bluuebunny/crossref_metadata_2025 huggingface dataset:
Defects in LEC‐grown Indium Phosphide Crystals Doped with Tin
Authors: Wagner G. , Gottschalch V.
Published: January 2007

Crystalline defects in Sn‐doped LEC indium phosphide have been revealed by chemical etching and analyzed by TEM. Grown‐in dislocations, various kinds of defect clusters and colonies of microdefects were found. The symmetrical defect clusters are shown to equate mostly with larger dislocation loops exhibiting shear components and/or other dislocation arrangements generated by a stress source which is positioned in the centre of the dislocation cluster. Those centres are often formed by a plate‐like agglomeration composited of tiny inclusions and very small faulted dislocation loops. Such planarly arranged accumulations of microdefects lie on {111} planes. The direct vicinity of single threading grown‐in dislocations is always enriched with tiny perfect dislocation loops and precipitates. Additionally, very large isolated interstitial‐type perfect dislocation loops with b = a0/2 〈110〉 have been found by TEM experiments. Mostly, the {110} habit plane of such loops is decorated with an high number of small dislocation loops and precipitates as a consequence of dislocation climb.
Dielectric and Electrical Properties of InSe Films
Authors: Rao S. Ramchandar , Pratap K. J. , Babu V. Hari
Published: January 2007

The dielectric and electrical properties of sandwiched AlInSeAl structures of different thicknesses are investigated. For all the thicknesses the capacitance and tan δ decrease with increase in frequency. The I‐V characteristics of Al‐InSe‐Al structures have been studied for different thicknesses. These curves exhibit three regions ohmic, non‐ohmic and breakdown regions. Optical micrographs of breakdown patterns at different stages have been taken and the results are discussed.
Influence of Predeposition on the Properties of GaN
Authors: Franzheld R. , Seifert W. , Butter E.
Published: January 2007

Growth experiments with GaN in the system Ga/HCl/NH3/He or H2 were carried out in a reactor with two deposition zones. The extent of the reaction in the first zone, called the predeposition zone, is controlled by the NH3 flow rate. In the second zone GaN is deposited epitaxially onto sapphire substrates. The variation of the carrier concentration of these epilayers indicates the dominating effect of impurities especially oxygen in opposition to the widely accepted vacancy model. Due to the high incorporation ratio of donor impurities into the solid a predeposition reduces the impurity content in the vapour phase. A reduction of the free carrier concentration in the epitaxial layers could be achieved. Different behaviour in the two carrier gas systems could be established.
The Smetic Polymorphism and the Phase Transitions in the Liquid Crystal 4, n‐Hexyloxyphenyl‐4, n′‐Decyloxybenzoate
Authors: Petrov M. , Simova P.
Published: January 2007

Three different methods — microscopical, depolarized light scattering and conoscopic have been used for the investigation of the polymorphism of 4, n‐hexyloxyphenyl‐4, n′‐decyloxybenzoate (HOPDOB) at homeotropic orientation. A new textural transition is registered during cooling in smectic C phase connected with a change in the tilt (ω) and azimuthal (φ) angles of the molecular director. At cooling we found smectic E phase and by the conoscopic method we determined this phase as tilted smectic type (Et) with 24° tilt angle. It is also found that B phase is a normal type smectic liquid crystal — BN.
A Pragmatic Model for the Simulation of Self‐induced Striations in Quartz Crystals
Authors: Bernhardt Hj.
Published: January 2007

A mechanism is investigated which might lead to fluctuations in the growth of quartz crystals due to the periodic incorporation of impurities. The model ought to be applicable also to the incorporation of stoichiometric partners during the growth of complicated crystals from non‐stoichiometric melts. The processes have been simulated with help of an equivalent circuit experimentally and by computation. Some typical cases are presented in the paper.
Determination of Physical Constants of the Melt and the Parameters of the Control Object Concerning Crystal Growth from the Melt
Authors: Satunkin G. A. , Red'kin B. S. , Kurlov V. N. , Rossolenko S. N. , Tatarchenko V. A. , Tuflin Yu. A.
Published: January 2007

New Techniques are presented for the determination of the capillary constant and the coefficient of thermal expansion of the melt using an electrocontact sensor (ECS). The density of the melt, the capillary constant, the coefficient of the thermal expansion of the melt, the growth angle, and the characteristic time of thermal relaxation of the thermal zone are determined for the case of growing the lithium niobate crystals by Czochalski technique.
Crystal and Molecular Structures of Modified Progestagens (II). 17α‐Azidomethyl‐17β‐hydroxy‐cstr‐4‐en‐3‐one, C19H27N3O2
Authors: Reck G. , Hübner M. , Bohl M. , Leibnitz P.
Published: January 2007

The crystal and molecular structure of the title compound has been determined by X‐ray structure analysis. It crystallizes in the orthorhombic space group P 212121. The lattice constants are α = 9.409(2), b = 9.799(2), and c = 38.664(13) Å. The structure was solved by MULTAN‐82 and refined to R = 0.056 for 1933 observed reflections. There are two molecules, A and B, in the asymmetric unit with partly different steroid ring conformations. O17AH… O3B and O17BH… O3 A′ hydrogen bonds link the molecules into chains parallel to c.

