bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface preparation of AB semiconductors (Cd3As2, Zn3As2, Cd3P2, Zn3P2) under ultra‐high vacuum conditions
Authors: Hupfer A. , Schulze S. , Hirsch D. , Żdanowicz L. 
Published: January 2007

AbstractThe UHV surface preparation of AB materials (crystals and thin films) has been monitored with XPS and AES. Clean and stoichiometric surfaces of AB crystals were prepared by means of low energy ion bombardment and subsequent low temperature annealing. Stoichiometric Cd3As2 and Zn3P2 thin films with very low amounts of C and O were deposited by the evaporation of bulk material in the UHV. The quality of prepared AB crystal and thin film surfaces was sufficient to carry out density of states investigations (UPS, RELS) with success.
Some aspects of the technology of lead salt diode lasers used in gas monitoring systems
Authors: Tomm J. W. , Sumpf B. , Herrmann Karin , Szczerbakow A. 
Published: January 2007

AbstractA rather simple method of lead salt diode laser fabrication is described. The optimization of the diffusion process forming the pn‐junction is especially discussed with regards to the various carrier concentrations of the as‐grown crystals. Liquid nitrogen cooled lead salt diode lasers of the described type meet all demands of a laser based air pollution monitoring device.
Point defects in GaP single crystals investigated by mechanical damping
Authors: Klimm D. , Paufler P. 
Published: January 2007

AbstractThe dependence of mechanical damping of LEC (liquid encapsulated Czochralski) crystals of GaP: S was measured in the temperature range 300… 600 K and at frequencies near 70 and 140 kHz, respectively. In samples of different stoichiometry two peaks could be observed: Peak A at 350 K and peak B at 450 K. Peak A is attributed to the relaxation of point defects near the surface, peak B is probably due to Ga vacancies.
Phase transition studies in the liquid crystal p‐cyanophenyl trans‐4‐pentylcyclohexane carboxylate
Authors: Gupta A. V. N. , Rao J. V. , Prasad N. V. L. N. , Venkatacharyulu P. 
Published: January 2007

AbstractInvestigations on specific volume and ultrasonic velocity measurements (at four different fixed frequencies) as a function of temperature are carried out in the liquid crystal p‐cyanophenyl trans‐4‐pentylcyclohexane carboxylate. From these studies various physical parameters like adiabatic compressibility, molar sound velocity, molar compressibility, van der Waals constant and intermolecular free lengths are evaluated. The variation of the order parameter with temperature at the four different fixed frequencies is also studied and the results are discussed.
Dielectric properties of ferroelectric lead hydrogen phosphate single crystals
Authors: Desai C. C. , Ramana M. S. V. 
Published: January 2007

AbstractThe ferroelectric lead hydrogen phosphate (LHP) single crystals have been grown by employing the gel technique. The controlled reaction between lead nitrate and orthophosphoric acid solutions by diffusion process in gel medium has been used. The dielectric constant (ϵ′) and the dielectric loss (ϵ″) have been measured for the first time as a function of frequency in the range 102 to 104 Hz. They have also been determined as a function of temperatures in the range 300 to 680 K. The polarisation effect contributing to the dielectric constant has been studied. It has been observed that the mechanism of the dielectric behaviour is different in the lower and higher temperatur and frequency ranges. The activation energy of the oscillators has been calculated and found to be 1.12 eV. Attempt has been made to draw some qualitative conclusions, taking in view, the existing theories of various kinds of polarization and implications have been discussed.
Microhardness investigations on gel‐grown barium cadmium oxalate mixed crystals
Authors: Prakash S. M. Dharma , Rao P. Mohan 
Published: January 2007

AbstractMicrohardness characteristics of barium‐cadmium oxalate crystals were undertaken using the indentation technique and the results there of are reported. The observed results were compared with the microhardness values of barium oxalate dihydrate and cadmium oxalate trihydrate crystals. The indentation induced cracks etched in 1N HCl reveal the surface of the dislocation pattern arround indentation mark. The mixed crystals show higher values of microhardness than the components barium oxalate dihydrate and cadmium oxalate trihydrate crystals.
Theoretical aspects of the crystal growth in gel
Authors: Desai C. C. 
Published: January 2007

