and grow faster than the (0kl) faces, that's why the a direction is the fibre axis. The prefered arrangement of CaSO4 molecules in a direction is supported through two fibrous crystals situated parallel a direction.
Reflectivity measurements of thin SiO2 layers in the soft‐X‐ray region
Authors: Klinkenberg E.‐D. , Illinsky P. P.
Published: January 2007

Energy and angular dependent reflectivity measurements of differently prepared SiO2 layers were made in the soft X‐ray region in order to study differences in their optical and electronic behaviour caused by the technological process. The optical constants of the layers were determined by fitting the angular dependent reflectivity data with a multilayer model which takes into account the roughness of all interfaces. Detailed knowledge of the polarization level of the primary beam from the synchrotron radiation source is needed for reliable results. The energy dependent reflectivity measurements indicate that high‐pressure dry‐oxidized layers have a more perfect structure than normal dry‐oxidized layers. Independent on the deposition process the SiSiO2 interface roughness amounts to ± 1 nm. The Si2p‐XANES of Si and SiO2 were detected.
The pseudomorphous phase transformation of faujasite‐type zeolites in processes of their crystal destruction
Authors: Richter‐Mendau J. , Lutz Wolfgang , Grossmann Andreas
Published: January 2007

The hydrothermal treatment of faujasite‐type zeolites in water, water vapour or weak acidic resp. alkaline solution usually leads to a pseudomorphous phase transformation. The process starts near the surface and penetrates the crystal. Due to the small reaction rate of the transformation as long‐time process the new material grows within the geometry of the dissolving zeolites. Therefore their crystal morphology is unchanged. The reaction mechanism of phase transformations is discussed.
Two step nucleation in glass‐forming systems
Authors: Kožíšek Z.
Published: January 2007

It is studied the effect of the preliminary heat treatment on the kinetics of nucleation by the numerical computation of the kinetic equations of the classical homogeneous nucleation theory for the model Li2O · 2SiO2 melt. It was shown, that we can obtain some unexpected results, e.g., the time dependence of the nucleation rate exhibits the jump depending on the preliminary heat treatment.
A method for determination of size‐dependent crystal growth kinetics from batch experiments (I). One‐experiment estimation
Authors: Blickle T. , Lakatos B. , Halász S. , Molnár I.
Published: January 2007

The method developed for determining size‐dependent crystal growth kinetics makes use of the assumption that the linear growth rate is a product of a size‐dependent factor and a supersaturation‐dependent one. The transformed form of the population balance equation, obtained by means of this assumption, is the basis of the evaluation utilizing measurement data from one seeded batch crystallization experiment, namely the size distributions of the seed and product crystals as well as the supersaturation course. The application of the method is illustrated by evaluating an experiment with potash alum crystals.
Gross dissolution of natural rhombohedral calcite crystal in nitric acid in dynamic etching condition
Authors: Mehta Bharat J. , Sidpara G. R.
Published: January 2007

Gross dissolution of natural rhombohedral calcite crystal in concentrated nitric acid in dynamic etching condition is studied and interesting results are obtained. The gross dissolution is maximum at 6 molar concentration of nitric acid in dynamic etching condition which is similar to static etching condition. The activation energy and pre‐exponential factor is calculated for different concentrations (range 3.0 to 7.5 molar) of nitric acid. The values of activation energy and pre‐exponential factors increase as concentration increases in dynamic etching, and it is more than static etching. The higher values of gross dissolution, activation energy, and pre‐exponential factor in dynamic etching condition is explained.
Equilibrium dopant incorporation in CVD silicon epitaxy
Authors: Kühne H. , Morgenstern Th.
Published: January 2007

In‐situ doping of epitaxial silicon layer with arsenic is controlled either by means of a mixed equilibrium – kinetical mechanism characterised by the influence of layer growth rate, or by means of a pure equilibrium‐related mechanism showing no layer growth rate effect. Layer growth rate can be selected to mark the transition from one mode to the other by introducing a characteristic rate v. Equilibrium controls dopant incorporation when vepi 〈 v 〉 0 is ture. That critical rate depends on temperatur as well as on input partial pressure of arsine and can be expressed by the three different empirical quantities A, B, and E. The former two of them are defined by conventional dopant incorporation theory. The additional quantity E is a function of arsine input pressure. That function not only defines an upper limit E= E∞ but also a lower limit E= 0 at which v= 0 is valid.
Comparison of lead solubility in NaCl crystals from data obtained by different methods
Authors: Dudnikova V. B. , Urusov V. S.
Published: January 2007

The solvus of the NaCl: Pb2+ system was found in the concentration range from 1.5 × 10−3 to 1.9 × 10−2 mol% at temperatures ranging from 375 to 430 °C from the data of flotation measurements of the crystal density. The heat of impurity dissolution equal to 2.0 ± ± 0.6 eV and the change in the vibrational entropy in the formation of the solid solution Sv/K= 20 ± 10 were determined.

