bluuebunny/crossref_metadata_2025 huggingface dataset:
The structure of rapidly solidified ribbons of Al‐12 at. % Zn alloy
Authors: Bartuška P. , Simerská M. , Syneček V. , Lašek J. , Heyroth W. , Löffler H.
Published: January 2007

The structure of melt spun rapidly solidified ribbons of the Al‐12 at.% Zn alloy has been investigated by scanning electron microscopy and by X‐ray diffraction. Four solidification processes differing in the extent of associated segregation of zinc have been found to be operative during the solidification of the ribbon. These successive processes beginning from above the sites of good contact of the melt with the rotating plane of the copper substrate are as follows: massive planar growth of grains, arrayed dendritic growth, unaligned growth of dendrites, and star‐like dendritic growth out from fragments of dendrites. Smaller grains resulting from the last two mentioned processes have been also found within the regions located above the sites of poor contact of the melt with the substrate (lift‐off regions). All indicated successive growth modes starting with the epitaxial regrowth of grains have been also found to proceed during the solidification of the melt flowed over the already solidified alloy ribbon.

Grain boundary precipitation of equilibrium β (≈︁ Zn) phase has been detected in all stages of solidification. High density of lattice defects built‐up during solidification is leading to the immediate intragranular heterogeneous precipitation of β phase at elevated temperatures within the two‐phase region without the formation of intermediate metastable precipitates.
Debye characteristic temperatures from X‐ray diffraction data and some thermal properties for AgGa1−xInxS2 solid solutions
Authors: Orlova N. S. , Bodnar I. V. , Kochkarik O. E. , Janovich V. D.
Published: January 2007

Investigations of the Debye characteristic temperature for the AgGa1−xInxSe2 solid solutions, calculation of some thermodynamic properties and analysis of its variation during substitution of Ga by In showed the increase of the molar volume, density, heat capacity, enthalpy, and decrease of the melting temperature, microhardness, thermal expansion coefficients, intrinsic energy with zero‐point energy, this giving evidence for a decrease of the forces of the interatomic interaction.
Crystal structure of 4‐(2‐hydroxyethyl)‐4‐aza‐5α‐androstan‐17β‐ol “HS‐478”
Authors: El‐shora A. I. , Gabala G. A. , Palmer R. A.
Published: January 2007

The crystal structure of HS‐478 (aqueous solvate) has been determined by direct method and refined by block diagonal least squares to R0 = 0.043. The intensity was measured in a four‐circle diffractometer in the ω/2θ scanning mode, CuKα radiation. The crystals are triclinic P1, a = 6.721(3), b = 66.532(3), c = 12.188(5) Å, α = 96.86(2)°, β = 82.82(2)°, and γ = 114.68(2)°. Rings A, B, C are chair whereas ring D is envelope. Rings A/B and B/C are trans fused, whereas rings C/D are quasi trans. The hydroxyethyl side chain connected to N(4) has conformation of (−t, t).
Crystal structure of n‐phenyl‐2,4,6‐triphenyl perchlorate, C29H22ClO4
Authors: Farag I. S. Ahmed , El‐Shora A. I. , Rybakov V. B.
Published: January 2007

The crystal structure of n‐phenyl‐2,4,6‐triphenyl perchlorate has been determined using the direct methods technique and refined to Ro = 0.055 and Rw = 0.056 for 1321 unique reflections measured on four‐circle diffractometer in the w scanning mode MoKα radiation. The crystals are orthorhombic, Pbca, a = 16.611(9), b = 16.625(6), c = 17.554(5) Å and Z = 8.

All rings are planar as expected within the experimental errors. Rings B, C, D, and E are twisted about the formal single bond by 72, 19, 95, and 78°, respectively, out of the plane of the central ring.
Structural characterization of alumina‐supported nickel molybdena catalysts
Authors: Sarbak Z.
Published: January 2007

The object of our studies was a NiMo/Al2O3 catalyst thermally activated in oxygen, hydrogen, and in a mixture of hydrogen and hydrogen sulfide. On the surface of the oxide form of the catalyst there are different species, among them dimeric and polymeric octahedrally coordinated Mo6+ ions containing oxygen bridges are found. The presence of structures resembling α‐ and β‐NiMoO4 and 6‐heteropolymolybdenates was determined. Reduction with hydrogen leads to formation of two nuclear structures with single and double bridges of [Mo25+ O3] and [Mo5+ O4] type, respectively, and partially reduced 6‐heteropolymolybdenates. On the other hand, when the reduction and sulfiding take place at the same time, then terminal oxide ions are partially replaced by sulfide ones. The presence of [MoO2S2]2− species has been observed, however, there is no evidence of the exchange —OH groups for —SH ones and exchange of oxygen bridged ions for sulfur ions. It has been also noted that the subsurface structures remained intact after reduction and sulfiding.
Thermochemical analysis of native point defects and substitutional carbon and boron in GaAs crystal growth
Authors: Wenzl H. , Mika K. , Henkel D.
Published: January 2007

The phase extent of GaAs has been analyzed and compared with published phase diagrams as related to total and partial point defect equilibria including charged and uncharged Frenkel, Schottky, antisite defects and substitutional carbon and boron on both sublattices.

The well‐known transition between semiconducting and semi‐insulating behaviour at 300 K as a function of melt stoichiometry in LEC crystals can be reproduced in our model in which complete equilibrium exists above, only electronic equilibrium below a freeze‐in temperature of 1100 K.

The corresponding model standard enthalpy of formation of neutral Schottky defects is 4.0 eV, of a pair of neutral uncorrelated antisite defects 3.8 eV, of neutral Ga Frenkel defects 4.1 eV and of neutral As Frenkel defects 3.6 eV.

