bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of decrease in supercooling on the growth rates: n‐Pentadecanoic acid
Authors: Prasad P. B. V.
Published: January 2007

The Growth rates of crystals fluctuate randomly. In view of such fluctuations, it is more appropriate if a statistical approach is adopted to describe the growth rates of crystals.
Infinite symmetry applied to crystals and crystal aggregates
Authors: Kostov R. I. , Kostov I.
Published: January 2007

Infinite symmetry is referred to for describing in a more rational manner the morphology of certain crystals and crystal, particularly mineral aggregates. Their non‐crystallographic forms depend on the peculiarities of their structure, enhanced growth along preferred directions and on the symmetry and composition of the growth environment. Apart from the seven Curie forms others, fitting the corresponding point groups are suitably added as variants of the growth geometry, applicable also to the property of matter.
EPR and pulsed NMR study of (NH4)2ZnBr4:Mn2+
Authors: Rao P. Madhusudana , Reddy K. V.
Published: January 2007

The EPR and pulsed NMR measurements of (NH4)2ZnBr4:Mn2+ have been carried out in the temperature range 110–473 K and 83–284 K, respectively. EPR spectra from three different paramagnetic entities have been observed. Intensity changes of certain lines in the EPR spectrum observed at ≈ 430 K indicate the occurrence of a phase transition. Another phase transition at ≈ 235 K is indicated as a change of slope in the T1 vs 1/T curve.
X‐ray powder diffraction investigations of solid solutions in the KClKBrH2O system at 298 K
Authors: Dejewska B. , Sȩdzimir A.
Published: January 2007

The measurements of crystal lattice parameters (a) of solid solutions being formed in the system KClKBrH2O at 298 K were conducted. The volumes (v) of unit cells and the densities (ϱ) of mixed crystals K(Cl, Br) were calculated. It was confirmed that in the investigated system continuous solid solutions were formed. The lattice parameters of these crystals formed from aqueous solutions of salts as well as from molten salts and also calculated by Durham‐Hawkins method were nearly identic.
A difference between initial growth stages of the AlGaAs/GaAs and GaAs/AlGaAs heterostructures produced by contact replacement of solutions
Authors: Bolkhovityanov Yu. B. , Logvinskii L. M. , Rudaya N. S.
Published: January 2007

The method of liquid epitaxial growth of GaAs/AlGaAs/GaAs heterostructures when the change of solutions occurs due to pushing off one melt by another is discussed. It has been shown theoretically and experimentally that the initial stages of film growth after the change of the binary GaAs melt on the ternary AlGaAs melt differ from that when the GaAs solution pushes off the AlGaAs liquid. The difference is caused by the inequality of the diffusion coefficients of As and Al in a multicomponent AlGaAs liquid (DAl > DAs). As a result, the growth of an AlGaAs film begins immediately in the case when the AlGaAs solution pushes off the GaAs liquid but in the opposite case the dissolution of an underlying AlGaAs solid is unavoidable and depends little on degree of a saturation of the GaAs washing solution. These peculiarities must be taken into account in discussions of abruptness and other properties of LPE‐grown AlGaAs/GaAs and GaAs/AlGaAs heterojunctions.
Electrical and infrared optical properties of CdIn2S4 single crystals grown by chemical transport
Authors: Neumann H. , Kissinger W. , Lévy F. , Sobotta H. , Riede V.
Published: January 2007

Single crystals of CdIn2S4 were grown by chemical transport with iodine as transporting agent using different transporter concentrations and temperature gradients. It is found that the electron concentration increases with increasing transporter concentration and decreases after annealing in a sulphur atmosphere. Infrared reflectivity and absorption spectra are measured at room temperature in the wavenumber range from 180 to 4000 cm−1 in order to determine the optical mode parameters of the compound and to evaluate the scattering mechanism of the electrons from the free carrier absorption. Lattice scattering is found to be predominant at room temperature for electron concentrations below about 4 · 1017 cm−3.
Effect of temperature gradient on the lamellar structure formation
Authors: Wołczyński Waldemar
Published: January 2007

The detailed definition of interplay between interface curvature and concentration field is presented. It explains an effect of horizontal component of temperature gradient on the lamellar structure formation during the steady‐state eutectic growth. This definition is composed of two competitive terms connected with the heat and matter transfers, respectively. The above competition is interpreted by using the thermodynamics of irreversible processes. Finally, it is shown that the lamellar spacing depends on both the growth rate and temperature gradient for a given regular eutectic solidifying under stationary conditions.

The proposed analysis is the fourth part of model developing in “Crystal Research and Technology” which is mentioned in the References.
X‐ray double crystal topographic measurements of distorted crystals
Authors: Trukhanov E. M. , Vassilev I. S. , Botev P. A. , Lyakh N. V. , Sidorov Yu. G. , Stenin S. I.
Published: January 2007

A procedure to measure local variations in lattice distortions based on the shrink and enlarge effect of contours, observed on topographs taken by X‐ray double crystal reflection technique has been proposed and applied in the study of CdTe crystals. A domination of the orientational component of distortions has been established, reaching to hundreds of arcsec for points at a distance of 1 cm. The variation in spacings Δd/d does not exceed hundredths of a per cent.
Long‐lifetime photoconductivity in Cz n‐ and p‐Si
Authors: Glinchuk K. D. , Litovchenko N. M. , Yu. Ptitsin V.
Published: January 2007