Reasons for a difference in the estimates of lead solubility in NaCl, obtained from temperature dependences of light scattering and by other methods: measurement of the density, electric conductivity, and the electron‐microscopic decoration of the same crystals are discussed.
Ultra‐micro‐hardness measurements of non‐metallic crystals and an attempt for their calculation
Authors: Ulrich J. , Kruse M.
Published: January 2007

The ultra‐micro‐hardness of non metallic crystals has been measured for 16 substances. These are products usually produced in mass‐crystallization; inorganic, organic, with hydrates and unhydrates. The hardness‐force‐dependency was examined and data are compared to literature. KNO3 crystals showed a strong direction dependency (a factor of 2). In the end there has been made a first attempt to introduce a correlation of the measured micro‐hardness and physical properties of the crystals, but so far this was only possible for face centred cubic lattices.
Liquid crystalline phase transition studies in N(p‐n‐butoxybenzylidene) p‐n decylaniline, 40.10
Authors: Rao N. V. S. , Potukuchi D. M. , RaoA P. Bhaskara , Pisipati V. G. K. M.
Published: January 2007

The synthesis, characterization and the temperature dependence of density and ultrasonic velocity of N(p‐n‐Butoxybenzylidene) p‐n‐decylaniline, 40.10 are presented. The compound exhibits as trivariant liquid crystalline mesomorphism Viz., NAB the Isotropic – Nematic, and Smectic A – Smectic B phase transitions are found to be first order. However, the interesting Nematic Smectic A (NA) transition shows a second order nature. The NA transition results are discussed in the light of the available data on other nO.m compounds. The computed molecular parameters: adiabatic compressibility (βad) molar sound velocity (Rn) and molar compressibility (Aw) are presented.
Growth rate dispersion — a review
Authors: Ulrich J.
Published: January 2007

The growth rate dispersion (GRD) is reviewed from its start up to today. A definition is given followed by a summary of the facts and the first approaches for explanations. This all are surface reaction steps. The discussion of the consequences – no size dependent growth – is carried through. At the end the models (RF‐and CCG‐model) will be introduced which make it possible to work with the growth rate dispersion instead of size dependent growth. The newest approach is the superpositioning of the two models, this is perhaps the most promising way.
The current understanding of epitaxial CVD silicon layer doping in the light of modeling and theory development (VIII)
Authors: Kühne H. , Schröder K.‐W.
Published: January 2007

Lateral autodoping along the susceptor in downstream gas direction is described to be the result of a parasitic dopant partial pressure in the gas. Parasitic dopant species are distributed from buried layer surface into the gas during the predeposition period of the epitaxy process. They are diluted as well as gathered by the gas stream along the susceptor. The parasitic dopant pressure profile along the susceptor that exists when layer deposition begins, has been modelled by deriving an exponential expression taking into account a tilted flat susceptor having constant temperature, an increase of gas temperature along the susceptor, total gas throughput, total pressure, buried layer doping level, and the ratio of buried layer area per wafer to the susceptor area related to a wafer.
Cd diffusion in In0.53Ga0.47As
Authors: Ambrée P. , Gruska B.
Published: January 2007

Diffusion experiments of Cd in VPE‐In GaAs, lattice matched to InP, are reported. The closed ampoule technique used makes it possible to discuss the thermodynamics of the diffusion system consisting of the semiconductor samples, Cd3As2 as compound source and additional In or GaAs powder to prevent surface deterioration. Results on Cd concentration profiles, diffusion depth, carrier mobility and activation energy for Cd diffusion are given. The phenomenon of double diffusion fronts obtained in some experiments is discussed.
Temperature variation of the structural and thermal characteristics of YBa2Cu3O7−x in the range from 90 to 400 K
Authors: Olekhnovich N. M. , Zhabko T. E. , Orlova N. S. , Pashkovskii O. I. , Yanovich V. D. , Myaldun A. Z.
Published: January 2007

The X‐ray studies of the tetragonal YBa2Cu3O7−x compound are performed at different temperatures from 400 to 90 K and the temperature variation of the thermal expansion coefficients and the Debye characteristic temperature is determined. The anisotropy of thermal expansion is investigated. It is found that the two dynamical characteristics monotonously decrease with temperature lowering whereas for the superconducting orthorhombic modification their temperature dependences are anomalous. The mean thermal expansion coefficient as well as the overall Debye temperature for the tetragonal phase are smaller than those for the orthorhombic one.
Crystal and molecular structure of tetrachloro tetraaquo‐(1,8,10,17‐tetraazacyclooctadecane‐9,10‐dithione) dicopper (II)
Authors: Mishra Lallan , Pandey A. K.
Published: January 2007