Die Kristall‐ und Molekülstruktur der Titelverbindung wurde mit Hilfe der Röntgenkristallstrukturanalyse bestimmt. Die Verbindung kristallisiert in der orthorhombischen Raumgruppe P 212121. Die Gitterkonstanten sind a = 9.409(2), b = 9,799(2) and c = 38,664(13) Å. Die Struktur wurde mit MULTAN‐82 gelöst und bis zum R‐Wert von 0,056 für 1933 beobachtete Reflexe verfeinert. Es gibt zwei Moleküle, A und B, in der asymmetrischen Einheit mit teilweise verschiedenen Steroidkonformationen. O17H… O3B und O17BH… O3A′ Wasserstoffbrücken verbinden die Moleküle zu Ketten parallel zu c.
Structural Studies of Antimony Pentahalide Graphite Intercalation Compounds Using 001 Reflections
Authors: Ppreiss H. , Fichtner‐Schmittler H.
Published: January 2007

X‐ray diffraction studies at room temperature are reported of stages 1, 2 and 3 SbClmF5‐m graphite intercalation compounds (m = 0, 2, 4, 5). The analysis of the 001 reflection inten‐sities shows the periodic stacking of carbon, chlorine and antimony layers in all compounds. The results are in good agreement with the structural model recently found in other metal halide graphites. But we have found that the antimony atoms are not located on the mirror plane (z = O) in the centre of the intercalate layer. In case of dilute SbCl5 graphites, the identity period along c axis Ic increases with SbCl5 concentration in the stage 2 com‐pound. Interlayer distances were determined in dependence on SbCl5 concentration. A molecular layer form consisting of SbX5 molecules which are linked by halogen bridges is suggested to fill the galleries in the graphite lattice.
The Effect of Plastic Deformation on the Real Structure of ZnO Crystals during the Growth Process
Authors: Vladimirov V. I. , Kuz'mina I. P. , Loshmanov A. A. , Regel' V. R. , Sizova N. L. , Chernysheva M. A. , Kostyukov E. P. , Smirnov I. S. , Shaldin Yu. V.
Published: January 2007

The rotational model for ZnO plasticity under the action of concentraion stresses is given on the ground of the real structure analysis (the presence of two scales of the crystal lattice disorientation, a change of the ZnO crystal lattice parameter and the presence of disorientation boundaries of different types). Concentration stresses estimated at the Tgr. \documentclass{article}\pagestyle{empty}\begin{document}$ \tau = G\varepsilon = G\frac{{\Delta a}}{a} \approx 20 $\end{document} MPa exceed the yield point of crystals at Tgr. and may be the cause of rotational plasticity development.
Failure Distribution on Semiconductor Wafers
Authors: Kopelmann A. , Enders P. , Knauer A. , Bärwolff A.
Published: January 2007

Investigation of the distribution of dislocations intersecting the free surface of (1, 0, 0), Si‐doped Bridgman‐grown GaAs wafers. The defect densities were determined by using molten KOH as the defect‐revealing etch. Their distribution can well be described by the compound Poisson‐gamma distribution. The corresponding formula for the chip‐yield is derived and it is shown, under which conditions it goes over into that for the simple Poisson distribution. Further, it is shown how the finite dimension of failures can be taken into account.
Analysis of the Dynamics of the Controlled Crystallization Process Using the Czochralski Method
Authors: Satunkin G. A. , Rossolenko S. N.
Published: January 2007

A mathematical model proposed for the Czochralski method has been employed to analyse the stability, to calculate the transitional characteristics of open and closed systems for the case that the PID control is used in the feedback circuit. The method to control the crystallization process by weighing the crystal is analysed in detail. Based on the proposed criterion of quality of the transitional process, an optimum adjustment of the controller for one‐ and two‐channel control is performed.
Growth and Electron Microscopical Investigations of (CaBa)F2 Epitaxial Layers on GaAs and InP Substrates
Authors: Schumann B. , Kühn G. , Wagner G.
Published: January 2007

(CaBa)F2 layers have been grown on (100)‐oriented GaAs and InP substrates by flash evaporation technique. They were investigated by means of electron microscopical methods (RHEED, TED, TEM). Epitaxial growth was found at temperatures in the range of 725 to 825 K for GaAs substrates and 700 to 800 K for InP substrates, respectively. The films showed a fine‐grained structure and consisted of two phases always with a composition of approximately Ca0.99Ba0.01F2 and Ca0.08Ba0.92F2. This is in accordance with the occurrence of a miscibility gap observed in the binary CaF2BaF2 system.
Nucleation Studies in Supersaturated Triglycine Sulphate Solutions
Authors: Natarajan V. , Gnanam F. D. , Ramasamy P.
Published: January 2007

Rates of nucleation of supersaturated aqueous solutions of Triglycine sulphate are measured by the induction period over the temperature range 30–50 °C. The effects of temperature and supersaturation on the induction period are reported. The interfacial tension, energy of formation and radius of the critical nuclei of the crystal are calculated in accordance with classical nucleation theory. Nucleation rate increases with increase in supersaturation and temperature, while interfacial tension decreases with increase in temperature.
Secondary Nucleation of Ammonium Alum in the Presence of Insoluble Additives in the Solution
Authors: Teodossiev N.
Published: January 2007