Long‐lifetime photoconductivity is observed in Czochralski‐grown oxygen‐rich heattreated n‐ and p‐type silicon crystals. It appears due to a slow electron (in Cz n‐Si) and hole (in Cz p‐Si) recombination via two kinds of oxygen‐induced recombination centres. Dependences of the long‐lifetime photoconductivity on the oxygen content, excitation intensity and temperature are presented. Possible models to explain an appearance of the long‐lifetime photoconductivity in Cz n‐ and p‐Si are discussed. The data presented are important for understanding the long‐time photoeffects in semiconductors and for elucidating the origin and structure of oxygen‐induced recombination centres in silicon.
Solid inclusions in man‐made quartz crystals (I) microscopic investigations
Authors: Kirov G. K.
Published: January 2007

Microscopic study of a number of commercial and laboratory quartz crystals grown from Na‐alkaline solutions at about 350 °C show that they always contain fluid and solid inclusions. More than 99% of the inclusions in normally grown crystals occur at the seed plate or very close to it, not further than 0.2–0.5 mm. The solid inclusions occur as single particles, in small groups or in clusters and aggregates containing hundreds of various inclusions. Dimensions of single particles vary from 1 to n · 10 μm but separate inclusions and especially aggregates can measure n · 100 μm. Normally, the number of solid inclusions is of the order of n · 100 per cm2 but in separate “patches” measuring up to several cm2 the density reaches to n · 1000 per cm2. Regardless of the origin of the host crystal, the solid inclusions are always of three kinds: 1. Quartz microcrystals — husks, whiskers, needles, and elongated plates which comprise up to 30% of all inclusions; 2. Several still unidentified non‐quartz phases, tentatively designated as “silicates” — euhedral and anhedral crystals with its refractive index greater than the index of quartz, and fine or submicroscopic elongated crystals of low index, which amount to 70%; 3. Technogene impurities consisting of small irregular opaque particles of metal oxides and presumably graphite which occur only sporadically. The formation of solid inclusions depends probably much more on the surface tension than on mere precipitation.
Analytical theory for flexo‐electric domains in nematic layers
Authors: Schiller P. , Pelzl G. , Demus D.
Published: January 2007

An analytical theory for flexo‐electric domains in planar nematic films with positive dielectric anisotropy is proposed. It can be decided by a simple criterion, whether flexoelectric domains or the ordinary Fredericksz transition will occur.
Induced SA phases and reentrant nematic phases in binary systems of homologous terminal‐nonpolar compounds
Authors: Pelzl G. , Szabon J. , Wiegeleben A. , Diele S. , Weissflog W. , Demus D.
Published: January 2007

The isobaric phase diagrams of binary systems are presented in which one component is represented by members of the homologous series of swallow tailed compounds. The occurrence of induced SA phases and reentrant nematic phases was studied in dependence on the length of the alkyl chain of the swallow tailed compound. In some selected binary systems X‐ray investigations and calorimetric measurements were performed. An attempt has been made to interprete the results by a simple packing model.
Supersaturation by gelling: Gel‐grown single crystals of metal(II)carboxylates
Authors: Lentz A. , Fetzer Th. , Voitenleitner I. , Hauber Th. , Abou‐El‐Wafa O.
Published: January 2007

Hydrolysis and polycondensation of tetraalcoxysilanes create both: a crystal growth medium and an alcohol‐water mixture with diminished solubility for a lot of compounds. Solvent varying gel crystallization is shown for twenty metal(II)carboxylates in TMOS. The influence of pH‐value, salt‐ and TMOS concentration and combination of this method with cooling crystallization are described.
Crystal and molecular structure of 1‐diazo‐2,3,4,5‐tetraphenylcyclopentadiene
Authors: Ramm M. , Schulz B. , Thurner J.‐U. , Tomaschewski G.
Published: January 2007

Mr = 396.30, monoclinic space group P 21/c, a = 10.145(2), b = 18.523(4), c = 12.443(2) Å, β = 110.31(2)°, V = 2193(1) Å3, Z = 4, Dx = 1.201 Mg m−3, F(000) = 832, λ(MoKα) = 0.71069 Å, μ = 0.7 mm−1. The crystal structure was determined by direct methods and refined by least‐squares procedure to the discrepancy factor R = 0.039.
Cr doping influence in ZnS single crystals on the complex disordered polytypical structure
Authors: Gosk J. , Kozielski M. J.
Published: January 2007

The results of X‐ray investigation of real structures of ZnS:Cr single crystals are presented. Doped ZnS single crystals were grown from the melt by Bridgman's high pressure method. Cr dopant converts the structure of ZnS crystals from 3C with individual stacking faults (for pure ZnS) to the complex polytypical structures disordered along one dimension and including specific orderings of cp layers that form polytype cells LH (L = 2l, l = 2, 3, 4 and 5). The structures are characterised by Farkas‐Jahnkes statistical parameters π(m, p) and by parameters PLH of the polytype unit cell formation probability (Kozielski, Tomaszewicz 1986; Palosz, Przedmojski).
ΔE‐effect in CoZn ferrites
Authors: Murthy S. R.
Published: January 2007

A study of the dependence of the elastic behaviour of polycrystalline mixed cobalt‐zinc ferrites on magnetic field (ΔE‐effect) and temparature has been made using an ultrasonic method. The observed ΔE‐effect in the case of cobalt zinc ferrites has been interpreted in terms of two domain processes.
Growth of octacalcium phosphate and dicalcium phosphate dihydrate crystals in silica gels
Authors: Sokołowski T. , Wiktorowska B.
Published: January 2007