AbstractCrystal growth by diffusion process in a gel medium has been utilized for a long time as method of simulation processes in the laboratory. The suitable theory of crystal growth in gels has been developed. Attention has been made mainly to the more general case in which the counter‐diffusion of two reacting substances occurs. The implications are discussed.
Diffusion of iodine in lead telluride
Authors: Assenov R. , Moshnikov V. A. , Yaskov D. A. , Andreev A. P. , Bestaev M. A. 
Published: January 2007

AbstractBy using the non‐stationary thermal‐probe method, investigations were carrieed out on the distribution of the coefficient of thermal electromotive force along the depth of monocrystals of lead telluride, subjected to isothermal saturating annealing in vapours of alloying compositions. The alloying composition consisted of powdered lead telluride, synthesized by the iodide method, and contained elevated concentration of the metallic component and iodine. The PbTe monocrystals were obtained from the vapour phase and had a natural cut. The results of the investigations testify to considerable changes in the concentration of the electrically active proper defects within the entire volume of the crystals, this being obviously connected with diffusion of vacancies from the crystal volume.
Model describing the resistance against structural changes and the hardness of crystalline solids
Authors: Heegn Hanspeter 
Published: January 2007

AbstractOn the basis of knowledge concerning the thermodynamic state and the structure of unelastically deformed solids the present paper derives a model for the description of the resistance of solids against mechanically induced structural changes. The concentration of dislocations, the external specific surface, the particle size of primary crystallites and the amorphization are important for characterizing the solids in the state of stress. The results of model calculations are compared with data available from literature on MOHS hardness and microhardness of crystalline solids. The results show a sufficient correlation independent of the nature of solids.
Microhardness studies of K1−xRbxCl crystals
Authors: Balaramaiah A. , Pratap K. J. , Babu V. Hari 
Published: January 2007

AbstractThe microhardness measurements have been made on pure crystals of KCl, RbCl and mixed crystals of K1−xRbxCl. Microhardness varies non‐linearly with composition being maximum near at the eqimolar composition. Microhardness values calculated from lattice parameter data are in good agreement with experimental data. The difference in the size of the ion constituting the mixed system is responsible for the internal strains giving rise to imperfections and inturn responsible for the non‐linear variation of microhardness with composition.
Phase transition studies in certain thermotropic liquid crystals thermal microscopy and DSC
Authors: Venkatacharyulu P. , Gupta A. V. N. , Rao V. Subba , Rao J. V. 
Published: January 2007

AbstractInvestigations on the phase transition studies in the thermotropic liquid crystals, (1) pcyanophenyl trans‐4‐propylcyclohexane carboxylate, (2) p‐cyanophenyl trans‐4‐pentyl‐cyclohexane carboxylate, (3) 4′‐n‐pentyloxy‐4‐cyanobiphenyl and (4) 4′‐n‐octyloxy‐4‐cyanobiphenyl are carried out by the thermal microscopy and the differential scanning calorimetric (DSC) studies. These studies reveal that the first three mesogens exhibit a single mesophase while the fourth one exhibits a smectic A phase in addition to the nematic phase. The textures exhibited by these mesogens in their mesophases and their transition temperatures, enthalpies and entropies are presented.
Evaporite minerals succession
Authors: Balarew Christo 
Published: January 2007

AbstractAn explanation is given for the crystallization succession during sea‐water evaporation, namely for the differences between the equilibrium solubility diagram of the marine‐type system and the “solar diagram”: The magnesium ions are known to exist in sea‐type solutions predominantly as hexaaqua complexes. Highest crystallization rates and lowest supersaturations required for nucleation should be exhibited by the magnesium salts, crystal structures of which incorporate unchanged hexaaqua magnesium complexes. For the salts with crystal structures in which the water molecules from the magnesium hexaaqua ions are partially or completely replaced by other ligands, the nucleations require high supersaturations and for this reason they do not appear in the “solar diagram”.This model is used to explain also some genetic pecularities of evaporite deposits: primary evaporite minerals are those which occur according to the “solar diagram” of crystallization. The evaporite minerals featuring in the equilibrium diagram and absent in the “solar diagram” occur in nature most frequently as secondary minerals.
Effect of structural transformations on the texture of NiFe base alloys
Authors: Betzl M. , Vlasova E. N. , Djakonova N. B. , Matorin V. I. 
Published: January 2007