Tetradentate bioactive macrocyclic thiourea 1,8,10,17‐tetraazacyclooctadecane‐9,18‐dithione(L) has been complexed with copper chloride dihydrate yielding bluish green coloured paramagnetic complex of orthorhombic geometry. The composition and tentative environment around Cu(II) is assigned on the basis of elemental analysis, IR, ESR spectra, X‐ray diffraction and magnetic studies.
Low temperature X‐ray diffraction study of CdI2 crystals
Authors: Wahab M. A. , Trigunayat G. C.
Published: January 2007

Solid state structural transformations in polytypic crystals of cadmium iodide have been investigated at low temperatures using X‐ray diffraction techniques. The crystals were cooled to liquid nitrogen and liquid helium temperatures employing three different methods. The results obtained are discussed on the basis of bond dissociation energies of interlayer and intralayer bonds and the possible mode of layer displacements in MX2‐type polytypic crystals.
On the growth kinetics of Y3Fe5O12: Bi films grown from Bi2O3PbOB2O3 melts
Authors: Durčok S. , Pollert E.
Published: January 2007

LPE isothermal growth of thin films of Y3−xBixFe5O12 from PbOB2O3Bi2O3 melts was used as a tool for studies of structure of high temperature solutions (HTS). Using an anionic model of HTS enthalpy and entropy of dissolving of the garnet phase, the equilibrium constant of Bi2O3 dissociation and diffusion coefficients of the growth unit were calculated from experimental data.
Structural aspects of thermal instability of polytypes in the CoC system
Authors: Rood' A. D. , Ustinov A. I. , Chuistov K. V.
Published: January 2007

The stability of the irregular long‐period structures being formed in CoC alloys during β → α transformation has been studied according to the carbon content. In the concentration range 0.2 to 1.2 at.% C the type of the short‐range order concerning the atomic layer stacking sequence remains unaffected on subsequent cooling of the alloy, whereas the α‐phase crystalline structure of the alloys with the carbon content of 1.3 to 2.17% C suffers polytype transformation. The transition from one polytype structure to another is found to be due to the decrease in length of the cubic‐type stacking sequences.
Dynamics of structural defects of LPE‐grown Gax‐In1−xP Layers
Authors: Popov A. , Dardjonov St. , Bahnev A. , Petrov Sr.
Published: January 2007

The structural properties of epitaxial GaxIn1−xP, LPE‐grown on 〈111〉‐oriented GaAs‐substrate, have been investigated. Two groups of samples have been distinguished with respect to the lattice parameters of the layers (a1) and the substrate (as): group A with a1 < as and Δa/as = (0.85 ÷ 2.98)%, and group B with a1 > as and Δa/as = (0.11 ÷ 1.98)%. Group A is characterized by a structure, including orthogonal, and slanted at 60° towards the surface, linear dislocations, originating from mismatch ones. Group B is characterized by a segmented‐surface structure. The optimum conditions for the growth of GaInP layers on GaAs substrates (initial temperature, saturation and composition of the melt, as well as cooling rate) are discussed on the basis of the data obtained.
Estimation of point defect parameters of solids on the basis of a defect formation model of melting (I)
Authors: Uvarov N. F. , Hairetdinov E. F. , Bollmann W.
Published: January 2007

It is proposed that the melting process is governed by the creation of lattice defects followed by a relaxation of the lattice in the vicinity of the defects. At the melting point Tm the mole fraction xL of defects within the melt is given by xL = L/ho (L heat of fusion; ho formation enthalpy of defects within the solid).
Estimation of point defect parameters of solids on the basis of a defect formation model of melting (II). Vacancy formation enthalpy in relation to the heat of fusion and the increase of volume due to melting
Authors: Bollmann W. , Uvarov N. F. , Hairetdinov E. F.
Published: January 2007

The mole fraction of vacancies within melts at their melting points is found to be xL = = 0.125 in the case of elements (with exception of inert gases), alkali halides, binary oxides and organic compounds. As to inert gases it is xL = 0.194. The formation enthalpy of vacancies (Schottky defects) is given by hS = L/xL (L heat of fusion) in every case. The increase of volume due to melting can be explained well by the vacancy model of melting: ΔV = VSxL (VS formation volume of Schottky defects).
Lattice parameter determination of superlattices
Authors: Berger H. , Rosner B. , Schikora D.
Published: January 2007

A method for determination of absolute lattice parameters of superlattices is described‐which does not use any relations to substrate reflections. For superlattices having tetragonal or trigonal symmetry, three parameters are to be determined. For this purpose, the diffraction angles of two reflections are measured, the third angle is obtained from the incidence angle difference of two single reflections of a “reflection group”. The peak shift caused by partial superposition of the single reflections, which occurs at larger superlattice periods, is corrected by means of simulation calculations. As an example, the results obtained on a PbTe/(Pb, Sn)Te superlattice are given and discussed.
Oxide‐free etching of (100) InP surfaces
Authors: Knauer A. , Hirsch D. , Staske R. , Zeimer U.
Published: January 2007