The crystallization of octacalcium phosphate (OCP) and dicalcium phosphate dihydrate (DCPD) have been studied at ambient temperature in silica gel using double diffusion system. The first stage of evolution of the OCP spherulites as well as their growth have been observed by optical microscopy. The growth rate of the OCP spherulites under stable external conditions was constant. The formation of DCPD crystals has been observed in the last stages of experiments.
Crystal and molecular structure of 17α,21‐dihydroxy‐1,4‐pregnadiene‐3,20‐dione
Authors: Scharfenberg‐Pfeiffer D. , Megges R. , Höhne E. , Stopsack H.
Published: January 2007

The title compound 17α,21‐dihydroxy‐1,4‐pregnadiene‐3,20‐dione crystallizes in the orthorhombic space group P 212121 with four molecules in the unit cell and the lattice parameters a = 7.727, b = 10.095, c = 22.876 Å. The crystal structure was determined by direct methods and refined by full matrix least squares calculations up to the discrepancy factor R = 0.048.
Simulated diffraction on TiN coatings with gradients
Authors: Valvoda V. , Rafaja D. , Černý R. , Kužel R.
Published: January 2007

A method of computer simulated X‐ray diffraction patterns has been applied to TiN coatings assuming different gradients of lattice parameters, microstrain or grain size in the direction normal to the substrate surface. The generated diffraction patterns have been compared with experimental ones and a possibility of real occurrence of such gradients is discussed. This method is superior to the methods based on intensity weighted average quantities which do not take into account actual profiles of diffraction peaks.
Infrared lattice vibration study of CuIn5S8
Authors: Neumann H. , Sobotta H. , Riede V. , Tezlevan V. E. , Syrbu N. N.
Published: January 2007

Infrared reflectivity spectra of the spinel compound CuIn5S8 are measured at room temperature in the wavenumber range from 180 to 4000 cm−1. It is found that the spectra are dominated by two strong modes with frequencies and oscillator strengths that are practically equal to those of the corresponding modes in the normal spinels of type AIIIn2S4. A very weak additional mode at 357 cm−1 is ascribed to a secondary tetragonal phase previously observed in as‐grown CuIn5S8 single crystals.
Dielectric investigations of a binary system with strong correlation of the molecules
Authors: Kresse H. , Heinemann S. , Hauser A. , Weissflog W.
Published: January 2007

Dielectric measurements on oriented liquid crystalline substances in the frequency range from 10 Hz to 100 kHz have been carried out. The static dielectric constant parallel to the director of both single components shows a strong decrease in relation to the expected value. In the case of the swallow‐tailed compound this effect can be described by assuming an equilibrium between statistically and antiparallel oriented molecules. The second component has an extremly strong tendency to be antiparallel oriented. In the mixture of both a continuous change of the correlation was observed.
Crystal growth and physical properties of monoclinic L‐arginine hydrochloride monohydrate, C6H14O2N4HCl · H2O, and L‐arginine hydrobromide monohydrate, C6H14O2N4HBr · H2O
Authors: Haussühl S. , Chrosch J. , Gnanam F. , Fiorentini E. , Recker K. , Wallrafen F.
Published: January 2007

Single crystals of optical quality of L‐arginine HCl · H2O and L‐arginine HBr · H2O with dimensions up to 80 × 60 × 30 mm have been grown from aqueous solutions by controlled evaporation at about 310 K. The isotypic crystals exhibit a quite similar behaviour with respect to morphological, pyroelectric, dielectric, optical, thermal expansion, electrostrictive, electrooptic, elastic, thermoelastic and non‐linear optical properties. A distinct anisotropy of the longitudinal elastic stiffness is observed with a maximum along the direction of the alignment of the arginine ions. Nearly in the same direction a minimum of thermal expansion, dielectric constant and index of refraction is found. The pyroelectric, electrostrictive, electrooptic and non‐linear‐optical effects are of only mediocre magnitude except the electrostrictive constant d211 which surmounts the longitudinal electrostrictive constant d111 of alpha‐quartz by a factor three.
Observation of the boundary layer on the top of ice growing from melt
Authors: Krasinski M. J. , Michalski D. , Karniewicz J.
Published: January 2007

The boundary layer appearing near the ice front during directional freezing of water was investigated by the Mach‐Zehnder interferometer. Temperature profiles in the cell during experiments were displayed. Properties of this layer were measured in dependence on growth rate and properties of water. The gas bubbles capturing and building of air channels in the ice were also observed. Nature of the observed transition layer is briefly discussed.
LPE growth and characterization of InP/InGaAsP ridge‐waveguide lasers at 1.3 μm‐wavelength
Authors: Gottschalch V. , Rheinländer B. , Oelgart G. , Brühl H.‐G. , Bayer W. , Schwarz G. , Vogel K.
Published: January 2007

This paper presents the fabrication and the lasing characteristics of 1.3 μm‐wavelength ridge‐waveguide laser. The epitaxial material used in this study was grown applying the step‐cooling technique of liquid phase epitaxy (LPE). The growth conditions for InGaAsP layers lattice‐matched to the (001) InP‐substrate are reported for lattice compositions corresponding to photoluminescence peak wavelengths of 1.07, 1.14, and 1.31 μm. We have used a conventional multiple‐bin sliding boat to grow the LPE layers and a second apparatus for achieving batches of melts of uniform compositions. In the LPE apparatus the various batch melts (In–Sn In–Zn; In–Ga–As of different composition) were saturated with phosphorus using the seed dissolution technique. The epitaxial layers were grown by a single phase technique at a constant temperature. This LPE growth technique is useful for the fabrication of double‐heterostructure wafers with an uniform alloy composition and a well‐defined layer thickness.