Secondary nucleation of ammonium alum has been investigated in seeded batch crystallization from aqueous solutions. The presence of a time lag is established during which the nucleation rate increases up to a constant value. The duration of the time lag increases with increasing supersaturation. The effect of fine heteroparticles of alumina and silica on the rate of secondary nucleation is studied. The heteroparticles slightly increase the nucleation rate but cause the appearance of a considerable number of new nuclei when introduced some time after the process beginning. An assumption is made that the heteroparticles mainly affect the surviving of non‐growing nuclei without changing the actual rate of secondary nucleation.
Crystal and Molecular Structures of Modified Progestagens(III). 17α‐Chloromethyl‐17α‐hydroxy‐estr‐4‐en‐3‐one, C19H27CIO2
Authors: Reck G. , Hübner M. , Pfeiffer D.
Published: January 2007

The crystal and molecular structure of the title compound has been determined by X‐ray structure analysis. It crystallizes in the monoclinic space group P 21 with cell parameters a = 11.471(1), b = 17.261(3), c = 8.680(2) A, and β = 92.39(1) A. The structure was solved by MULTAN‐82 and refined to R = 0.067 for all 4064 reflections. There are two molecules, A and B, in the asymmetric unit with different A ring conformations. Intermolecular hydrogen bridges link the molecules into dimers.
Crystal and Molecular Structures of Modified Progestagens (IV). 17α‐Azidomethyl‐17β‐hydroxy‐estra‐4,9‐dien‐3‐one, C19H25N3O2
Authors: Reck G. , Hübner M. , Bannier G. , Scharfenberg P.
Published: January 2007

The crystal and molecular structure of 17α‐azidomethyl‐17β‐hydroxy‐estra‐4,9‐dien‐3‐one has been determined by X‐ray structure analysis. It crystallizes in the orthorhombie space group P 212121 with cell parameters a = 9.118(1), b = 9.252(1), and c = 20.444(2) Å. The structure was solved by MULTAN‐82 and refined to R = 0.042 for 1408 observed reflections. Steroid ring and 17β‐side chain conformations are discussed in the paper. Intermolecular hydrogen bridges between hydroxyl groups and carbonyl oxygen atoms link molecules forming chains in c‐direction.
Density Studies in Polymorphic Liquid Crystal N‐ (p‐n‐Heptyloxybenzylidene) p‐n‐Pentylaniline
Authors: Rao J. V. , Rao K. R. K. , Choudary L. V. , Venkatacharyulu P.
Published: January 2007

Density studies in polymorphic liquid crystal, N‐(p‐n‐heptyloxybenzylidene) p‐n‐pentyl‐aniline is carried out in isotropic liquid, nematic, smectic A, smectic C, smectic B and smectic G phases. The temperature variation of density in all the mesophases confirms that isotropic liquid to nematic, nematic to smectic A, smectic C to smectic B, smectic B to smectic G transitions are of first order while smectic A to smectic C transition is of second order. The density variation across smectic C to smectic B is greater than that of any other transition. Thermal expansion coefficients are also calculated.
Growth, Structural Characteristics and Photoelectrochemical Behaviour of Tungsten Diselenide (WSe2) Single Crystals
Authors: Prasad G. , Rao N. N. , Srivastava O. N.
Published: January 2007

Studies in regard to structural and photoelectrochemical (PEC) properties of tungsten diselenide (n‐WSe2) single crystals grown by vapour transport technique have been carried out. X‐ray diffraction (oscillation) study reveals α curious two layer lines attributable to more than one a lattice parameters coexistence of nonstoichiometric phases is thought to lead to dual α lattice parameters (3.08 Å and 2.80 Å) observed. Surface studies with optical and scanning electron microscopic techniques revealed that the crystal surfaces possess varying density of surface steps. The photoelectrochemical behaviour of n‐WSe2 electrodes examined with stepped and stepfree surfaces reveals that the steps have significant influence on the PEC behaviour. Crystals with stepfree surfaces exhibited better photoresponse as evidenced by improved photopotential (520 mV) and photocurrent density (7.5 mA/cm2). Moreover, the improved photoresponse of n‐WSe2 crystal electrodes in the present study, as compared to the previous investigation, is expected to arise from the existence of different structural phases in the as‐grown crystals (dual phases) which can lead to tandemization effect with consequent improvement in photoresponse.
Crystal and Molecular Structure of 3‐Methoxy‐estra‐1,3,5(10)‐trien‐17β‐ol
Authors: Reck Günter , Schubert Gerd , Bannier Gloria
Published: January 2007

The crystal structure determination of the title compound was undertaken to determine the conformational flexibility of the steroid skeleton. 3‐Methoxy‐estra‐1,3,5(10)‐trien‐17β‐ol (C19H26O2) crystallizes in the space group P212121 with Z = 12, a = 12.589(2), b = 16.274(5), and c = 23.535(6) Å. The structure was solved by direct methods and refined to R = 0.056. Three symmetry independent molecules having different molecular conformations were observed in the crystal. The most flexible region of the molecules is the B ring which adopts following conformations: 7α,8β‐half‐chair, 8β‐sofa, and an intermediate form between half‐chair and sofa.
Electronic Structure of [Cu(C7H4NO3S)2(H2O)4] · 2H2O Crystal
Authors: Jianmin Li , Guoqiang Pan
Published: January 2007