We report several combinations of chemical preparation procedures for selective cleaning of InP (100) surfaces in connection with storage procedures. A complex of analytical methods was used to get information about the surface state, the morphology, and the perfection of the surface. Using a standard etch procedure developed by KURTH et al. a post‐deoxidation by small concentrated HF or HNO3 is sufficient to get oxide‐free, clean InP (100) surfaces even after a storage in methanol for some hours.
Dielectric investigations on a binary system showing a “filled” SA Phase
Authors: Stettin H. , Kresse H.
Published: January 2007

A binary system of a double swallow‐tailed compound and a substance with a strong polar terminal group shows a pronounced induced SA phase. Investigations of the static dielectric anisotropy indicated a deviation from the simple mixing rule which was empirically introduced. We derived a better approximation taking into account the different molecular volumes of the substances. An unexpected increasing mobility of the strong polar molecules could be detected by relaxation measurements. This may be connected with a change in the short range order of the strong polar compound which is caused by the repulsive forces of the molecules.
The current understanding of epitaxial CVD silicon layer doping in the light of modeling and theory development (IX).Verification of the Multi‐wafer Autodoping Model
Authors: Kühne H. , Malze W. , Schröder K.‐W.
Published: January 2007

The multi‐wafer problem of lateral autodoping has been investigated in a rectangular, horizontally arranged epitaxy reactor by arranging on the top‐side As‐diffused source wafers and smaller high‐resistivity, p‐type sensor wafers which were for indicating lateral autodoping dose after a short‐lasting intrinsic layer deposition. Wafers were evaluated by sheet resistance measurements, IR‐determination of layer thickness and spreading resistance profiling. A linear increase of lateral autodoping dose along the susceptor has been proved and a linearly increasing parasitic dopant partial pressure deduced. These findings give evidence for the validity of the multi‐wafer model of lateral autodoping previously developed by the authors.
Study of the influence of additives on some parameters of batches for the synthesis of a light permeable polycrystal of yttrium oxide
Authors: Chomakov Iv. , Bogdanov B. I. , Petrov Sr. , Iliev J.
Published: January 2007

For obtaining light permeable ceramic of yttrium oxide, the initial batch should be highly sinterable. The influence of additives of ZrO2, ThO2, BeO, Gd2O3, Ga2O3, La2O3 and ThO2 + Nd2O3 on the particle‐size of the batch and the occurrence of defects in the unit cell of Y2O3 is studied. It has been found that the additives influence the particle‐size of the batch and increase the specific surface 4 times. The dependence of the unit cell parameter of Y2O3 on the ion radius of the additive is determined by means of X‐ray analysis. The measured density of sintered samples of the batches obtained is 99.9–99.96% of the X‐ray one and the light permeability at λ = 0.3–10 μm is from 60 to 92%.
VPE growth of InGaAS/InP structures using the hydride system
Authors: Diegner B. , Eberle T. , Jacobs K.
Published: January 2007

Some results on the VPE growth of InGaAs/InP structures in the hydride system using a single chamber horizontal reactor are described. The effect of partial pressures of the reactant gases and bypass‐HCl on epitaxial growth of InGaAs is discussed. The GaCl partial pressure was found to be the deciding growth parameter.
Formation of α‐Al2O3 by thermal decomposition of basic aluminium chlorides at low temperatures
Authors: Brand P. , Troschke R. , Weigelt H.
Published: January 2007

Basic aluminium chloride gels and the crystalline salt AlCl3 · 2 Al(OH)3 · 6 H2O are thermally decomposed to an amorphous product in a first step at low temperatures. If the reaction gas is rapidly removed the amorphous decomposition product directly transforms to corundum at increased temperature. Starting from gels the α‐Al2O3 formation begins at 420 °C, transformation of the crystalline salt at 530 °C. Structural similarities of precursor compounds and corundum are discussed as a reason for this behaviour. High contents of HCl and H2O in the atmosphere surrounding the specimen result in decomposition to transition aluminas at increasing temperature, which are transformed into α‐Al2O3 above 1000 °C.
Characteristic of the photoconductivity of thallium monoselenide
Authors: Hussein S. A. , Nagat A. T. , Mohamed N. M.
Published: January 2007

Systematic investigations on thallium monoselenide single crystal photoconductivity were reported at 300 K as a function of excitation intensity, side illumination, and wavelength. The samples were prepared using Bridgman technique. The photoconductivity as a function of the modulation frequency of the incident light was plotted at different values of light intensity. The effect of light intensity on the photocarrier lifetime was studied. The relation between the photocurrent and applied voltage at different values of light intensity was represented graphically. Side illumination effect in all these relations was checked. The spectral distribution of the photoconductivity of TlSe in the spectral region 1.24 ev to 1.77 ev was measured, and the energy gap was evaluated. All results were discussed and analyzed. Studies for such samples are very important and necessary in order to understand their use as photoconductor.
Study of calcium phosphate precipitation at 37 °C
Authors: Kibalczyc W.
Published: January 2007