Defect reactions in cooling processes after crystal growth are discussed and shown to be quite different for crystals with high or low dislocation density. Semi‐insulating behaviour requires the existence of carbon acceptors if dislocations provide internal sources and sinks for point defects. For ideal crystals carbon would not be necessary.

The possible site distribution of C and B is analyzed in its dependence on temperature and chemical potential of As.

Constitutional supercooling is negligible in LEC growth. Macrosegregation is severe if the As fraction in the melt deviates more than ±0.02 from the stoichiometric value 0.5.
X‐ray investigation on GaAlAs/GaAs epilayers bending at temperatures 77–750 K
Authors: Leszczynski M.
Published: January 2007

The Bond method of precise lattice constants measurements and double crystal (+, −) (004) reflections were applied to measure lattice constants, lattice mismatch, thickness of the layers and samples bending in temperature 77–750 K. The results enabled to calculate the ratio of GaAs and Ga1−xAlxAs elastic constants as well as thermal expansion coefficients.
Crystal and molecular structures of N‐alkyl‐N, N‐dimethyl‐3‐(heptamethyltrisiloxan‐3‐yl) propylammonium bromides
Authors: Ramm M. , Schulz B. , Sonnek G. , Schmaucks G.
Published: January 2007

C16H42NO2Si3Br: Mr = 444.76, monoclinic space group P 21/c, a = 23.300(8), b = 8.918(4), c = 13.403(2) Å, β = 101.69(4)°, V = 2727(1) Å3, Dx = 1.08 Mgm−3, Dexp = 1.06 Mgm−3, Z = 4, F(000) = 932, λ(MoKα) = 0.71069 Å, μ = 16.3 cm−1. The crystal structure was determined by direct methods and refined by least‐squares procedure to the discrepancy factor R = 0.117.

C15H40NO2 Si3Br: Mr = 430.34, monoclinic space group P21/c, a = 23.460(4), b = 8.518(2), c = 13.403(2) Å, β = 102.03(2)°, V = 2619(1) Å3, Dx = 1.09 Mgm−3, Dexp = 1.07 Mg−3, Z = 4, F (000) = 920, λ(MoKα) = 0.71069 Å, μ = 33.9 cm−1. The crystal structure was determined by least‐squares refinement of the structure model derived from structure determination of C16H42NO2·Si3Br to the discrepancy factor R = 0.099.

C16H42NO2Si3Br: Daten siehe oben.

C15H40NO2Si3Br: Daten siehe oben.
Chemistry of organic eutectics: Phenanthrene — benzoic acid and phenanthrene — cinnamic acid systems
Authors: Rai U. S. , Shekhar H.
Published: January 2007

Solid‐liquid equilibrium data for binary systems of phenanthrene with benzoic acid and cinnamic acid, expressed in the form of temperature‐composition curves, show the formation of a simple eutectic in each case. Linear velocity of crystallisation (v), studied by capillary method at different undercoolings (ΔT), suggests the applicability of Hillig‐Turnbull equation, v = u(ΔT) n, where u and n are constants depending on the nature of solidification. Data on heats of fusion of pure components and eutectics, determined by the DTA method, infer appreciable interaction among the components in the eutectic melts. To highlight the nature of interactions among the components forming the eutectic melt, the excess thermodynamic functions such as hE, sE, and gE were computed. Microscopic studies reveal that the structure of eutectic is different from those of the parent components. Infrared spectra, recorded in the region, 4000 —625 cm−1, indicate weak interactions among the components in the eutectic.
Study of sintering processes in copper and nickel by positron annihilation
Authors: Krause R. , Schatt W. , Vetter B. , Polity A.
Published: January 2007

In the advanced stage of non‐isothermal sintering, vacancy clusters are present as prevailing type of defects. Their concentration considerably decreases at further temperature increase, and it can be concluded that thermally activated conversion of multiple vacancies into climbable dislocations takes place. Hence, in conformity with recent experiments, coincidence of intensive material transport (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document} e‐maximum) and decrease of defect concentration (recovery) can be understood.
Infrared reflectivity of ZnIn2Te4
Authors: Neumann H. , Kissinger W. , Lévy F. , Sobotta H. , Riede V.
Published: January 2007

Infrared reflectivity spectra of ZnIn2Te4 single crystals are measured at room temperature in the wavenumber range from 170 to 4000 cm−1. The spectra reveal a single vibrational mode the frequency of which compares well with the frequencies of the high‐energy infrared active modes in HgIn2Te4, CuInTe2 and AgInTe2. It is concluded that these modes are sphalerite‐like in nature and that they are essentially determined by the properties of the In—Te bond.
Mechanical characteristics of the NaCl: Eu2+ crystal system
Authors: Suszyńska M. , Nowak‐Woźny D.
Published: January 2007

Yield strength of NaCl: Eu2+ monocrystals was studied as function of both the dopant concentration and the annealing parameters. Main attention was paid to the strengthening mechanisms induced by the presence of europium related second phases the structure of which was controlled by means of optical methods.

Depending on the nature of the second phases and their crystallographic relations with the matrix, two strengthening phenomena have been evidenced: this related with the presence of penetrable and that related with inprenetrable second phase particles. As far as the former ones can be sheared along with the matrix, the later — are overcomed due to a looping mechanism resembling the behaviour of metal alloys with the fcc — type of structure.
Phase formation at constantly increasing supersaturation: Electrolytic nucleation at galvanostatic conditions
Authors: Dobreva A. , Gutzow I.
Published: January 2007

A simple theoretical approach treating the kinetics of phase formation at constantly increasing supersaturation is developed. The process of electrolytic nucleation in galvanostatic regime i.e. at time changing cathodic overpotential is analyzed in terms of this formalism.