Abstract1. Processes of texture formation were studied in three NiFe system alloys containing Mo and Ti (alloy No. 1), Cr, Ti and Al (alloy No. 2) and Co, Ti and Al (alloy No. 3). The deformation texture is identical in all alloys which agrees with the proximity of stacking fault energies as estimated from X‐ray data.2. Annealing leads to a pronounced diffusion and alteration of the texture in alloy No. 1, but does not alter the texture type and intensity in alloy No. 2, whereas in alloy No. 3 the typical strain texture components are intensified.3. Structure processes governing texture formation were identified as recrystallization in alloy No. 1, and oriented γ–γ′ transformation in alloys No. 2 and 3 where the intergranular boundaries were blocked by heterogenous precipitation of phases not possessing fcc structure.
Antistructure disorder and its relation to dislocations in III–V semiconductors
Authors: Figielski T. 
Published: January 2007

AbstractIntimate relationship between antistructure defects and dislocations occurs in GaAs which manifests itself as: (i) appearing of spatial correlation between grown‐in dislocations and the EL2 defects (component of the latter are AsGa antisites), (ii) similar suppression of the concentration of EL2 and dislocation density due to the doping with donor impurities, (iii) generation of AsGa antisites during the plastic deformation of a crystal. Al these effects can be understood in terms of the dislocation‐mediated generation of AsGa antisites via absorption of Asi interstitials at dislocation jogs. Large anion (cation) precipitates appearing at dislocations are pointed out to be important for both antisite and dislocation generation under certain conditions.
Electrical transport properties of CdTe:Sb films
Authors: Pratap K. J. , Nagabhushanam M. , Balaramaiah A. , Babu V. Hari 
Published: January 2007

AbstractHall coefficient and dc conductivity measurements are made on p‐type CdTe:Sb films grown by vacuum evaporation technique on glass substrate. The grain boundary potential barrier, which is found mainly to limit the mobility of carriers is calculated as a function of film thickness. The n‐type conduction is found to dominate over p‐type conduction above about 330 K. The ratio of electron to hole mobility is also calculated.
Thermal expansion in CuAlTe2 compound
Authors: Orlova N. S. , Bodnar I. V. 
Published: January 2007

AbstractThe lattice parameters a and c as well as the axial thermal expansion coefficients α ⟂ and α ∥ in the CuAlTe2 chalcopyrite‐type compound are determined as a function of temperature in the range from 80 to 650 K by a X‐ray diffractometry technique. The data obtained are used to evaluate the axial ratio c/a, the tetragonal distortion δ = 2 — c/a, the interatomic distances for CuTe and AlTe bonds and their temperature coefficients. It is found that the thermal expansion behaviour of CuAlTe2 is similar to that of other CuBIIICVI2 compounds in having a relatively small expansivity along the c‐axis and a large one in the perpendicular direction. When comparing the results for a series of the CuBIIICVI2 compounds (BAl, Ga, In; CS, Se, Te) it is shown that the correlations between the thermal expansion coefficients α ⟂, α ∥, αm, dδ/dT and the tetragonal distortion δ, as well as the molar mass of the compound take place.
High‐temperature heat capacity, thermodynamic properties and debye temperature of CuGe2P3
Authors: Neumann H. , Nowak E. , Omar M. S. 
Published: January 2007

AbstractThe heat capacity at constant pressure of CuGe2P3 is measured in the temperature range from 180 to 550 K. Standard enthalpies and entropies relative to 298.15 K are calculated from the heat capacity data. The Debye temperature in the high‐temperature limit is estimated to be about 710 K.
Annealing study of He‐irradiated Ni samples
Authors: Lemahieu I. , Segers D. , Deschepper L. , Dorikens‐Vanpraet L. , Dorikens M. , Stals L. , Mommaert C. , Severne G. 
Published: January 2007

AbstractPositron annihilation lifetime measurements were performed in helium‐irradiated Ni foils for annealing temperatures between 300 K and 1400 K. The samples were also examined by T.E.M. It is shown that immediately after the irradiations two kinds of vacancy clusters are present, some of them containing He‐ions and the others being empty. The empty vacancy clusters anneal out before 800 K, while the vacancy clusters containing He grow in size as a function of annealing temperature.
Influence of impurities on texture and structure formation through recrystallization of aluminium killed cold rolled steel
Authors: Iordanova I. , Bojinov V. , Iliev L. 
Published: January 2007