The electronic absorption spectrum and ESR spectrum of the crystal of the title compound [Cu(C7H4NO3S)2(H2O)4] · 2 H2O, are measured. The experimental results are discussed quantitatively by using the ligand field theory and the radial wave function of non‐free Cu(II). The electronic structure of the compound is in agreement with its crystal structure.
Effect of Buoyancy‐driven Convection on Lamellar Spacing of an AlZn Eutectic
Authors: Tuček V. , Holeček S. , Kubiček L. , Barta Č.
Published: January 2007

The influence of buoyancy‐driven convection on the lamellar spacing of an Al–Zn eutectic was studied under conditions of oriented crystallization. The convection due to buoyancy was affected by the mold position respective to the direction of action of the force of gravity. It has been found that the buoyancy‐driven convection does not exert any direct effect on the lamellar spacing. Rather, it only affects the rate of advance of the crystallization front. The lamellar spacing λ of the Al–Zn eutectic can be described as function of this rate of advance V by the relation

.
Vibrational Properties of LiGaO2 (II). Theoretical Model Considerations
Authors: Neumann H.
Published: January 2007

On the basis of the correlation method and of a simplified version of the extended Keating model with bond‐bending forces neglected sphalerite‐ and chalcopyrite‐like modes can be identified in the lattice vibration spectrum of LiGaO2. In agreement with recently published results for LiInTe2 it is found that the LiO bond is considerably weaker than the GaO bond.
Investigations of LiInSe2 Epitaxial Layers on {100}‐ and {110}‐oriented Substrates with Sphalerite Structure by Means of RHEED
Authors: Tempel A. , Schumann B. , Mitaray S. , Kühn G.
Published: January 2007

Epitaxial LiInSe2 films were deposited by flash evaporation technique on {100}, {110} GaAs and {100} GaP. By means of geometrical considerations based on the concept of corresponding substrate and deposit planes epitaxial relationships can be predicted and compared with results from reflection high energy electron diffraction (RHEED). The epitaxial relationships are given for both rhombic (β‐NaFeO2‐type) and tetragonal (chalcopyrite‐type) LiInSe2 deposits on {100}‐ and {110}‐oriented sphalerite‐type substrates.
Liquid Phase Epitaxy of SiC in the System SiTbSiC by Temperature Gradient Zone Melting (I). Investigation of Solubilities in the System SiTbSiC
Authors: Tairov Yu. M. , Peev N. S. , Smirnova N. A. , Kalnin A. A.
Published: January 2007

In the paper which is divided into three parts the liquid phase epitaxy of SiC by temperature gradient zone melting with the solvent SiTb is discussed. In the first part the solubility of SiC at different initial compositions of the SiTb solvent is studied in the temperature range 2000–2500 K.
Vickers Micromechanical Indentation Studies of Barium Oxalate Dihydrate Crystals
Authors: Dharmaprakash S. M. , Rao P. Mohan
Published: January 2007

Vickers microhardness measurements have been carried out on gel grown single crystals of barium oxalate dihydrate. The dependence of hardness on indentation load has been described. Attempts have also been made to understand the cracks developed around the micro indentation. The material chipping off and median vents observed around indentation figures have been discussed. Also explained are the fracture at high indentation load. The average load independent hardness value is 58.27 kg · mm2.
The influence of sodium chloride on the driving force of the crystallization of potassium chloride from aqueous solutions at 25 °C
Authors: König Ax. , Emons H.‐H. , Nývlt J.
Published: January 2007

Admixtures at higher concentrations affect the growth rate in two kinds by changing the kinetic phenomena and also the driving force. Based on measurements of the osmotic coefficient as a function of the total ionic strength of the solution at 25 °C different kinds of driving force are calculated. Usefull for the discussion of the admixture problem is the mean molal free enthalpy of crystallization. NaCl increases the driving force of the crystallization of KCl. It shows that the reason for the decreasing effect of NaCl in growth rate is a kinetic one.
Precipitation studies in an air‐slug crystallizer: Potash alum from aqueous solution using 2‐propanol
Authors: Halasz S. , Mullin J. W.
Published: January 2007

An air‐slug crystallizer is described and its utility demonstrated with the precipitation of potash alum from aqueous solution using 2‐propanol as the water‐miscible precipitant. Basic equipment dimensions are specified and several modes of operation explored. Best results are obtained with a controlled step‐wise addition of alcohol.
Bulk modulus — volume — ionicity relationship in tetrahedrally bonded semiconductors
Authors: Neumann H.
Published: January 2007

It is shown that the bulk modulus of all diamond, zincblende and wurtzite structure compounds can be evaluated by means of the simple relation B = b0a−m(1 – g0fi) where a is the lattice parameter, fi the spectroscopically defined bond ionicity and b0, m and g0 are constants having the same values for all compounds. This bulk modulus relation is used to estimate the bulk moduli for those zincblende and wurtzite structure compounds for which no experimental measurements have been made until now.
Observation of concentration boundary layers around growing or dissolving KH2PO4 crystals in stagnant solutions
Authors: van Enckevort W. J. P. , Matuchová M.
Published: January 2007