The nature of the calcium phosphate formed when equal volumes of 20 mM CaCl2 and 15 mM or 12 mM K2HPO4 with pH 7.4 are rapidly mixed at 37 °C has been investigated by following the pH of the suspension as a function of time, by calorimetric and light scattering methods, chemical analysis and TEM. It is found that in the early stages of this process, there appears a spherular amorphous form of calcium phosphate, called ACP1, which transforms into a floccular amorphous form, called ACP2. We suggest that this transformation is solution‐mediated. ACP2 has not previously been clearly described as a separate phase and has not before been shown to be amorphous.
On the stereochemistry of 7‐[1(2‐carbomethoxyanilino)‐1‐(pyridyl)‐methyl]‐quinolin‐8‐ol (CMAP‐oxine)
Authors: Rericha A. , Seidel I. , Röbisch G.
Published: January 2007

C23H19N3O3, P1, a = 11,683(3), b = 7.740(2), c = 14.445(3) Å, α = 131.02(8), β = 95.43(8), γ = 95.02(8)°, Dx = 1.328 Mg · m−3, V = 0.9614 · 10−27 m3, Final R = 0.059 for 2905 symmetrically independent reflections (|F0| ≧ 3σ(F0)). The intensities were measured with an automatic diffractometer. There are two molecules in the unit cell. The substance is not tridentat in potentially coordination behaviour; coordination takes place (twodentat) on the oxine group.
A surface‐near stress resulting from Tamm's surface states
Authors: Gräfe W.
Published: January 2007

From the energy band approximation of KRONIG and PENNEY and TAMM'S model of surface states a contribution of the electrons localized at the surface to the surface tension of a solid has been deduced. The results illustrate the difference between the surface tension and the surface energy in the case of a solid. It has been explained how the above mentioned contribution to the surface tension is connected with the existence of a surplus surface‐near lokal stress.
Infrared optical characterization of epitaxial layer – substrate systems (II). Experimental results for AlxGa1−xAs/GaAS
Authors: Riede V. , Sobotta H. , Neumann H. , Gregora I. , Kamba S. , Vorliček V.
Published: January 2007

Infrared reflectance and transmittance spectra and Raman scattering spectra of the epitaxial layer‐substrate system AlxGa1−xAs/GaAs with compositions in the range x = = 0.08–0.49 are measured in the wavenumber range from 40 to 4000 cm−1. In analysing the spectra in terms of the respective theoretical relations for an optical two‐layer system the thickness of the layers, the optical mode characteristics and the free carrier parameters are determined. From a comparison with existing literature data for AlxGa1−xAs it is concluded that infrared optical measurements on epitaxial layer‐substrate systems can be successfully employed to evaluate the material parameters of epitaxial layers with thicknesses down to a few micrometers.
Characteristics of GaAsAlGaAs (SCH) lasers grown by low‐temperature LPE technique
Authors: Diaz P. , Prutskij T. A. , Sanchez M. , Larionov V. R. , Khvostikov V. P.
Published: January 2007

In this paper we report the performance and study of GaAsAlGaAs (SCH) laser. The structures were grown by a new variant of the LPE‐technique with temperatures regimes lower than 600 °C. The Low Temperature LPE‐technique, recently propoused by ANDREEV and coworkers at the IOFFE‐Physico‐Technical Institute exhibit growth rates of the growing layers as low as that corresponding to MBE or MOCVD techniques. In this way, it is possible to obtain and control layer thicknesses in the structure of the order of tens to hundreds of Ångströms. Laser heterostructures with active layer thickness of 30 nm, were performed and the lowest threshold current density of 437 A/cm2 for a cavity length of 1.33 mm were obtained. A typical growth process is described and a SEM structure microphotograph is shown. The dependences of the threshold current density Jth and the differential quantum efficiency ηd with the cavity length L are reported. From these data, other laser parameters are evaluated such as internal optical losses α1, internal quantum efficiency ηi and the dependence of the maximum of the gain factor against the nominal current density Jnom at threshold. This dependence was compared with the theoretical predictions and a good agreement was found.
On the morphological instability of the growing crystals (IV). The effect of supersaturation inhomogeneity upon the morphological stability of KDP single crystals
Authors: Staynova M. , Nanev Chr.
Published: January 2007