It is found that the atomistic model of nucleation has to be applied in order to describe quantitatively the process of electrolytic phase formation.
Electrical conductivity and thermoelectric power of lithium‐cadmium ferrites
Authors: Ravinder D. , Rao T. Seshagiri
Published: January 2007

The electrical conductivity (σ) and thermoelectric power (Q) of polycrystalline lithiumcadmium ferrites having the chemical formula Li0.5–x/2CdxFe2.5–x/2O4 where (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) have been investigated as a function of temperature. Lithium‐cadmium ferrite with x = 0.4 is found to possess minimum electrical conductivity and lowest Seebeck coefficient. Plots of log (σT) versus 103T are almost linear and have shown a transition near the Curie temperature except in the case of cadmium ferrite. The Seebeck coefficient is negative for all the compositions showing that these ferrites behave as n‐type semiconductors. The values of charge carrier concentration and mobility have also been computed. The properties of cadmium‐substituted lithium ferrites have been correlated with those of zinc‐substituted lithium ferrites, cadmium and zinc being two non‐magnetic divalent ions occupying essentially tetrahedral A sites when substituted in ferrites.
Equilibrium vapour pressures over NaCl‐AgCl melts
Authors: Lenchev A. , Trifonova E. P.
Published: January 2007

The variation of vapour pressures over NaClAgCl melts with increasing of AgCl mole fractions in the interval (0.00–0.33) has been studied at 1073 K by gas transport experiments. The vapour pressures of the individual species of silver chloride [(AgCl), (Ag3Cl3)] and of sodium chloride [(NaCl), (Na2Cl2)] have been calculated using thermodynamic data. The experimental and calculated results have been used for evaluation of the vapour pressures of the complex species Ag2NaCl3 and AgNa2Cl3 at the upper experimental conditions. The equilibrium constants of the following gas‐phase reactions have been computed: 2 AgCl + NaCl ⇌ Ag2NaCl3, Kp1073K = 2.57 · 106, AgCl + 2 NaCl ⇌ AgNa2Cl3, Kp1073K = 1.19 · 107.
Dislocation studies by chemical etching on solution‐grown NaSbF4 and Na3Sb4F15 single crystals
Authors: Benet Charles J. , Gnanam F. D.
Published: January 2007

An attempt has been made to study the etch pit dislocations of isolated as well as matched pairs of cleavage planes of solution grown NaSbF4 and Na3Sb4F15 single crystals when etched with analar grade methyl alcohol and ethyl alcohol. On etching of cleavage faces the pits nucleate at the intersection sites of dislocations with the cleavage face. On successive etching of a cleavage face, arrays of triangular shape etch pits are observed. After prolonged etching some of the etch pits disappear. These pits are curved and terminated indicating that they are crystallographically non‐oriented. One‐to‐one correspondence with respect to number, shape, position and structure of the pits has been established by etching of a matched cleavage face. The etch pit densities of both NaSbF4 and Na3Sb4F15 crystals are found to be 103 per cm2.
Electrical Conductivity and Thermoelectric Power of LithiumZinc Ferrites
Authors: Ravinder D. , Seshagiri Rao T.
Published: January 2007

Electrical conductivity (σ) and thermoelectric (Q) of polycrystalline lithium‐zinc ferrites of different compositions was investigated as a function of composition and temperature. Plots of log (σT) versus 103/T are almost linear and show a transition near the Curie temperature. The activation energy. in the ferrimagnetic region is in general less than that in the paramagnetic region. The carrier concentration and mobility of charge carriers has been discussed as a function of composition and temperature.
The thermodynamic equilibrium of the formation process of High‐Tc superconducting phase YBa2Cu3O7−x
Authors: Huan Le Van , Tuong Le Thi Cat
Published: January 2007

Analysing the equilibrium state of the formation reaction of the high‐Tc superconducting phase 1:2:3 (YBa2Cu3O7−x) on the base of the pressure‐temperature‐oxygen content (P‐T−x) correlation research and using the Van't‐Hoff equation, the Gibbs free energy (ΔGm) of the reaction has been calculated for the first time. It is seen that the absolute value of ΔGm is not large and of the order of 2.5 kcal · mole−1. This leads to an instability of the 1:2:3 phase. Also, from the calculated values of ΔGm relative stability regions of the 1:2:3 phase are determined for different values of x. Combinatively analysing the relation lg P = A−B/T (where A – the x‐dependent constant, and value of B was determined to be equal to 10518 atm. K) and the value of ΔGm, we come to the conclusion that the synthesis of YBa2Cu3O7 − x when x → 0 must be carried out under high oxygen pressure and low temperature for a lasting time, because the reaction rate is limited by slow diffusion in the solid phase.
Growth, structure and properties of thin monocrystalline InSb films grown by recrystallization in a narrow gap
Authors: Sheftal R. N. , Zybtsev S. G.
Published: January 2007

The results of investigation of recrystallization kinetics of (≦ 500 Å) InSb films are described with the aid of a laser refractometer. The thermodynamic process characteristic considered to the gap thickness and substrate material are investigated. It was revealed that the method of producing a protective SiOx coating greatly affects the electric properties of InSb films.
Improving the batch crystallizers operation
Authors: Belcu M. , Pincovschi E.
Published: January 2007

Using a mathematical model, from the literature, for the potassium sulphate crystallization, a computer programme was elaborated, aiming to optimize the operation of batch crystallizers through the minimization of the formed crystals number. Owing to the simplifications imposed by the numerical calculation a semnificative reduction of the crystals number was not obtained, comparatively with the constant supersaturation crystallization process, considered as a standard mode of operation. However, the model pointed out the direction for further process improving. Through systematical search, by generating different continuously diminishing functions for the supersaturation value, operating policies were founded, conducting to the reduction of the number of crystals formed in the process.
Some correlations in liquid phase growth (II)
Authors: Peev N. S.
Published: January 2007