Using these epitaxial materials, metal‐clad ridge‐waveguide (MCRW) lasers have been prepared with stripe widths of 3.5 μm. CW threshold currents of 18 mA at room temperature are achieved for 200 μm long cavities. These lasers have T0 values ranging from 50 to 70 K and well linear L‐I‐characteristics.
Some correlations in liquid phase growth (I)
Authors: Peev N. S.
Published: January 2007

In this work we consider some circumstances of the growth process of an n‐component solid phase from an n‐component liquid phase and provide some general relationships, which must be observed in this growth process. In more detail we treat the two extreme cases: growth when (∂C/∂t = 0) — the stationary case; growth when (∂C/∂x = 0) — no concentration gradients in the liquid phase. In our opinion these theoretical considerations will simplify the investigations of multicomponent systems.
Comparative infrared lattice vibration study of LiGaO2 and LiInO2 (II). Interatomic force constants
Authors: Neumann H.
Published: January 2007

The frequencies of the wurtzite‐like modes due to Li–O and Ga–O bond vibrations in LiGaO2 and of the rocksalt‐like mode due to Li–O bond vibrations in LiInO2 are determined from the infrared reflectivity spectra of the compounds. The force constants for the Li–O and Ga–O bonds in LiGaO2 follow the same trends as those found for the AIBIIIC2VI chalcogenides with tetrahedral cordination. The results for LiInO2 are compared with measurements on the octahedrally coordinated modification of LiAlO2.
On chemical kinetics of silicon deposition from silane (I). The first order chemical reaction
Authors: Kühne H.
Published: January 2007

Theoretical expressions for silicon layer deposition in consequence of silane decomposition within an open isothermal reaction tube has been derived for the case of homogeneous as well as heterogeneous gas reaction. Layer growth distribution along reaction tube axis has been taken into consideration as well as average layer growth rate related to silane consumption during its passage through the tube on the one hand and to growth rate distribution along the tube on the other. Comparing the theoretical results with experimentally based data homogeneous rather than heterogeneous reaction mode might be preferred. In consequence, however, layer growth rate should be linearly effected by the ratio of reactor gas volume to total substrate surface area. In a practical sense average growth rate, and so axial growth homogeneity, should be expected the higher the lower silane consumption efficiency would be adjusted.
The influence of small deviations from stoichiometry on the properties of YBaCuO superconductor ceramics
Authors: Matz W. , Rudolph K. , Anwand W. , Opitz R.
Published: January 2007

According to a central composite design samples with deviations from stoichiometry YBa2Cu3O7−x of ±2.5 wt% in the ingredients were prepared. The influence of these deviations on phase content, superconducting properties and microstructure of the ceramics was studied.
Electrolytic growth and dielectric properties of magnesium hydrogen phosphate single crystals
Authors: Desai C. C. , Shukla M. J.
Published: January 2007

The growth of MgHPO4, magnesium hydrogen phosphate, (MHP) single crystals in silica gels under the influence of an externally applied uniform electric field is described. A controlled reaction between magnesium chloride and orthophosphoric acid by a diffusion process in the gel medium is employed. The bright, transparent MHP crystals upto 4 × 2 × 1 mm3 in sizes are grown at room temperature. The dielectric measurements are carried out in the temperature range between 300 to 650 K. The effect of the applied frequency on the dielectric constants and the dielectric losses are investigated. It is observed that the mechanism of the dielectric behaviour is different in the lower and higher frequency and temperature ranges. The activation energy of the oscillators are calculated and found to be 1.105 eV. Attempt is made to draw some qualitative conclusions, taking in view the existing theories of various kinds of polarization, and implications are discussed.
On chemical kinetics of silicon deposition from silane (III). LPCVD poly silicon formation in the temperature range 900–950 K
Authors: Kühne H. , Harnisch H. , Puk P. , Lassan B.
Published: January 2007

LPCVD poly Silicon deposition form silane has been investigated for limited conditions regarding temperature, silane input and pumping speed. It has been found that layer growth is controlled by a chemical reaction of 0.5th‐order in consequence of which growth rate linearly decays along the axis of an open isothermal reactor tube. The slope of that decay is determined not only by the reaction rate constant but also by linear gas velocity within the tube and that part of total substrate surface area that is effectively exposed to silane at each wafer position. In conseqence growth rate decay is the steeper not only the higher temperature will be chosen but also the slower gas velocity is adjusted and the smaller wafers are separated to each other. The kind of how axial layer growth rate distribution is effected by changing wafer spacing is a proof for the heterogeneous reaction mechanism. The silicon forming reaction is characterised by an activation energy of about 52 kcal/mole.
Study of ZnSe and CdSe thin film epitaxy on germanium and silicon substrates
Authors: Bruk L. I. , Kabir S. M. , Korotkov V. A. , Leondar V. V. , Simashkevich A. V. , Tsaran V. M.
Published: January 2007

The parameters of vaporization, mass‐transfer, condensation, and epitaxial growth by hot wall technique (HWT) of ZnSe and CdSe thin films on monocrystalline Ge and Si substrates are studied (Bubnov et al.). It is shown, that the layers structure is improved as the mass transfer mechanism approaches to gasodinamical vapor flow.

The influence of condensation temperature of the layers on their crystallographic structure is shown. The increase of the temperature gradient from the source towards the substrate as well as the substrate temperature conditions for growing layers of hexagonal modification. The decrease of the temperature gradient leads to cubic modification. The electron diffraction study revealed the stepwise character of the zinc selenide and cadmium selenide film growth.