AbstractThe microhardness, electric resistance, volume of the unit cell, texture, form and size of ferrite grains and cementite particles depending upon recrystallization of cold rolled steel 08 killed with Al are investigated. Some conclusions about the morphology of solution of carbides and nitrides and about the influence of impurities on the recrystallization texture are drawn. Some recommendations about technology of annealing of preliminary aged cold rolled steel 08 killed with Al are given.
Positron lifetime studies in pure and chromium intercalated 2HNbSe2
Authors: Dhanalakshmi S. R. , Nagarajan T. , Ramasamy S. , Viswanath R. N. , Manivannan A. , Rao G. V. Subba 
Published: January 2007

AbstractThe layered 2 HNbSe2 belongs to a class of very interesting low dimensional conductors which exhibits CDW instability at 32 K. In our earlier paper we have established the two dimensionality of the Fermi surface, in these layered compounds by positron angular correlation technique. The reduction in Fermi level along the basal plane due to CDW transition has been already demonstrated by the Japanese group. But the sensitivity of positron lifetime and Doppler broadening techniques for CDW transition is controversial. The Japanese group report drastic changes in Doppler broadening parameters whereas the American group do not find such a change. Positron lifetime measurements have been performed on pure and Cr intercalated 2 HNbSe2 with Cr concentration 0.25, 0.33, and 0.5 with a view to assess the origin of the second lifetime component. The results show that there are two lifetime component τ1 ∼ 205 ps and τ2 ∼ 440 ps having intensity I2 ∼ 29%. On Chromium intercalation the intensity I2 decreases systematically. The trapping rate of positrons shows a systematic decrease with increase of Cr content indicating that the second lifetime arises due to positron annihilation in van der Waal's gap. The defect free annihilation rate λf was found to increase on intercalation indicating a charge transfer from the guest intercalates to the host MCh2 conduction bands.
OD approach to the polytypism in CdP2
Authors: Fichtner K. 
Published: January 2007

AbstractThe structures of CdP2 are described as stacking sequences of layers of CdP4 tetrahedra. On the basis of the OD theory of Dornberger‐Schiff, the stacking possibilities are derived and convenient stacking notations proposed. The idealized layer structure is given, the percentage of α‐CdP2 for any stacking sequence defined. The symbol of the OD groupoid family is P11(n)2m · (4) x, y with parameters x = y = 1/2 and (4+), (4−) as the two alternative transformations from layer to layer. The net constants are a = b ≈ 5.29 Å; the “thickness” of a layer is c0 ≈ 4.95 Å.
Microhardness scaling and bulk modulus‐microhardness relationship in AIIBIVC chalcopyrite compounds
Authors: Neumann H. 
Published: January 2007

AbstractAn analysis of experimental microhardness data shows that the microhardness of the AIIBIVCcompounds can be described by a simple scaling law which depends only on the unit cell volume and the melting temperature. On the basis of this result a simple bulk modulus — microhardness relationship is proposed and used to estimate the bulk moduli of the compounds. The results are compared with existing literature data.
Study of the growth mechanism in the ADP‐type anion‐doped crystals
Authors: Alemaykin F. M. , Kogan A. N. , Yudina T. B. 
Published: January 2007

AbstractA simultaneous simulation of the growth process in the A(K)DP‐type anion‐doped crystal and growing of this crystal from aqueous solution under controlled conditions has made it possible to analyse the mechanism of impurity influence on the growth rate of various crystal faces. The anisotropy of the face growth rate and the capture coefficient of various impurities by the faces have been determined by the difference in dissolution heats and in sizes of replacing ions. The increase in energy change, when the ion in a solution enters a crystal, causes an increase in the growth rate and the capture of impurities by the face with the largest change. Breaking of one of the joined faces and increased growth of another one resulted in forming of the new faces, i.e. in changing crystal morphology.
Physico‐chemical properties of pure and x‐ray irradiated single crystals of KAP
Authors: Varma K. B. R. , Raju A. R. , Rao K. J. 
Published: January 2007

AbstractSingle crystals of potassium hydrogen phthalate (KAP) have been grown by slow evaporation method from aqueous solutions. Thermal analyses indicate that KAP crystals decompose into phthalic anhydride and KOH around 520 K. Electrical properties of single crystals of KAP have been studied along with the effect of X‐ray irradiation of the crystals. The electrical transport appears to be associated with tunneling of protons. The irradiated crystal exhibits lower dielectric constant and higher ac conductivity.
Anisotropy effect of high‐momentum of ADAP in diamond‐like semiconductors
Authors: Arutyunov N. , Baltenkov A. , Segal I. 
Published: January 2007