In the present work some general relationships are given for the process of liquid phase epitaxy, and here are considered the most widely used methods: 1) Equilibrium cooling technique; 2) Step cooling technique; 3) Supercooling technique.
Crystal structure of a new chalcone compound prepared from khellinone
Authors: Ahmed Farag I. S. , Abd el‐hafez O. M. , Rybakov V. B.
Published: January 2007

Claisen‐Schmidt condensation of Khellinone (4,7‐dimethoxy‐5‐acetyl‐6‐hydroxy)benzofuran with 2 thiophenalyde led to synthesis of the new biologically active 4,7‐dimethoxy‐5[γ(2‐thiophene)‐ß‐propene‐α‐one]‐6‐hydroxy‐benzofuran. The crystal structure of this new chalcone was confirmed using X‐ray structure analysis.

The structure data obtained for a single crystal of the new chalcone are: Monoclinic, a = 8.845(3), b = 7.813(3), c = 22.146(8) Å; β = 96.51(2)°, V = 1520.6 Å3, Z = 4; Dx = 1.44 g · cm−3, space group P21/c, R = 0.067, Rw = 0.069.

The intensity data were collected on an Enraf Nonius CAD‐4 computer controlled diffractometer using MoKα radiation. The structure was solved by the direct method and refined by full matrix least squares using anisotropic temperature factors of all atoms, except for hydrogen atoms, which were treated isotropically.
Low‐temperature LPE technique for the performance of visible AlGaAs (SC) lasers
Authors: Díaz P. , Prutskij T. A. , López F.
Published: January 2007

The possibilities of the low‐temperature (LT)‐LPE technique in the performance of visible AlGaAs laser diodes are studied. Low current density visible lasers λ ˜ 746 nm has been fabricated and characterized. The laser diode structures are of the separate confinement type (SC) to obtain low threshold current (Jth = 190 A/cm2 at λ = 848 nm for a cavity length L = 1.15 mm). The threshold current density Jth versus lasing wavelength λ characteristic, as well as the dependences of the threshold current density Jth and the reciprocal of differential quantum efficiency 1/ηd with the cavity length L are reported. The expected linear behaviour of the Jth and 1/ηd with the cavity length characteristics appears to break down for the shortest cavity length which is larger for shorter lasing wavelengths.
Crystal‐chemical properties of compounds with a pyrochlore structure in the Ln2O3TiO2 (Ln = Pr, Nd, Sm, Eu, Gd, Tb) systems
Authors: Sidorova N. M. , Kartenko N. F. , Degen M. G. , Glushkova V. B.
Published: January 2007

Compounds of the pyrochlore structure in the Ln2O3TiO2 (Ln = Pr  Tb, without Pm) systems were synthesized. Their crystal‐chemical properties were determined (crystallization temperature, unit cell parameters and their temperature dependences, refractive indexes and densities). Models of defect pyrochlore structure of Pr2O3 · 3.75 TiO2, Nd2O3 · 3.5 TiO2, Sm2O3 · 3 TiO2 compositions were suggested.
Infrared lattice vibrations of CdIn2Se4
Authors: Neumann H. , Kissinger W. , Lévy F. , Sobotta H. , Riede V.
Published: January 2007

Infrared reflectivity spectra of CdIn2Se4 single crystals are measured at room temperature in the wavenumber range from 180 to 4000 cm−1 for the polarization directions E ⟂ c and E ‖[112]. The spectra reveal two vibrational modes with nearly the same frequencies for both polarization directions. The frequencies of the modes with highest energy compare well with the corresponding mode frequencies in ZnIn2Se4, CuInSe2 and AgInSe2. It is concluded that these modes are sphalerite‐like in nature and that their frequencies are essentially determined by the properties of the InSe bond.
Characterization of interface states at Ni/n‐Si Schottky barriers from I – V characteristics
Authors: Sahay P. P. , Srivastava R. S.
Published: January 2007

Experiments were performed on Ni/n‐Si(111) Schottky diodes fabricated by the thermal vacuum deposition of nickel on n/n+ Si epitaxial wafer at ˜ 10−5 torr pressure. The non‐equilibrium occupation functions of the interface states were studied using the Shockley‐Read‐Hall (SRH) theory and considering the charge exchange between metal and interface states. Interface states density was determined from (I ‐ V) characteristics using metal‐interfacial layer‐semiconductor (MIS) structure. The density was found to be in the range of 1012 eV−1 cm−2 with a broad peak in the band gap of Si at about 0.554 eV below the conduction band edge.
The significance of X‐ray investigations for the classification of multicomponent systems with mixed crystals in a solid phase
Authors: Dejewska B.
Published: January 2007

The X‐ray investigations of solid phases in the multicomponent systems KClKBrH2O, K2SO4(NH4)2SO4H2O and KNO3NH4NO3H2O were conducted and the crystal lattice parameters of mixed crystals forming in these systems were determined. It was confirmed that in the KClKBrH2O system the continuous solid solutions were formed and in the K2SO4(NH4)2SO4H2O system the solid solutions with a miscibility gap were formed. In the KNO3NH4NO3H2O system the presence of two series of mixed crystals, namely the mixed crystals between ammonium nitrate and the double salt KNO3 · 2 NH4NO3 and between potassium nitrate and the same double salt was confirmed. In this system a wide region of discontinuity (for xNH4NO3 = 0.083 – 0.67) also occurred.