The knowledge of the parameters of ZnSe and CdSe thin films on monocrystalline Ge and Si by hot wall technique at relatively low substrate temperatures allows to obtain layers, suitable for formation of solid state devices for registration and reflection of optical information.
Coefficient of volume expansion and thermoacoustic parameters in N‐(P‐hexyloxybenzylidene)‐P‐toluidine
Authors: Sivaram C. , Rao J. V. , Venkatacharyulu P.
Published: January 2007

The Sharma constant So, the isochoric temperature coefficient of volume expansivity, the isochoric temperature coefficient of internal pressure, the reduced compressibility, the reduced volume and a few other acoustic parameters are evaluated for N‐(P‐Hexyloxybenzylidene)‐P‐Toluidine (HBT) using only the coefficient of volume expansion. The Sharma constant which was shown by Sharma to be a constant in a number of non‐mesomorphic systems is bound to be a constant in the liquid crystal HBT also, investigated by the authors with the same character constant value both in the isotropic and nematic phases with anomalous behaviour and pretransitional effects at and in the immediate vicinity of the isotropic‐nematic phase transition temperature. The various other acoustic parameters estimated for liquid crystal HBT investigated in the present studies are compared and discussed with the values reported by Sharma, and by Sharma and Reddy for certain other non‐mesomorphic systems.
X‐ray characterization of CdTe crystals with natural faces
Authors: Auleytner J. , Majewski J. , Furmanik Z. , Golacki Z.
Published: January 2007

The exact characterization of natural crystal faces is very important from the point of view of the proper conditions of crystal growth and of the choice of an appropriate substrate for obtaining epitaxial layers. In this work various X‐ray diffraction methods were used to obtain the maximum information about the CdTe crystal surface structure. Applied X‐ray techniques allowed to detect the number of defects even on the natural mirror‐like faces of the crystal which can be treated as a seemingly perfect one.
Characterization of Nickel and Tungsten species supported on alumina
Authors: Sarbak Z.
Published: January 2007

The effect of thermal activation on NiW/Al2O3 catalyst in their oxide, reduced and sulfided forms has been studied by X‐ray diffraction (XRD), differential thermal analysis (DTA), diffusion reflectance spectroscopy (DTS), infrared spectroscopy (IR), Raman spectroscopy (RS), electron paramagnetic resonance (EPR) and magnetic susceptibility measurements.

Thermal activation in oxygen results in production of many species of the mono‐, di‐, and polymeric type. Upon activation in hydrogen they are partially reduced, whereas upon sulfiding number of oxide ions are replaced by sulfide ones. Among others, formation of dithiotungstenates was proved, yet neither the exchange of hydroxyl groups for the thiol ones nor the exchange of bridge oxide ions for sulphur ions was indicated.

The simultanous reduction and sulfiding process do not affect the spinel subsurface structure. With respect to the surface species, the catalyst's support takes on a stabilizing function.
Crystal and molecular structure of 7‐[1‐(2‐carbomethoxyanilino)‐1‐(phenyl)‐methyl]‐quinolin‐8‐ol(CMAB‐Oxine) and comparising consideration to CMAP‐Oxine
Authors: Rericha A. , Seidel I. , Röbisch G.
Published: January 2007

C24H20N2O3, Pbc21, a = 11.338(4), b = 7.786(3), c = 44.381(6) Å, Dx = 1.29 Mg · m−3, V = 3.82053 · 10−27 m3. There are eight molecules in the unit cell (two molecules, A and B, in the asymmetric unit). The substitution of N (CMAP‐Oxine) by CH(CMAB‐Oxine) in the aldehyde participant of reactants creates differences both in intermolecular contacts and orientation phenomenons of ring planes. A high degree of selectivity of the substitution position for both compounds is given. The reactions to the synthesis of both compounds are difficult to agree upon with the characteristic feature of the Mannichreaction and corresponded more to the character of the electrophilic substitution of aromatics.
Influence of the model parameters on the Monte Carlo simulation of the initial aggregation of point defects in solids
Authors: Schmidt R. , Berg G.
Published: January 2007

The kinetic process to reach the equilibrium state of lattice defects is characterized by an aggregation of these defects. The formation of the precursors of the aggregates, the so called critical nuclei, can be investigated by Monte Carlo simulation. But in many cases the exact interaction potential between the movable defects in the lattice and the nucleus is unknown. Therefore such simulations were carried out for different typical interaction parameters. Conclusions concerning the general behaviour were derived. The calculations allow especially an estimation of the influence of strength of the potential and temperature on the number of defects forming a critical nucleus.
On chemical kinetics of silicon deposition from silane (IV). In‐situ phosphorus doping of LPCVD poly silicon in the temperature range 900–950 K
Authors: Kühne H. , Harnisch H. , Nüske G.
Published: January 2007

Highly in‐situ phosphorus‐doped LPCVD poly silicon deposition from mixtures consisting of silane and phosphine has been investigated for limited conditions regarding temperature, silane input, phosphine‐silane ratio and total pressure. Agreeing with the deposition of undoped poly silicon, growth rate linearly decays along the axis of the wafer cage applied for in‐situ doped poly silicon. In consequence layer growth should be controlled by a chemical reaction of 0.5th order. In contrast to undoped poly silicon the slope of axial growth rate decay increases with the distance between wafers increased. This behaviour is a proof for a homogneous chemical reaction mechanism. The silicon forming reaction is characterized by an activation energy of about 25 kcal/mole for PH3/SiH4 = 0.003.
Application of various modes on the growth of magnetoplumbite single crystals from the Na2OBaO flux
Authors: Pollert E. , Durčok S. , Matějková L. , Nevřiva M.
Published: January 2007