The diffusion‐induced inhomogeneity in the supersaturation on close packed faces of KDP crystals, growing from aqueous solutions has been investigated. The interferometrically found values of the concentration difference on the crystal edge and in the centre of the most closely packed face {100} were compared with the theoretically expected concentration nonhomogeneities calculated by means of CHERNOV's formula. The comparison has been performed especially for the moment when the KDP crystals lose the stability of their polyhedral shape and gradually acquire a skeletal form. A fairly good coincidence was found.
Mechanism of the oxygen‐stimulated deactivation of RuyTi1−y‐oxide overlayers on Ti studied by XPS, SEM and electrochemical techniques
Authors: Wagner N. , Kühnemund L.
Published: January 2007

By means of wet oxygen exposure the stability of RTO anodes has been observed. The deactivation is due to ruthenium loss via unstable higher surface oxides in a long time regime. As follows after uneffective subsurface annealing procedure the catalytic durability is reduced drastically by erosion stimulated increasing ruthenium loss of inhomogeneous active layer surfaces.
Ultrasonic relaxation studies in the liquid crystal 80CB
Authors: Venkatacharyulu P. , Gupta A. V. N. , Prasad N. V. L. N. , Rao J. V.
Published: January 2007

The variation of the ultrasonic velocity with temperature in the liquid crystal 4′‐n‐octyloxy‐4‐cyanobiphenyl (80CB) at four different fixed ultrasonic frequencies is studied. From these studies various relaxation parameters like the adiabatic relaxation time, velocity at zero frequency, in the vicinity of isotropic‐nematic phase transition and velocity at infinite frequency are estimated. From these parameters the relaxation mechanism in the vicinity of isotropic‐nematic phase transition is studied and the results are discussed.
The investigations on the synthesis of zeolite ZSM‐5 (I)
Authors: Wilkosz J. , Stobiecka E. , Dudek B.
Published: January 2007

The effect of the composition of reacting mixtures on the crystallinity of zeolite ZSM‐5 was investigated. The mixture of ethanol and ammonia was used as a templating agent. The quantitative determination of the phase composition of the obtained preparations was made on the ground of X‐ray diffraction. The ZSM‐5 zeolite of ab.90% phase purity, contaminated with mordenite, quartz and amorphous material, was obtained.
X‐ray diffraction studies of interdiffusion in InPGaP powder blends
Authors: Voland U. , Černý R. , Deus P. , Bergner D. , Fenninger G.
Published: January 2007

Interdiffusion in the InPGaP solid solution system is investigated by means of X‐ray diffraction of annealed powder blends. An activation energy of Q = (3.15 ± 0.3) eV for the interdiffusion process in the temperature interval 650… 725 °C was found. Diffusion parameters obtained by means of this method for InPGaP and InAsGaAs are discussed on the basis of lattice and atomic characteristics.
Macrosegregation of alumina in LiNbO3 single crystals
Authors: Erdei S. , Szaller Zs. , Raksányi K.
Published: January 2007

The macrosegregation of Al impurities has been studied in Czochralski grown LiNbO3 single crystals. Macrosegregation profiles determined by neutron activation analysis are presented and compared to predictions to the solutions of the neglect of parallel motion (NPM) model. A brief description of this model is given and a new formula is suggested for the interface segregation coefficient, k*, which accounts for different mechanisms of impurity incorporation due to the onset of criticalities. Optimization of model parameters led to fairly good agreement between observed and calculated profiles. Thus we have been able to give an upper estimate for the equilibrium distribution coefficient (k0) of Al. A numerical procedure was developed to assess the errors of the optimized model parameters.
Properties of some perovskites synthesized under pressure
Authors: Troyanchuk I. O. , Ges A. P. , Pastushonok S. N. , Pavlov V. I. , Balyko L. V. , Shipilo V. B.
Published: January 2007

Interstitial solid solutions with the perovskite – like structure were synthesized by solid phase reactions at high pressure and temperature. The synthesis conditions of single phased samples, their stability on heating in air were determined. The magnetic and electrical properties were measured.
Mass spectrometric analysis of gaseous crystallization medium, growing, and some properties of α‐Al218O3 crystals
Authors: Arzumanyan G. A. , Bagdasarov Kh. S. , Ryadnov S. N. , Garnikyan A. V.
Published: January 2007

Some gas phase processes during the vacuum vertical directed crystallization of α‐Al2 18O3 are studied in this paper. An effect of these processes on the H, C, N concentrations in the crystals is discussed. The detected pulsations of partial H2 and C18O pressures are a result of bubble destruction at the melt‐gas interface. The C18O bubbles are formed because of chemical interaction between the melt and carbon‐containing phases of container material. Besides the container wall, the H2 bubbles can be generated also at the crystallization front supersaturated by H2. The perfect α‐Al2O3 and α‐Al2 18O3 crystals grown under the same conditions have noticeable differences of their density, microhardness and lattice parameters. This is explained by an isotopic substitution effect.
Investigation of amorphous to crystalline transitions in InSe thin films
Authors: Rao S. Ramchandar , Nagabhooshanam M. , Babu V. Hari
Published: January 2007