According to Roozeboom's classification, the KClKBrH2O system belongs to the 3rd type, the K2SO4(NH4)2SO4H2O to the 5th type (the discontinuous mixed crystals, the systems of peritonic type) and the KNO3NH4NO3H2O system is not comprised in this classification.
Influence of the Form Factor on Homogeneous Nucleation Kinetics
Authors: Kožíšek Z.
Published: January 2007

Influence of the cluster form on the nucleation rate and the transient time is studied. Relatively small increase of a geometric form factor γ (γ ∼ An/V2/3n, where An denotes the surface area and Vn the volume of the nucleus of n molecules) provokes the massive decrease of the nucleation rate and small increase of the transient time.
TEM Studies of Er+ – implanted CdTe
Authors: Morawiec J. , Gołacki Z.
Published: January 2007

The structure and the depth distribution of radiation damage caused by erbium implantation (Ei = 100 keV, D = 5 × 1015 cm−2, Ti = LNT) in 〈111〉 cadmium telluride have been investigated by means of planar‐view and cross‐sectional TEM techniques. It is found that the implantation disturbes the CdTe target up to the depth well‐beyond the calculated projected range (that is ≳ × 5Rp). The resulting damage structure consists of well‐defined defects: precipitates, stacking faults, dislocation loops, and dislocation networks, which appear to be segregated with depth forming a sequence of homogeneously faulted zones. This characteristical and deep damage is suggested to be formed on dynamic annealing in response to internal stresses (caused by lattice parameter mismatch) which are high enough to produce plastic relaxation with dislocation generation and slip.

This study is aimed at describing the ion‐implantation‐induced damage in single crystal cadmium telluride caused by Er+ ions by means of transmission electron microscopy.
Photoconductivity Spectra of n‐type CuInSe2 Single Crystals
Authors: Slifkin M. A. , Al‐Rahmani A. , Imanieh M. , Tomlinson R. D. , Neumann H.
Published: January 2007

Photoconductivity spectra of n‐type CuInSe2 single crystals are measured in the photon energy range hv = 0.75 – 3.1 eV and as a function of temperature in the range T = 80 – 320 K. It is found that the photoconductivity of as‐grown crystals is a nearly pure surface effect, while sensitization of the crystal volume is observed only after sufficiently long annealing in the presence of powdered material. To explain the temperature dependence of the photoconductivity carrier trapping processes must be taken into account.
X‐Ray Diffraction Studies on Molecular Semiconductors Based on Charge‐Transfer Complexes of Substituted Phenothiazines with 2,3‐Dichloro‐5,6‐dicyano‐p‐benzoquinone
Authors: Singh Ram Adhar , Singh Ranjana , Verma S. M.
Published: January 2007

X‐ray powder diffraction data on the molecular semiconductors based on the 1:1 charge‐transfer complexes of the electron donors, viz. phenothiazine (PTZ), 2‐chlorophenothiazine (CPZ), 2‐acetyl phenothiazine (APZ) and 2‐(trifluoromethyl)‐phenothiazine (TPZ) with 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ) have been reported in this paper. The indexing has been done by Ito's method. All the complexes have been found to have orthorhombic crystal structures. The lattice parameters for the individual complexes are as follows: (i) PTZ‐DDQ: a = 6.020 Å, b = 9.775 Å, c = 24.280 Å; (ii) CPZ‐DDQ: a = 5.830 Å, b = 8.070 Å, c = 20.280 Å; (iii) APZ‐DDQ: a = 5.055 Å, b = 7.955 Å, c = 19.520 Å; (iv) TPZ‐DDQ: a = 5.130 Å, b = 8.195 Å, c = 19.850 Å.
RHEED Studies of MBE‐grown Aluminium Layers on {111}‐Oriented Silicon Substrates
Authors: Büschel M. , Tempel A. , Zehe A.
Published: January 2007

Thin Al‐layers were prepared by Knudsen‐type evaporation of Al onto {111} Si in a custom built UHV‐reactor. Epitaxial growth was found on clean substrate surfaces with (7 × 7) reconstruction. In situ RHEED provides the epitaxial relationship
equation image

The epitaxial films show a twelve‐fold symmetry axis according to the combination of the 4‐fold and 3‐fold symmetry of the {001} deposit plane and of the substrate surface, respectively.
Influence of Profile Parameters on the IR Thickness Measurement of Thin Silicon Epitaxial Layers
Authors: Quick Ch. , Hild E. , Schley P. , Quick J.
Published: January 2007

For IR thickness measurements of very thin silicon epitaxial layers (depi < 3 μm) on silicon substrate the influence of the concentration profile of free carriers in the whole system is not negligible. The effects of most important profile parameters on the IR reflectance spectrum of silicon epitaxial layer systems are analysed by mathematical simulations. The theoretical results are confirmed by experimental ones.
Structural and Density Changes of Rhenium Single Crystals Upon Rolling and Annealing
Authors: Larikov L. , Belyakova M. , Rafalovski V.
Published: January 2007

The rhenium crystals were rolled in the {1000} 〈1120〉 orientation. Rolling produces cracks in crystals at low deformation (ϵ = 30%). It has been shown that microcracks in the volume of the crystal arise at a more earlier deformation stage than visible surface cracks.

