bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThe 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

AbstractSingle 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

AbstractThe 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

AbstractA 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

AbstractLong‐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

AbstractMicroscopic 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.
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

AbstractThe 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

AbstractHydrolysis 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

AbstractMr = 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractA 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

AbstractInfrared 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

AbstractDielectric 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

AbstractSingle 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

AbstractThe 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

AbstractThis 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

AbstractIn 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

AbstractThe 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

AbstractTheoretical 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

AbstractAccording 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

AbstractThe 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

AbstractLPCVD 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

AbstractThe 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

AbstractThe 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

AbstractThe 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.