Several growing modes including the bottom growth, the growth on a thermocouple ball and the top seeded growth, were tested to grow BaFe12−2xMgxTixO19 and BaFe12−xGaxO19 magnetoplumbite single crystals from the Na2OBaO flux. Disadvantages of the bottom growth, inhomogeneities, inclusions, difficult separation of the crystals were restricted by using of the top‐seeded growth and by optimization of the ACRT program.
Influence of crystallisation conditions on the microtexture of the directionally solidified eutectic of the MgF2CaF2 system
Authors: Barta Č. , Fendrych F. , Recker K. , Tříska A. , Wallrafen F.
Published: January 2007

The influence of high‐frequency (HF) and resistive (R) heating of a vertical crystallizer furnace on the directional solidification process of the MgF2CaF2 system eutectic has been compared. The turbulent flow induced by HF heating given rise to inhomogeneities in microtexture, which do not occur under R heating conditions. Variations in the growth rate (v) and temperature gradient (ΔT) lead to characteristic changes of the eutectic microstructure: from lamellar to rod‐like. Quantitative analysis of these changes was advantageously performed using a digital image analysis of the area (AR), maximum cross‐section (D‐MAX), direction of the maximum cross‐section (ANGLE D‐MAX) of MgF2 particles of the microtexture. This was recorded on SCAN images of transverse cuts through the given directionally solified samples as well as the analysis of the shape of MgF2 particles.
Role of physical factors in solid – liquid interface formation during oriented eutectic growth
Authors: Wolczyński Waldemar
Published: January 2007

The basic physical factors affecting the eutectic interface shape observed in the microscopic scale have been discussed regarding the theory of completely coupled growth. The analysis considers phenomena like: heterogeneous nucleation and growth, interface undercooling of the both eutectic phases, phase protrusion and eventually horizontal temperature gradient. The contribution of the transition layer to the interface shape formation is emphasised.
To the non‐dislocation model of crystal tensile strength
Authors: Vlasov A. D.
Published: January 2007

The non‐dislocation model of crystal planes slipage has been proposed. The slipage of two planes begins when these planes have diverged to the critical distance by influence of the thermal stress σth that had to be appeared owing to heating of these planes above bulk temperature. This heating is due to the phenomenon supposed by the author, called the effective temperature of crystal surfaces. In such a way the simple expression for load/microscopic strain relation has been proposed. The calculated ratio: tensile strength/Young's modulus (6 · 10−3) is in good agreement with experimental data (of 1 to 2 · 10−3) for a number of metals. The common theories on tensile strength do not take into account the above mentioned thermal stress and this is the reason for theoretical data on strength being of three orders of magnitude above the experimental values.
Influence of O2 in photoluminescence measurements in Zn‐doped Al0.56Ga0.44as layers
Authors: Gracia M. , Hernández L. , Purón E. , De Roux S.
Published: January 2007

We have studied by photoluminescence measurements the influence of O2 in the broad band in Zn‐doped‐Al0.56Ga0.44As grown by LPE technique. The emission peak energy of the band shifts monotonically with temperature. The dependance of the halfwidth with temperature fits the configuration coordinate model. We suggest a ZnGaO2 complex center is responsible for the band. We have determined the ionization energy of Zn and O2.
Temperature Measurement in a THM Solution Zone for the Growth of Hg1−xCdxTe
Authors: Kiessling F. M. , Gille P.
Published: January 2007

A combined process for temperature measurements in THM growth systems is described including the preparation of the source material as well as the liquid solution zone in one and the same ampoule. Using starting compositions with an excess of that component to act as the solvent the solution zone is formed during the travelling heater procedure. With thermocouples attached to the slightly modified ampoule axial temperature distributions were recorded under the usual THM growth conditions. The measurements were done in Hg0.8Cd0.2Te growing from Te‐rich solution zones. The procedure described can be applied to all materials for which THM crystal growth can be achieved.
Observations of crack patterns in NaSbF4 and NaSb2F7 single crystals
Authors: Benet Charles J. , Gnanam F. D.
Published: January 2007

Crack pattern studies on NaSbF4 and NaSb2F7 single crystals have been carried out using Leitz Wetzler microhardness tester. Attempts have been made to understand the nature of the cracks developed around the microindentation impression. The fracture toughness, index of brittleness and crack resistance have also been calculated.
Growth Velocities and Disappearance of Faces of Crystals
Authors: Szurgot M. , Prywer J.
Published: January 2007

The formulae for critical absolute and relative growth velocities which govern the disappearance of faces have been derived and discussed. A face can disappear in the habit only if its velocity is greater than the critical one. Both the fast‐ and the slow‐growing faces can disappear. It was shown that BORGSTRÖM's formula describes only a special case of disappearance of faces. Apart from the nearest neighbours also those farther ones influence the size and presence of faces. The calculations have been verified by the experimental results for triclinic potassium bichromate (KBC) crystals.
Crystal Growth of 2‐Cyclooctylamino‐5‐Nitropyridine (COANP) and 2‐(N‐(L)‐Prolinol‐5‐Nitropyridine (PNP) from TMS Gels
Authors: Br̆ezina B. , Hulliger J.
Published: January 2007

Single crystals of 2‐cyclooctylamino‐5‐nitropyridine (COANP) and 2‐(N‐(L)‐prolinol‐5‐nitropyridine (PNP) were grown from tetramethoxysilane gels. Lowering the temperature or seeding of supersaturated water/ethanol gel solutions led to optical quality crystals of several mm in size. In the case of PNP the addition of Nd3+ to the gel solutions decreased the concentration of milky defects. Morphological descriptions for COANP and PNP crystals are given.
On the Synthesis and Characterization of Zeolite ZSM‐20
Authors: Tuan Vu Anh , Fricke R. , Szulzewsky K. , Kosslick H.
Published: January 2007