Recrystallization during subsequent annealing is strongly intensified with the start of crack formation. Stepwise facets of recrystallizated grains are often observed, this fact being connected with twinning lamellae recrystallization. Microcracks in the crystal body are completely eliminated during high temperature annealing. This process caused by diffusion over microcracks surfaces.
MOVPE of InP Using Trimethylindium – Trimethylamine Adduct
Authors: Keller B. P. , Oelgart G. , Pickenhain R. , Grummt G. , Seifert W.
Published: January 2007

Growth of InP layers by MOVPE using trimethylindium‐trimethylamine (TMIn–TMN) is described. Low temperature photoluminescence results reveal the high crystal quality indicated by the well resolved excitonic spectra and high internal quantum efficiency. A strong near‐gap luminescence degradation with decreasing substrate temperature during the growth corresponds with the increasing deep level concentration estimated by the DLTS‐investigations. In the specimens prepared at higher temperatures carbon and zinc are believed to be the main residual acceptors. From C–V data free carrier concentrations of 1015 cm−3 were obtained.
The Influence of Surface Modification upon the Angular Distribution of Slip Traces on the Surface of Polycrystalline F.C.C. Metals
Authors: Preuss E. , Preuss H. H. W.
Published: January 2007

Surface modification by ion implantation leads to a smaller portion of grains of a polycrystalline metal showing slip traces as a result of cyclical deformation. The analysis of the azimuthal distribution of the slip traces gives an approach to explain this experience in more detail. Analytical and numerical calculation of the azimuthal distribution of slip traces under consideration of the slip geometry relative to the free surface leads to azimuthal distributions as experimentally determined for polycrystalline nickel after implantation with N+‐ions and following cyclic fatigue with constant amplitude of plastic strain ϵpa = 10−4.
The d‐d Transition Spectra of Copper (II) Complexes in Different Coordination Environment. Study on Cu(TTA)2 and Cu2(sacch)4(Im)4
Authors: Jianmin Li , Yugeng Zhang
Published: January 2007

The d‐d transition spectra of Cu(TTA)2 and Cu2(sacch)4(Im)4 complexes crystals have been determined. Using the crystal structure data, their d‐d transition energy levels are calculated by the program which we used for the calculation of field theory. The calculated values are in good accordance with the experimental results. Compared to the copper(II) complexes in various coordination environments, their d‐d transition spectra have an evident difference.
X‐ray Diffraction Studies on the Molecular Semiconductors Based on the Charge‐Transfer Complexes of Some Substituted Phenothiazines with Iodine
Authors: Singh Ram Adhar , Singh Ranjana , Verma S. M.
Published: January 2007

The powder X‐ray diffraction data on some molecular semiconductors based on the charge transfer complexes of three substituted phenothiazines viz., phenothiazine (PTZ), 2‐chlorophenothiazine (CPZ), and 2‐(trifluoromethyl)phenothiazine (TPZ) with molecular iodine have been reported in this paper. The indexing of the data has been done by Ito's method. All the complexes have been found to have orthorhombic crystal structures. The lattice parameters for the individual complexes are as follows:

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These results indicate that the segregated stacking of mixed valence with neutral and cationic donor moieties and polymeric iodide species, two pentaiodides linked with one trüodide forming a staircase delocalized structure, are present in these complexes. This may be possibly the reason for high electrical conductivity of these complexes. However, the charge transfer complexes of iodine with 2‐acetylphenothiazine (APZ), N‐acetylphenothiazine (NAPZ) and N‐benzoylphenothiazine (NBPZ) give no diffraction patterns indicating that the molecular semiconductors based on these complexes exist in amorphous form. This is further supported by very low electrical conductivities of these complexes. This structural information is quite useful in discussing the electronic properties of this class of molecular semiconductors.
Investigations Concerning the Quasi‐binary System V2O5 – Nb2O5
Authors: Schadow H. , Oppermann H. , Grossmann O. , Krzewska K. , Wehner B.
Published: January 2007

In examining the pseudobinary system V2O5 – Nb2O5 it was possible to isolate, by systematic transport reactions, just one stable compound of the mean composition V1.057Nb8.943O25 in addition to the boundary phases, which is in contrast to the data given in the literature. The phase width of this compound is very small and within the confidence limits of the analytical method of determination of 0.2 p.c. A maximum of 50 ppm Nb2O5 only dissolve in V2O5. Determining the solubility of V2O5 in Nb2O5 failed, because the two‐phase products resulting during the chemical transport of the respective samples could not be separated exactly.
RHEED Investigations on Low‐temperature Thermal SiO2 Films
Authors: Popova L. I. , Peneva S. K. , Tcukeva E. A. , Atanassova E. D.
Published: January 2007

The structural changes in thermal SiO2 films grown at 1123–1173 K in a double walled furnace tube with chlorine between the inner and the outer tube are studied. The layers have a higher degree of crystallinity in comparison with the layers grown by standard high temperature dry oxidation (1273 K). A difference between the crystalline type structures of SiO2 films on p‐ and n‐Si is observed. The increase of the growth temperature from 1123 to 1273 K increases the variety of crystalline structures in the layers but decreases strongly their quantity and makes the films predominantly amorphous.
Thermoluminescence of Sr1–xEuxF2 + x Solid Electrolytes
Authors: Somaiah K. , Sharma T. A. V. , Nambi K. S. V. , Hartog H. W. Den
Published: January 2007

Thermoluminescence (TL) studies have been carried out in different compositions of Sr1–xEuxF2 + x mixed crystals as a function of X‐irradiation time. Three groups of TL glow peaks in the temperature ranges (340, 360 ∼ 370 K), (460 ∼ 475, 540 ∼ 575 K) and (615 ∼ 635, 680 ∼ 720 K) are identified. The growth rates of different glow peaks have been compared with each other to estimate the growth kinetics. The three groups of TL glow peaks are attributed to thermal ionization of radiative impurity centers, different stages of F‐centers and other kinds of defect centers such as F‐interstitials. The shift in the glow peak maxima is perhaps due to unassociated impurities surrounding F‐centers causing a change in configuration. The concentration quenching of TL output due to increased europium is pertinent in Sr1–xEuxF2 + x mixed system.
Some Physicochemical Studies on Binary Organic Eutectics and 1:2 Molecular Complexes
Authors: Rai U. S. , George Santhi
Published: January 2007