The solute concentration profiles around KH2PO4 crystals growing or dissoloving in stagnant aqueous solutions were studied by the schlieren method after Toepler. By this technique the thicknesses of concentration boundary layers around the crystals, formed by free convection of solution, were measured in dependence of crystal size and super (under) saturation. In the case of dissolution, theoretical estimation of the boundary layer thickness yielded a fair agreement with the observed value. For growth, the process is dominantly limited by surface kinetics, whereas volume diffusion plays a minor role.
Heat capacity of LiInS2, LiInSe2 and LiInTe2 between 200 and 550 K
Authors: Kühn G. , Pirl E. , Neumann H. , Nowak E.
Published: January 2007

The molar heat capacity at constant pressure of LiInS2, LiInSe2 and LiInTe2 was measured in the temperature range from about 200 K to 550 K. An analysis of the experimental data showed that the anharmonic contribution to the heat capacity can be described by a polynomial of fourth order in the temperature. A comparison of the results for the LiInC2VI compounds with those for the AgBIIIC2VI and AIIBIVC2V chalcopyrite compounds showed that the lattice anharmonicity effects are essentially influenced by the specific nature of the LiCVI bond.
Preparation and phase characterization of the SrCl2EuCl2 and SrCl2EuCl3 systems
Authors: Olejak‐Chodan M. , Hodorowicz S. A. , Eick H. A.
Published: January 2007

The SrCl2EuCl2 and SrCl2EuCl3 systems were investigated over the full composition ranges by the Guinier powder X‐ray diffraction technique. In the strontium chlorideeuropium dichloride system the solubility from the both ends of reactants was found when fast cooling of the melt was used. In the strontium chloride‐europium trichloride system a solid solution for the composition region up to 20 mol per cent of EuCl3 and two new intermediate chlorides, Sr4EuCl11 and Sr9Eu5Cl33, were observed. The compounds crystallize in orthorhombic symmetry with lattice parameters of 7.220(2), 35.15(1), 6.790(4) and hexagonal 12.854(4) and 24.702(8), respectively.
Influence of temperature conditions in horizontal Bridgman furnace on crystal growth of GaAs
Authors: Moravec F. , Štěpánek B.
Published: January 2007

The experimental investigation of the boat shape and boat position in the furnace in the case of unseeded horizontal Bridgman growth of GaAs single crystals was carried out. The relation between axial and radial temperature gradients in the furnace was also studied. On the basis of experimental results the optimum conditions for the growth of low dislocation density GaAs single crystals were derived.
Deformation stages in a stabilized loading cycle of fatigued FCC metals (I) experimental results
Authors: Holste C. , Kleinert W. , Fischer W.
Published: January 2007

Stabilized hysteresis loops from fatigue tests on polycrystalline nickel and on nickel monocrystals have been analysed.
About the fluorine chemistry in MCVD: The mechanism of fluorine incorporation into SiO2 layers
Authors: Kirchhof J. , Unger S. , Knappe B. , Kleinert P. , Funke A.
Published: January 2007

Fluorine incorporation during the deposition of silica layers is studied under MCVD conditions using C2F3Cl3 as fluorine source. The experimental results are compared with known models of the incorporation mechanism. It is found that a gas/solid equilibrium during the consolidation step determines the final fluorine content of the layers.
On the bindings in the elements between V and Ga(I). phase from V to Fe
Authors: Schubert K.
Published: January 2007

In the chemical elements following V with increasing column number (homologic number n) of the periodic system the second half of the 3d shell is filled, and various incident structural and physical phenomena like the SLATER‐PAULING relation request an explanation. A coherent energetical interpretation may be given by analysing the bonding types (bindings) in the various elements and related alloy phases. The bindings are described essentially by the types and commensurabilities of electron spatial correlations b and e. The correlations obey empirical crystal chemical rules allowing to infer further bindings. The analysis interprets (1) the structures of the elements considered, (2) the occurring limitations of HUND'S rule, (3) the change of the ground state magneton number P(N) at the average homologic number n = 8.2, (4) the Invar‐decrease of P at n = 8.5, (5) the structural change at n = 8.6. The last three phenomena may be interpreted by simple geometrical commensurabilities of the d‐electron correlation to the crystal structure.
About the effective temperature of crystal surfaces
Authors: Vlasov A. D.
Published: January 2007

Temperature dependences of self‐diffusion coefficients, scattered electron intensities, lattice parameters and atomic bond energies are considered. All curves representing the dependences are “splitted” into two linear ones: for a surface and for a volume of the crystal. This splitting can be eliminated and the lines representing the two linear dependences be matched, if a new variable Tc = nT (where n is a scale factor and Te is an effective temperature) is introduced. The value of n is shown to vary over not a wide range (from 1.6 to 8) for all the processes considered and in all cases n > 1. A possible physical sense of the effective temperature has been considered.
Thin silicon epitaxial layers on preannealed silicon substrates
Authors: Weidner G. , Kirscht F.‐G. , Richter F. , Seifert W. , Weidner M. , Glück B. , Mai M. , Kalmanné A. Vargha , Rausch H.
Published: January 2007