The amorphous to crystalline transitions in InSe films have been investigated by different techniques. InSe compound was prepared from non‐stoichiometric amounts of indium and selenium in vacuum. The electrical conductivity and thermoelectric power measurements were made in films of different thicknesses and annealed for different times. TEP studies revealed that the films are p‐type. The conductivity studies have shown transition from amorphous to crystalline. The transition temperature is found to decrease with increase in (i) the thickness of the film, (ii) the time of annealing. Electronmicrographs and selected area diffraction patterns on as‐grown and annealed films have been taken and correlated with the conductivity results. The mechanism involved in the amorphous to crystalline transitions has been discussed.
Effect of pH on the electrical conductance of saturated aqueous solutions of KH2PO4 and its solubility
Authors: Sangwal K. , Olczyk E.
Published: January 2007

The specific conductivity of saturated aqueous solutions of KH2PO4 and its solubility are investigated in the pH range between 2.5 and 6.3. It is found that the values of specific conductivity and solubility show minima at pH of about 3.5 and 4, respectively. These observations are discussed in terms of the presence of a variety of species of different concentrations in saturated solutions of different pH. The conductivity data reveal that the solutions are highly associated. The presence of species other than H2PO4− and K+ explains the experimentally observed deterioration in the quality of KDP crystals from solutions of pH deviating from the natural value.
Microhardness of Hg1−xCdxTe and Hg1−xZnxTe
Authors: Fissel A. , Schenk M.
Published: January 2007

The microhardness of Hg1−xCdxTe and Hg1−xZnxTe has been measured on monocrystalline samples of Bridgman and THM crystals as a function of composition x by means of Vickers indentation measurements at room temperature. The curves show maxima of about 830 MPa at x ≈︁ 0.75 for Hg1−xCdxTe and of about 1700 MPa in the range 0.65 ≦ x ≦ 0.8 for Hg1−xZnxTe. The hardness‐relaxation behaviour has been measured on {111} samples in order to obtain the internal stress level and to investigate the stress‐relaxation behaviour. The theoretical hardening rate dH/d(x)0.5 was compared with experimental values.
Synthesis of AgIAgClCuI solid solutions for ice nucleation studies
Authors: Sivanesan S. , Gobinathan R.
Published: January 2007

Lattice parameter calculation and the nucleation temperature of AgIAgClCuI system are reported in this study. By vacuum fusion three samples of different molar compositions were prepared. The formation of the cubic solid solution of the above system was confirmed by X‐ray analysis. It is found that the 50:25:25 mole% composition of AgIAgClCuI has the highest nucleation temperature of −1.0 °C, which is far greater than −2.53 °C, −4.02 °C and −2.26 °C for pure AgI, AgCl, and CuI, respectively.
Questioning klinowski's concept of isomorphous substitution of silicon by aluminium in the framework of silicates
Authors: Lutz W. , Grossmann A. , Bülow M. , Gross Th.
Published: January 2007

Silicalite was treated in an alkaline solution of aluminate following Klinowski's instruction for ‘fine tuning’ of zeolitic catalysts. Instead of an isomorphous substitution of framework silicon by aluminium, a partial phase transformation of the silicate into an Al‐rich aluminosilicate gel was observed. A surface re‐alumination of residual crystals takes place.
Doping of PbTe and Pb1−xSnxTe with gallium and indium
Authors: Duguzhev Sh. M. , Makhin A. V. , Moshnikov V. A. , Shelykh A. I.
Published: January 2007

Precipitations in Indium and Gallium‐doped PbTe, SnTe and Pb1−xSnxTe are investigated. The compositions of the precipitated phases are PbGa6Te10 SnGa6Te10 and PbIn6Te10 for binary compounds. For Pb1−xSnxTe the precipitated phase composition corresponds to the continuous solid solutions Pb1−zSnzGa6Te10. Basic properties of the new compounds are determined. Their resistivity being of 5 ÷ 6 orders higher than that for Pb(Sn)Te, the anomalous transfer phenomena, observed in highly Ga(In)‐doped samples can be explained on the basis of the barrier model.
Theoretical approach to the mechanoluminescence excitation in solids
Authors: Chandra B. P. , Rahangdale Yuvraj
Published: January 2007

The present paper reports the results of some theoretical approach made to the studies of Mechanoluminescence (ML) of solids. It is found that the ML intensity depends on three major factors, the ML efficiency, damping factor, and elastic complience. It is concluded that the non‐viscous solids with high elastic compliance possessing luminescence centres with appropriate efficiency may exhibit intense ML. It is shown that the ML emission should take place only during the time at which there will be a change of applied pressure with time. There should be a phase difference between the applied pressure and the emitted ML signal.
Kinetic investigations within the transition region from polyhedral to skeletal growth mode (I). Growth kinetics of the basal face of zinc single crystals under diffusion conditions
Authors: Iwanov D.
Published: January 2007