Benzidine‐m. aminophenol system gives a double simple eutectic type phase‐diagram showing the formation of a 1:2 addition compound with congruent melting point surrounded by two eutectics on either side. The linear velocity of crystallization data on pure components, eutectics, and addition compound suggest square relationship between growth velocity and undercooling. From the X‐ray diffraction studies it can be inferred that the eutectics are not a simple mechanical mixtures of two components. Whereas microstructural investigations suggest faceted growth of the addition compound and a typical characteristic growth of the eutectics, spectral studies indicate the formation of intermolecular hydrogen bonding between two components forming the molecular complex.
High‐Pressure X‐ray Diffraction Studies on Organic Crystals
Authors: Katrusiak Andrzej
Published: January 2007

The high‐pressure X‐ray diffraction technique, commonly applied for inorganic crystals, is discussed in a view of its application for laboratory studies on molecular crystals of organic compounds – particularly when the weak X‐ray scattering of such specimens causes experimental difficulties. To minimize the background‐to‐signal ratio, relatively big crystal samples (ca. 0.005 A3) were used and the mechanical properties of the gasket material were applied to obtain the optimum experimental conditions for pressure generation and lowering the background of reflections. The mechanical properties of tungsten, Inconel, and hardened steel gaskets are different and these properties can be helpful in planning high‐pressure measurements with large high‐pressure chamber to contain a big crystal sample. Several characteristic features of organic crystals – like their strong compressibility (depending on the nature of intermolecular interactions) and pressure‐dependence of thermal vibrations of atoms – can have a direct impact on the conditions of high‐pressure experiments. The properties of molecular crystals of organic compounds have been discussed on the basis of several high‐pressure structural studies, mainly on simple cyclic β‐diketoalkanes (enol forms). It has been attempted to assess the feasibility of investigating the details of molecular structure at high pressures by X‐ray laboratory studies. A systematic pressure‐induced change in the length of double C  O bonds is observed in this group of compounds, which can be correlated with the compression of the H‐bonds involving the carbonyl groups.
Velocities of Disappearance and Lifetime of Faces of Growing Crystals
Authors: Szurgot M.
Published: January 2007

The formulae for absolute Rdisap and relative R velocities of disappearance and lifetime τ of faces of growing crystals have been derived for stationary growth. It was shown that the quantities are determined by the relative growth velocity RA/RcritA of the vanishing face A with respect to the critical growth velocity RcritA and by the geometry of a crystal expressed by the trigonometric functions of interfacial angles β and γ formed between face A and the adjacent faces. R increases and τ decreases with the increase in RA/RcritA to certain limiting values. The calculations have been verified and illustrated by the experimental results for triclinic potassium bichromate (KBC) crystals. Results enable ones to predict values of velocities of disappearance and lifetimes of undesirable, supplementary faces of any real crystal.
Synthesis Conditions of ZSM‐5‐Type Zeolites
Authors: Kosslick H. , Marcusson P. , Jänchen J.
Published: January 2007

Various experiments of the synthesis of chromium‐containing ZSM‐5‐type zeolites were carried out in correspondence to a cubus in the space of the variables of synthesis. By means of correlation coefficients, F‐values, stepwise multiple linear regression and cluster analysis the dependence of goal/characterization parameters on the synthesis variables were investigated. The computations show plausible explanations of the experimental results and gave additional hints which combinations of properties of the ZSM‐5‐type zeolite should be possible to design in the investigated space of synthesis conditions.
Horizontal Bridgman Growth of GaAs Doped with Isovalent Impurity
Authors: Moravec F. , Stepanek B. , Doubrava P.
Published: January 2007

Single crystals of GaAs doped with In and N were grown by the horizontal Bridgman method. The influence of isovalent doping on the crystal growth was investigated. The single crystals were examined by means of the chemical etching of dislocations, electrical measurements and optical measurements.
Measurement of Temperature Fields and Convection in an Eutectic Melt (II)
Authors: Holeček S. , Procio M. , Pražák M. , Kubíček L.
Published: January 2007

Various Types of convection have been studied in a molten AIZn Eutectic. Experiments have been conducted using a Bridgman‐Stockbarger arrangement with a furnace slid onto the specimen and moving along the specimen axis. The apparatus rotated around the horizontal axis, which made it possible to carry out measurements at different angles α contained by the gravity and temperature gradient vectors in the specimen. The amplitudes and for periodic convection also the frequencies of the temperature fluctuations have been determined.
Multicomponent Mixtures of A1 Polar Smectics with the Nematic Reentrant Phase
Authors: Ważńska Barbara
Published: January 2007

Two series of ternary systems were investigated. The first series composed of mixtures (90BCAB + 80BCAB) and 10TPCHB, the second one composed of 80BCAB and mixtures (10TPCHB + 9TPCHB). There was observed the destabilization of the smectic A1 phase followed by a nematic gap on the one side of the diagram and the extension of the smectic phase and the nematic reentrant phase on the other. The factors affecting the stability of smectic A phase and of the resulting SAd and Nre ones in these mixtures were determined.
Adsorption‐Desorption Transient Measurements of the Initial Stages of Growth of Thin Ag Films on W
Authors: Michailov E.
Published: January 2007

On the basis of precise analysis of series adsorption‐desorption transients (ADT) – registered mass‐spectrometrically (MS) around the transition points from adsorption equilibrium to real film growth, the critical parameters of phase formation process for Ag on W – coverage, impingement rate and supersaturation were estimated. It was established that the film growth starts at coverages ∼ (2.05 – 2.15) × 1015 cm−2 at hardly appreciable supersaturations, following the “Stranski‐Krastanov” (SK) growth mode – through the formation of three‐dimensional (3D) clusters on the top of complete second Ag layer.
Comparison of P‐ and B‐Contents in Si Determined by Photoluminescence (PL) at 4.2 K and 2.0 K
Authors: Schramm G.
Published: January 2007