Multistep‐temperature pretreatment is used to create defect denuded zones at surfaces in conjunction with bulk defects in oxygen rich substrate wafers. Using structural etching, RF–CV measurements, EBIC investigations, and gamma spectroscopy it is shown that bulk defects act as sinks for metallic impurities being fixed at an early stage of bipolar technology, already Etchable defects induced due to subsequent processing steps – e.g., emerging from bulk regions and entering denuded zones – contain less metallic impurities. 2 μm epitaxial layers deposited on such substrates with bulk defects and denuded zones reveal excellent structural and electrical properties.
Theoretical investigation of phantom controlled crystal growth: Equations and model without surface tension
Authors: Mecseki A. , Mezo B. , Voszka R. , Galántai A. , Szabó B.
Published: January 2007

A general model with one free operator is described for growing a crystal of a given shape. We give basic equations and investigate a simple model without surface tension.
Studies on macrospiral observed in flux‐grown YAG single crystals
Authors: Thirumavalavan M. , Kumar J. , Gnanam F. D. , Ramasamy P.
Published: January 2007

Presence of spirals with unit cell dimension step height has been established over a large variety of materials. But often spirals with large step height are also being reported. In this paper such a macrospiral observed over the barium based flux grown YAG crystals is reported. Nature of this depressed spiral and growth conditions are discussed. A possible formation mechanism is suggested for the development of spiral with large step height of giant step, which is termed as macrospiral.
Slope analysis to obtain starting parameters for curve fitting calculations in the special case of the Johnson‐Mehl‐Avrami model function
Authors: Oettel W. , Fabian H.‐G.
Published: January 2007

The attempt was undertaken to describe analytically isothermal resistivity measurement curves of AlZn and AlZnMg alloys by means of the Johnson‐Mehl‐Avrami equation. The paper gives a survey of results obtained based on the application of the Extented Slope Analysis. Comparison was performed to results of fitting calculations (Linear Regression). It can be shown that the intersection behaviour after the Extented Slope Analysis leads to reasonable results if rough evaluation is required in a first stage of an investigation. Furthermore this method leads to reliable starting parameters and starting length of the fitting intervals. Additionally the second process with AlZnMg alloys can be estimated by use of the Extented Slope Analysis.
Kinetic phase diagrams of multicomponent systems
Authors: Chvoj Z.
Published: January 2007

It is derived the method of the calculation of the solidification rate and the concentration of components in the solid phase during the solidification process of the n‐component melt at the given undercooling. The calculations are performed in the framework of the stochastic theory of the kinetic phase diagrams, which were derived in the case of the steady‐state processes. This is the question of the generalization of relations derived for the binary systems.
Influence of mechanical stress on thermal oxidation phenomena of silicon
Authors: Knoll D. , Grabolla T. , Bugiel E.
Published: January 2007

Some phenomena of the thermal wet oxidation of polycrystalline silicon structures are discussed in connection with the geometry of this structures and mechanical stress present in the growing oxide layer. A model is presented considering the influence of the stress on the linear and parabolic oxidation rate constants. Basing on this model experimental results concerning the influence of oxidation parameters on the oxidepolysilicon interface structure and on closely related electrical properties can be explained.
The influence of the boundary conditions on the character of the phase transition nematic‐smectic C
Authors: Simova P. , Petrov M.
Published: January 2007

The possibility is investigated for inducing the intermediate smectic A structure in substances with nematic and smectic C phases by the boundary forces. Different geometries are used: homeotropic, homogeneous and tilted under a different angle toward the supporting substrates of the liquid crystal cell. At homeotropic and at tilted orientation where the molecules tilt toward the supporting substrates is different from the molecule tilt in the smectic layer, an intermediate smectic A structure is observed at the transition nematicsmectic C in a narrow temperature interval. In this case the phase transition nematicsmectic C extends and transforms into phase transition of second order. At homogeneous orientation and at tilted orientation of an angle equal to the molecule tilt in the smectic layer, the transition nematic‐smetic C carried out in two stages, as partially it begins on the surface still in the nematic phase and terminates at the temperature of the phase transition N‐Sc. The influence of the boundary forces depends essentially on the energy of the phase transition N‐SC of the substances.
Morphology of SiC epitaxial layers grown by temperature gradient zone melting (II). The dependence of the structural properties of the epitaxial layers on the growth conditions
Authors: Peev N. S.
Published: January 2007

In the present paper the relationships between the structural perfection of the layer, represented by the Tb average integral concentration (which is a criterion for the second phase quantity), the rocking curve half‐width (a criterion for the general structural perfection of the layer) and the layer growth conditions, represented by the quantity, which is the most important characteristic of the growth process, namely the supersaturation are discussed. The considered model allows to conclude, that a optimal value of the supersaturation exists, at which the structural perfection is maximal.
Magnetically induced rhombohedral distortion in the UxTh1−xSe and UxY1−xSe solid solutions
Authors: Palewski T. , Horn J.
Published: January 2007