ZSM‐20 is a silicon‐rich analog of the faujasite‐structure, the synthesis of which is complicated. Starting from known synthesis recipes its crystallization in the system Na2O · Al2O3 · SiO2 · H2O is investigated in the presence of tetraethylammoniumhydroxyde as templating agent. The aim was to find the critical conditions for its synthesis. The synthesis products obtained are investigated by X‐ray diffraction, thermal analysis and i.r. spectroscopy.
Formation of Concave‐Convex Interface Shape during Oriented Eutectic Growth
Authors: Wołczyński Waldemar
Published: January 2007

The concave‐convex interface shape formation of oriented eutectic has been analysed in microscopic scale. The proposed model has considered some physical phenomenona of eutectic growth, in particular preceding of the wetting phase by the leading one. The mechanism of curvature formation of the leading phase is different from that of the wetting one. The worked out model has been refered to the microscopic observations of the Pb–Cd eutectic interface shape. The sinusoidal approximation to the interface has been used to divide the lead distance into the leading phase protrusion and the wetting phase retraction. The behaviour of the contact angle of the wetting phase as a resultant of different physical factors' interaction during eutectic growth has been underlined.
A study of the Growth‐Temperature‐dependent Surface Morphology in InSb Liquid Phase Epitaxy
Authors: Chang L. B.
Published: January 2007

InSb LPE layers were grown on (111) InSb substrates, their phase diagram and growth rates studied. The InSb activity coefficient α(T), determined by fitting the experimental data, had a value of 2556–11.11 · T cal · mole−1. The terraces on the surface were reduced by increasing the temperature to 350 °C. Hall measurements of InSb/CdTe heterostructure failed due to the high Te segregation. The carrier concentration of these InSb epilayers, however, was determined by C‐V measurements with values between 7.5 · 1014 cm−3 and 5 · 1015 cm−3.
The Characteristics of EDTA's Transition Metal Complexes (III) The d‐d Transition Spectrum and Structure Characteristic of [Pb.Ni(HEDTA)H2O] Cl Crystal
Authors: Jianmin Li , Yugeng Zhang
Published: January 2007

The electronic absorption spectrum of crystals of the title compound [Pb.Ni(HEDTA) H2O] Cl was recorded and discussed quantitatively. Using ligand field theory and the radial wave function of bound Ni(II) ion, the d‐d transition energy levels of crystals of [Pb.Ni(HEDTA) H2O] Cl, Ca [Ni(EDTA)] · 4H2O, [Li.Ni(HEDTA) H2O], [NiH2EDTA)H2O] were calculated. The different structure characteristics of EDTA's metal complexes are evidently shown in their d‐d transition spectra.
Evaluation of Grain Surface Area in Heavily Arsenic‐doped Polysilicon
Authors: Kalainathan S. , Dhanasekaran R. , Ramasamy P.
Published: January 2007

A kinetic model based on thermodynamical concepts has been investigated to determine the grain size and its surface area in heavily arsenic‐doped polysilicon for various arsenic concentrations, annealing times and annealing temperatures. Computer simulation technique has been used to determine the grain boundary self‐diffusion of silicon atoms. The numerical analysis of our results shows that the grain surface area increases with annealing time and annealing temperature, but decreases with arsenic concentration. Our theoretical predictions have been compared with the available experimental results.
High Frequency Dielectric Relaxation of a Ferroelectric Liquid Crystal
Authors: Kresse H. , Tschierske C. , Joachimi D. , Kremer F. , Vallerien S.
Published: January 2007

Dielectric relaxation measurements on a optically active thiadiazole derivative in the frequency range from 1 MHz to 1 GHz gave relaxation frequencies between 100 MHz and 1 GHz in the smectic C* phase. This relaxation which is related to molecular reorientation processes around the long molecular axis is connected with a mean activation energy of 57 kJmol−1. A simple model of the energetic behaviour of this reorientation including the production of the spontaneous polarization is discussed.
Copper Incorporation in ZnO during LP‐MOCVD
Authors: Kaufmann Th. , Webert M. , Fuchs G. , Arnol H.
Published: January 2007

The MOCVD of ZnO layers, at a reduced reactor pressure and using DMZ.2THF and tertiary butanol as zinc and oxygen sources, resp., presents a number of advantages compared with the deposition at normal pressure. This also applies to the copper incorporation by means of cyclopentadienyl‐copper(I)‐triethyl phosphine. For the copper concentration in the ZnO layers, which linearly increases with the flow rate of the organocopper compound, values > 1020 cm−3 can be achieved. Even in case of high concentrations, the desired compensating effect of the copper is, for the time being, comparatively little, but increases considerably after a thermal retreatment of the layers. Some chemical‐defect aspects of ZnO will be discussed for the purpose of interpretation.
Characterization of the Microhardness of Ion‐implanted GaP
Authors: Ascheron C. , Neumann H. , Kühn G.
Published: January 2007

Implantation induced changes of the microhardness are studied in GaP single crystals which were bombarded with ions in the range of mass numbers M = 1–40. It is observed that point defects and incorporated hydrogen have a stronger hardening effect. The effect of defect complexes is lower, and amorphized layers are softer than crystalline layers.
The Growth of KDP Crystals and its Mechanism by Splicing Misoriented in Aqueous Solution
Authors: Feng Pan , Jinkui Liang , Genbo Su , Youping He , Rong Huang Bing , Yisen Huang , Qinglan Zhao
Published: January 2007