AbstractA high‐momentum component of angular distributions of annihilation photons (HMC ADAP) has been studied experimentally and theoretically in single crystals of germanium, silicon and gallium arsenide and in a single crystal and polycrystal silicon. The model oe the process of positron annihilation with electrons of ion cores has been suggested and the calculations of HMC ADAP curves have been performed for crystallographic directions [111], [110] and [100] of a dimond‐like lattice. It has been established that ADAP anisotropy characteristics in a single crystal of germanium are slightly dependent on the temperature in the range of ΔT = 300÷930 K. It has been concluded that HMC ADAP anisotropy is caused by annihilation of thermalizod positrons with electrons of outer shells of ion cores in crystal lattices of dimond‐like semiconductors.
Annealing of electron irradiated GaP studied by positron lifetime technique
Authors: Sen Gupta A. , Moser P. , Corbel C. , Hautojärvi P. , Sen P. 
Published: January 2007

AbstractGaP single crystals were irradiated by 3 MeV electrons at 20 K to a dose of 4 × 1018 e/cm2. An isochronal annealing in temperature region 77 ÷ 650 K followed the irradiation. Positron lifetime measurement indicated the presence of irradiation‐induced vacancies in Ga sublattice. The vacancies disappeared at two stages observed at temperatures 200 ÷ 300 K and 450 ÷ 550 K.
The current understanding of epitaxial silicon doping in the light of modelling and theory development (VI) autodoping as a special mode of dopant incorporation
Authors: Kühne H. 
Published: January 2007

AbstractA consequent application of dopant incorporation theory to epitaxial silicon layer growth above buried layer regions explains the formation of an exponentially decaying dopant profile not only above that buried layer but also beyond of it. Taking into account desorption of dopants only and and neglecting readsorption of dopants on buried layer regions allows one to describe both vertical redistribution autodoping and lateral autodoping by the well known exponential expression that originally has been derived by Reif et al. in order to describe intended non‐steady state doping behaviour and later applied to lateral autodoping by Wong and Reif. Doping incorporation theory also explains the formation of a near‐equilibrium surface coverage with adsorbed dopants outside of buried layer during a preepitaxial baking process.Different dopant sources contributing to autodoping are characterized by different time constants. In this connection the adsorbed layer model derived by Tabe and Nakamura could be related to the action of two different dopant sources of autodoping where one of the two is characterized by a time constant being nearly infinite in number.
Interatomic interaction aspect of phase transition in AgInS2 crystals
Authors: Vaipolin A. A. , Rud Yu. V. , Rozhdestvenskaya I. V. 
Published: January 2007

AbstractThe structural parameters of two modifications of AgInS2 are determined. The geometrical model of phase transition is discussed. Crystallochemical comparison reveals the absence in the two modifications of significant differences in atomic interactions. The changes in atomic interaction with the temperature increase and the role of dynamical changes in phase transition are discussed.
Angular correlation studies of thin metal films
Authors: Aravin L. G. , Valiev K. A. , Goldanskii V. I. , Novikov Yu. A. , Rakov A. V. , Filimonov M. K. , Shantarovich V. P. 
Published: January 2007

AbstractAngular correlation of positron annihilation radiation is widely used in solid state physics studies (Goldanskii; Hautojärvi), in the defectoscopy of monocrystals in particular (Nielsen et al.). The interest to surface studies gave rise recently to very sophysticated and expensive method of positron beams (Goldanskii et al.). The recent study and recently published papers (Aravin et al.; Valiev et al.) demonstrate, however, that valuable information on surface properties can be obtained using the traditional angular correlation (AC) technique.
On segregation during crystal growth from a solution zone
Authors: Gille P. 
Published: January 2007

AbstractThe distribution in a mixed crystal A1−xBxC grown from an either (A, B)‐rich or C‐rich solution zone (e.g. travelling heater method or related techniques) is to be described by Pfann's zone melting function which depends on the segregation coefficient and a characteristic length. Using pseudobinary mole fractions x the characteristic length of the distribution function is not the actual length of the liquid solution zone but an effective zone length is to be regarded which may be considerably smaller or much bigger for C‐rich or (A, B)‐rich solutions zones, respectively.