Solid solutions of UxTh1−xSe for x = 1.00 ÷ 0.80 and the solid solutions of UxY1−xSe for x = 1.00 ÷ 0.60 were studied by the X‐ray diffraction over the temperature range 100 ÷ 200 K. In both systems rhombohedral distortions of the cubic rock‐salt crystal structure was observed below the Curie temperatures. The temperature and composition dependences of the rhombohedral angle ω of the rhomboedral cell and the \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{c' - a'}}{{a'}} $\end{document} ratio were determined.
A new technique for measuring thickness of thin solid films
Authors: Desai C. C.
Published: January 2007

A new technique has been developed for measuring the thickness parameter for any thin solid films. Various thin films of silver, aluminium and antimony have been prepared by using vacuum evaporation plant at the vacuum of 10−5 torr. The films have been scratched by a fine metal pin. By employing a semi‐silvered cylindrical convex lens, a point contact has been established between a silvered scratch‐film and a cylindrical lens. Multiple beam Fizeau interference fringes have been obtained over the surface of thin films. Across the step of the scratch, because of height difference, the shift in the fringes have been observed. Due to the axis of point contact, no ambiguity in allocation of ringe order has been obtained. The thicknesses of silver, aluminium and antimony thin films have been determined very precisely. The technique gives high resolution with a good degree of reproducibility and implications are discussed.
Infrared lattice vibrations in Cu2GeSe3
Authors: Riede V. , Sharif N. , Neumann H. , Sobotta H. , Omar M. S. , Pamplin B. R.
Published: January 2007

Infrared reflectivity spectra of Cu2GeSe3 are measured at room temperature in the wavenumber range from 180 to 4000 cm−1. From an analysis of the spectra the parameters of four vibrational modes are determined. The experimental results are compared with predictions from group theory. From a comparison of the results for Cu2GeSe3 with the vibrational characteristics of other chalcogenides it follows that the force constants of cation‐chalcogen bonds increase with increasing valence of the cation.
Thermal analysis of the microsegregation phenomenon in some alloys from the SbSn system
Authors: Wołczyński Waldemar , Kobylkin Artur N.
Published: January 2007

Thermal analysis in experimental verification to theoretical prediction of the maximum microsegregation phenomenon in the peritectic alloys solidification has been applied. Satisfactory agreement has been obtained between some results of theoretical calculations and experimental ones. Usibility of the DTA‐5 apparatus (original construction of the Baykov Institute of Metallurgy) to detect quite small amounts of low‐solidifying non‐equilibrium phases has been proved.
Crystallization kinetics of MgSO4 · 7 H2O at higher ranges of the driving force
Authors: König An. , König Ax. , Emons H.‐H.
Published: January 2007

By means of batch crystallization technique the crystallization kinetics of MgSO4 · 7 H2O at 25 °C at higher ranges of the supersaturation from pure aqueous solutions was investigated. It was observed that the growth rate highly depends on the habit of crystals and on their ratio of length to width, respectively. This ratio is a function of the initial supersaturation of each crystal.
Investigation of the acoustic attenuation in lead and tin tellurides obtained by the iodide method
Authors: Assenov R. , Izmailov N. V. , Moshnikov V. A. , Yaroslavtsev N. P. , Yaskov D. A.
Published: January 2007

The products of the reaction for obtaining lead telluride and tin telluride, synthesized by the iodide method, were analyzed by the method of acoustic attenuation (internal friction). The results of the investigations are in agreement with the model, suggested earlier, of self‐alloying of tellurides by metallic component.
Phase transition studies of the liquid crystal 4‐[4‐n‐hexyloxybenzylidene amino] azobenzene thermal microscopy and DSC
Authors: Rao K. R. K. , Rao J. V. , Venkatacharyulu P. , Rao S. V. Chiranjeevi , Baliah V.
Published: January 2007

The phase transition temperatures of the liquid crystal 4‐[4‐n‐hexyloxybenzylideneamino]‐azobenzene have been investigated by the thermal microscopy and the Differential Scanning Calorimetric (DSC) studies. These studies confirm that this mesogen exhibits nematic, smectic A and smectic B phases. The transition enthalpies, transition entropies and also the textures exhibited by the different phases are presented.
Growth mechanism of sodium‐cadmium formate from aqueous solution
Authors: Staroń B. , Kolasiński W.
Published: January 2007

The data on the growth rates of sodium‐cadmium formate crystal faces as a function of supersaturation in the range 0.003 < σ < 0.130 are presented and discussed. It was found that a compound growth mechanism involving volume diffusion controlled dislocation growth and mononuclear two‐dimensional nucleation can explain the data.
Texture growth and screw dislocations in smectic A phases
Authors: Morawietz K. , Demus D.
Published: January 2007

The formation of the textures of smectic A phases was investigated. In planar oriented samples the A phases grow in the shape of rods without defects. The velocity of growth is strongly anisotropic with its maximum normal to the director orientation. In non oriented samples the smectic A texture is growing in batonnets with defect structure to give focal conic textures. The maximum growth velocity of the batonnets is parallel to the director orientation. Since this would contradict to the Wulff theorem we assume a growth mechanism with a screw dislocation.
Investigation of the effect of temperature on the positron annihilation in solid and liquid tin
Authors: Rudzinska W. , Szymanski Cz. , Chabik S. , Rozenfeld B.
Published: January 2007