The growing characteristics of splicing misoriented KDP seeds of both bulk and thin pieces were investigated. The chemical etching method was used to determine the prismatic and Z‐plate surfaces of the crystals grown by splicing bulk KDP seeds. The X‐ray Lang topography method was employed to measure original thin platy crystals grown by splicing thin pieces of KDP seeds. From the results it can be concluded that when the misorientation of two seeds on the Z‐axis direction was about 1.5°, the crystal was grown successfully if the secondary capping was controlled properly. In comparison with the growth of splicing “parallel” seeds, the misorientation of both seeds increases such that the secondary capping becomes difficult, the sub‐grain boundary stretches longer, the stress field around the secondary cap enlarges and the crystals grown crack easily.
Preparation, Characterization and Sintering Behaviour of Complex Titanate Powders
Authors: Pfaff G.
Published: January 2007

Three methods were used for the preparation of complex barium titanate powders containing Sr, Ca, Mn and La or Pb, Ca and La, respectively: titanyl oxalate route, peroxide route, conventional solid state reaction. The powders are characterized with respect to their analytic and morphologic properties. The isothermal sintering behaviour is studied at 900, 1200, and 1320 °C. Powders prepared by the wet chemical synthesis show an excellent densification with final densities of about 97–98%. Possible sintering mechanisms are discussed.
Studies of Growth Mechanism and Sulfur Incorporation in VPE of GaAs under Nearly Equilibrium Conditions
Authors: Tempelhoff K. , Schmidt P. M.
Published: January 2007

Detailed investigations of growth rate of GaAs VPE‐layers and sulfur incorporation during crystal growth have been carried out under nearly equilibrium conditions at low temperatures (680 °C). The present investigation examines the dependence of growth rate and sulfur incorporation on the initial partial pressures (p°) of GaCl and HCl in the deposition zone. The observed deviation from the 1:1 proportion between GaCl before and HCl after the growth reaction will be discussed in a model of chlorine desorption by GaCl3. The sulfur concentration dependence in the grown layer indicates an identic growth mechanism and supports the idea of sulfur incorporation through an activated complex on the GaAs surface.
Growth of Lithium Niobate Single Crystal Fiber by an Edge–defined, Film‐fed Growth Method
Authors: Zhong H. , Hou Y. , Quan N. , Chen X. , Wang R.
Published: January 2007

Lithium Niobate (LiNbO3) single crystal fiber with 0.5 mm in diameter and 160–170mm long have been grown by an edge‐defined, film‐fed growth (EFG) technique. The morphology and microcracks of the fiber are studied. The mechanism of forming a single domain structure in the as‐grown LiNbO3 crystal fiber is discussed on the basis of the thermoelectric field model.
On the Influence of the Crystallization Conditions on the Microstructure of the Directionally Solidified Eutectic of the LiF – LiYF4 System
Authors: Barta Č. , Fendrych F. , Recker K. , Tříska A. , Wallrafen F.
Published: January 2007

This paper particularly deals with the transitions in degree and type of ordering of a given microstructure. As a model system the eutectic of the LiF – LiYF4 system was used for studies of transitions from ‘anomal’ microtextures with non‐cooperative production of seeds of both phases to the fibrous microtexture.

It was shown that even if the matrix phase LiYF4 contains a relative high volume ratio (36%) of LiF it is possible to create highly ordered fibrous microtextures with pronounced hexagonal ordering of particular LiF fibres. It was also shown that methods of image processing could be used for sensitive evaluation of small changes in degree of ordering of the microstructure.

These procedures make possible a deeper understanding of the influence of the solidification conditions on the microstructure of the directionally solidified eutectic and creates possibilities for optimalisation of the technological process.
Chemical Bond in AIIBV2 Systems from Magnetic Susceptibility Data
Authors: Vitkina Ts. Z. , Trukhan V. M.
Published: January 2007

Some peculiarites of chemical bond in AIIBV2 systems from the data on the magnetic susceptibility of the AIIBV2 compounds and their solid solutions are discussed. With this aim in view the magnetic susceptibility has been divided into the Langevin diamagnetic and van Vleck paramagnetic terms. The diamagnetic susceptibility of valence electrons, affecting the chemical bond in a crystal against the covalency parameter along the A – B, A – A, B –B bonds in AIIBV2 compounds, has been analysed. The covalency parameter of the AIIBV2 compounds has been evaluated.

Closeness of the covalency parameter values for monoclinic β‐ZnP2 and tetragonal CdP2, CdAs2, is evidently, one of the reasons for the solid solution formation between the above mentioned compounds.
Criteria for an Alternative Proposal for Crystal Growing by the Flux Method
Authors: Papadopoulos Ilias
Published: January 2007

Criteria are described for an alternative proposal for growing single crystals in the melt. Considering the solid state reactions between the components of the solved substances and the melting materials, a new heating process is discussed, taking into account the transformation temperatures of the intermediary products and also their reaction kinetics of formation and dissociation. As the most important parameter for the growth velocity is considered not the solubility of the initial components but the dissociation velocity of the by‐products.

At the start of crystallization an oscillating nucleation process is proposed with decreasing temperature amplitude. Hence, the number of critical nuclei in the neighbourhood of the supersaturated melt solution will be kept as small as possible. In this way, an optimal output and quality of a small number of single crystals was achieved.

These considerations were incorporated in a temperature program for the growth of single crystals by the flux method and they constitute an alternative to the usual application of this method.