The effect of diffusion in the vapour phase on the kinetics of growth of zinc single crystals in the presence of argon has been studied. The shift of the basal face in normal direction as a function of the time has been measured at constant temperature and supersaturation and argon pressures varying within the range 5–250 Torr as well as in vacuum 1 × 10−6 Torr. It has been established that the crystal size R changes with the time t following a linear and a parabolic law in the kinetic and the diffusion regimes, respectively. The kinetic critical size Rk for the transition from a kinetic to a diffusion regime has been experimentally obtained. A relatively good agreement is found between the experimentally established and theoretically calculated values of the critical size. The problems related to the transition of the basal faces of zinc single crystals from a kinetic to a diffusion growth mode is discussed.
The precipitation and hydrothermal crystallisation of alkaline‐earth. Metal aluminosilicate hydrates from aqueous solution: Crystalline phases and precipitation and recrystallisation mechanisms
Authors: Packter A.
Published: January 2007

The preparations, precipitations and recrystallisations of magnesium and calcium aluminosilicate hydrates, from aqueous suspensions of microcrystalline silica, aluminium hydroxide (and oxohydroxide) and magnesium (calcium) hydroxides at ambient temperatures to 400 °C, are surveyed. The phases reported in systems of different Mg(Ca)/(Al + Si) and Al/(Al + Si) composition ratios are tabulated and precipitation and recrystallisation mechanisms are proposed.
Geometrical properties of dislocations in potassium bichromate crystals
Authors: Szurgot M.
Published: January 2007

The geometry of growth dislocations present in potassium bichromate crystals grown from aqueous solution has been studied by etching. Etch topographs composed of dislocation etch grooves and grooves representing sector boundaries and growth bands have been analysed. It was found that most of the dislocation lines are straight and have well‐defined directions in each sector. Refractions of dislocations at growth sector boundaries and at other defects have been observed.
Thermal expansion of microcracks and grain boundaries in crystals (II). Thermal expansion and compression under pressure of intermicrocrystallite gaps in liquids
Authors: Vlasov A. D.
Published: January 2007

The changes of melting points under pressure (melting curves) in terms of the microcrystallite model of liquids has been studied. These curves allowed the estimation of temperature dependencies of the scale factor n (or effective temperature) for microcrystallite surfaces for a representative group of liquids above the melting points. Further, by using the results of the author's previous works, general temperature relationship of the scale factor n for microcracks and gaps over a wide range of bulk temperature has been plotted. This relationship is characterized by the sharp jump at the melting point and is asymmetrical with respect to the melting temperature line. Solid‐liquid transitions from the standpoint of the microcrystallite model have been discussed.
Kinetic investigations within the transition region from polyhedral to skeletal growth mode (IV). Comparison between the kinetic critical size and the observed morphological size of the basal face of zinc single crystals
Authors: Iwanov D.
Published: January 2007

The growth of zinc single crystals in a kinetic and a diffusion regime at argon pressures 5 – 250 Torr has been investigated. The growth of the edge of the basal face has been studied as a function of time at constant supersaturation and temperature of the furnace, simultaneously observing the surface of the {0001} face. It was established that in a kinetic growth mode the single crystals retained their polyhedral shape, whereas in a diffusion regime their form was changed into skeletal. A comparison was made between the critical size at which the transition from a kinetic to a diffusion regime began and the size at which a visible depression appeared on the {0001} face. In fact, the transition from a kinetic to a diffusion regime occurs simultaneously with the loss of the morphological stability of the basal face at kinetic critical sizes ak and Rk.
Crystal growth and dislocation arrangement of Czochralski alexandrite (BeAl2O4:Cr) single crystals
Authors: Qiang Zhang , Peizhen Deng , Fuxi Gan
Published: January 2007

The [001] oriented alexandrite (BeAl2O4:Cr) single crystals have been grown by the Czochralski pulling technique. The X‐ray topographic investigation indicates that the grown‐in dislocations mainly originate from the seed and propagate along the path normal or nearly perpendicular to the growth interface. The dislocation density and arrangement is closely related to the quality of the seed crystal.
Crystal structure of phenyl‐β‐methyl‐pyridyl hydroxyimide, C13H12N2O
Authors: Ahmed Farag I. S. , El‐Shora A. I. , Mostafa M. A. , Rybakov V. B.
Published: January 2007

Phenyl‐β‐methyl‐pyridyl hydroxyimide crystallizes in the form of prismatic crystals in the space group P 21 with Z = 4, a = 11.401(4) Å, b = 7.793(3) Å, c = 12.766(4) Å and β = 92.97°. The structure was solved by direct methods and was refined by block diagonal least squares calculation to a final value of 0.05. The pyridyl ring in molecule (II) is slightly distorted, all the other rings as expected are planar.