Calibration curves to determine the concentrations of shallow impurities in Si were usually established with the help of homogeneous doped samples at 4.2 K. The improvement of the lateral resolution power necessary to characterize inhomogeneous samples can be conveniently achieved by the use of superfluid helium. The calibration curves required for it were established at 2.0 K for P‐ and B‐doped Si and compared with the dependences measured at 4.2 K. Existing differences between these curves are discussed.
Growth and Physical Characterization of Double Cation Hydrogen Double Sulphate System Li2NaH(SO4)2 · H2O
Authors: Prabaharan S. R. Sahaya , Muthusubramanian P.
Published: January 2007

Single crystals of Li2NaH(SO4)2 H2O are grown from aqueous solution, containing equimolar amounts of Li2SO4 H2O and NaHSO4 from 80°C down to 30°C over a period of 15 days, resulting in large good quality crystals. The as‐grown crystals are verified by using XRD powder technique. The local structure is discussed in the light of vibrational spectroscopy. Water of crystallization is evidenced from both IR and Raman spectra. Several endothermic and an exothermic phase transition anomalies have been observed from DTA scan. Considerable weight loss is observed at 108°C from thermogravimetric study (TGA). The melting point of the material is found to be 450 °C. The density of the compound is measured to be 2.5217 g/cm3.
Effect of Gel Parameters on Nucleation and Growth of CaSO3 · 0.5 H2O Crystals in Silica Gel
Authors: Patil S. N. , Rao A. Venkateswara
Published: January 2007

In continuation to our previous work on the gel growth of single crystals, this paper describes the effect of concentration of feed solution, gel pH, gel density, ageing of gels, intermediate neutral gel and concentration programming on nucleation and growth of CaSO3 0.5 H2O crystals. Transparent single crystals of CaSO3 0.5 H2O have been obtained at low pH and low density gels. Gel ageing and intemediate neutral gel column reduce the nucleation centres and increase the size of crystals without affecting their quality. The nucleation density increases with the increase of concentration of feed solution. By concentration programming the size of the crystals increases.
On the Fit between the Precipitates Occurring in Al–Cu and Al–Cu–Mg Alloys and the Al‐rich Matrix
Authors: Löffler H. , Siebert P. , Kroggel R. , Heyroth W.
Published: January 2007

The quality of the fit between neighbouring planes of the most important metastable phases occurring in Al–Cu and Al–Cu–Mg alloys and the Al‐rich matrix is evaluated by means of geometric models. The results obtained are compared with experimental yields.
Electron Energy Loss Spectroscopy of YBa2Cu3O7–x
Authors: Richter A. , Mahmoud S. , Kleint Ch. , Ritschel M.
Published: January 2007

Electronic excitations of Y–Ba–Cu–O polycrystalline material in superconducting form have been investigated by electron energy loss spectroscopy in reflection. The data obtained confirm recent band structure models for this material. Low electron energy losses correspond to energy levels close to the Fermi energy with an upper and lower Hubbard subband and an anionic O 2p band in the middle. Loss peaks due to interband transitions, plasmon excitations, and core electron excitations have been observed, the origin of which is interpreted by a schematic energy level diagram.
On Mechanism of Internal Stresses Formation in Electrodeposited Co‐based Alloy Films with Columnar Structure
Authors: Tochitskii T. A. , Shadrov V. G. , Boltushkin A. V.
Published: January 2007

The internal stresses formed in electrodeposited Co‐based alloy films with columnar structure have been investigated. It is shown that the sign and the value of the stresses are determined by the texture, amount of the adsorbed impurities (CoO and Co(OH)2) and character of their incorporation in the deposit. A preferable crystallite incorporation of the impurities promotes the formation of the tensile stresses through the substraction stacking faults formation. With the crystalline incorporation decreasing, the compression stresses mechanism, caused by the crystallization pressure prevails.
Comparison of Computed and Measured Temperature Distributions in the High‐pressure Liquid Encapsulated Czochralski (HPLEC) Configuration
Authors: Böttcher K. , Fuhrmann P. , Lux B. , Rauchfuss J.
Published: January 2007

The calculations of the temperature field of the InP growth system are carried out with a stationary FEM/Newton algorithm. With regard to the radiation transparency of the B2O3 layer, the limiting cases transparency and non‐transparency are investigated. With the thermocouples which are inserted into the crystal, the temporal temperature behavior at selected positions of the crystal is recorded. The shapes of the crystal/melt interface of further crystals are analysed by microscopy. Computational and experimental results agree.
A Direct Method for the Determination of Orientation Relationships Using TEM
Authors: Möck P.
Published: January 2007

A new method for the determination of orientation relationships has been developed. The method is based on a recently proposed direct method for orientation determination using a transmission electron microscope (TEM). The determination of the orientation relationship can be done by two different but generally applicable approaches. The first approach is especially applicable for crystals with orthogonal base vectors, the second approach is especially applicable for crystals with non‐orthogonal base vectors and the general bicrystal.
Phase Interaction in the Systems Sodium Selenate – Copper Selenate – Water and Sodium Selenate – Zinc Selenate – Water at 25 °C
Authors: Oykova T. , Mihov D. , Pavlova P.
Published: January 2007

The phase equilibrium in the systems Na2SeO4–CuSeO4–H2O and Na2SeO4–ZnSeO4–H2O were studied and it was established that new phases were obtained – double salts with a composition: Na2Cu(SeO4)2 · 2 H2O and Na2Zn(SeO4)2 · 2 H2O. The fields of phase equilibrium of the double salts in the triple systems were determined. The composition of the new phases was investigated by the Schreinemackers' method of physico‐chemical analysis, and the number of the water molecules of crystallization – by thermogravimetrical analysis. An X‐ray diffraction analysis of the new phases obtained was done.