The temperature dependence of the counting rate, F(T), has been measured in tin. A sudden increase in the counting rate, connected with the creation of vast defects acting as positron traps, has been observed on passing through the melting point. Both the F(T) and angular correlation curves indicate that the defected areas decay with increasing temperature. The kinetics of this effect has been discussed and the vacancy formation energy, being equal to Eν = 0.50 ± 0.02 eV, has been determined.
Defect recovery after 77 K plastic deformation in bismuth
Authors: Lemahieu I. , Dorikens‐Vanpraet L. , Dorikens M. , Segers D.
Published: January 2007

Dopplerbroadening measurements were performed in 77 K deformed bismuth in the temperature range between 80 K and 410 K. An important trapping effect was observed. Two recovery stages were found, one at 230 K and the other at 380 K. The measurements were compared with the results obtained from positron annihilation lineshape measurements in as‐received polycrystalline bismuth samples of different purities, and in room temperature deformed bismuth samples. In all samples a recovery stage at 380 K was found, which is ascribed to the annealing of dislocations. Lifetime measurements were performed in the as‐received bismuth samples. For dislocations a lifetime of 289 ps was found.
Positron annihilation in thermally treated metallic glasses
Authors: Liolios An. , Dedoussis Sp. , Chardalas M. , Charalambous Ste F.
Published: January 2007

The positron lifetime dependence on the annealing temperature has been studied for two transition metal‐metalloid glasses (FeNi‐based and Co‐based). Small variations of the lifetime observed after annealing below crystallization temperature are attributed to elimination of the structural defects inherent in the as‐quenched metallic glasses. More abrupt changes at higher temperatures are ascribed to crystallization processes which lead to polycrystalline phases. Differences in positron lifetime between annealed FeNi‐based and Co‐based metallic glasses are discussed.
Positron annihilation in Co alloys containing FCC and HCP phases
Authors: Tshernyashevskii A. V. , Mikhalenkov V. S.
Published: January 2007

Positron annihilation is studied in CoCu and CoMn alloys subjected to the heat treatments which result in the structural states with various lattices, phase contents and defects concentrations. The positrons are shown to be insensitive to the hcp layers in fcc lattice which form the stacking faults. Multiple transitions through the interval of martensitic transformation initiate the formation of defects of the higher concentration the larger of the volume effect of transformation.
Study of the reversible martensitic transformation in CuZnAl alloy by positron annihilation
Authors: Panek T. J. , Plotkowski K.
Published: January 2007

The positron lifetime measurement to investigate phase transformations: martensitic phase (MP) ⇔︁ parent phase (PP) in CuZnAl alloy has been used. We have observed the generation of new defects by MP → PP transformation; these defects are liquidated by martensitic transformation. This effect is only observed in case of high concentration vacancies in alloy. In order to explain the nature of these defects we take into consideration the supervacancies idea.
Observation of precipitates in a supersaturated FeCo alloy by muon spin rotation spectroscopy: a step towards understanding embrittlement of reactor pressure vessel steels
Authors: Solt G. , Waeber W. B. , Schenck A. , Gygax F. N. , Barth S. , Frisius F.
Published: January 2007

The technique of μ+SR spectroscopy was applied to detect precipitate formation due to ageing in the binary Fe‐0.8 wt% Cu alloy. As compared to the homogenized specimen, the aged sample gives a μ+SR signal with considerably larger relaxation rate in the temperature interval 180 K <T< 350 K, having a maximum nearT= 250 K with Λ = 14 μs−1.

Since precipitation of copper plays possibly an important role in the embrittlement of neutron irradiated ferritic steels, the signal from an irradiated steel specimen has also been investigated.
On the deposition mechanism of boron in silicon CVD epitaxy
Authors: Kühne H. , Malze W.
Published: January 2007

The deposition mechanism of boron doping in CVD silicon epitaxy has been investigated by exposing silicon substrates to B2H6H2 doping gas mixtures at epitaxy temperatures and examining the effect by dopant profile measuring in an afterwards intrinsically in‐situ deposited epitaxial silicon layer. It has been shown that boron is deposited increasing its concentration on the surface linearly with prolonged exposition time and desorbed by purging the surface in pure hydrogen. In the latter case its content decreases linearly proportional to the predeposited concentration. The desorbed boron builds up a secondary doping source which maintains a parasitic boron flow for reincorporation during following layer growth.
Study of radiation damage on proton‐bombarded GaP by PIXE
Authors: Ascheron C. , Flagmeyer R. , Otto G. , Vogt J. , Frey H. U.
Published: January 2007

On GaP single crystals bombarded with 0.3 MeV and 1.0 MeV protons the fluence and depth dependences of radiation damage are studied by means of particle induced X‐ray emission spectrometry under chaneling conditions (PIXE‐C) and the Rutherford backscattering/channeling technique (RBS‐C). It is demonstrated that PIXE‐C is suitable to study depth profiles of damage density by the combination with the bevelling technique.
A research into positron annihilation of the B2F steel rolled out in step‐s with constant stretch
Authors: Liu‐Juan Zou , Cai‐Guo Zhang , Gui‐Lan Wang , Ming‐Zhong Wang
Published: January 2007

The rolling out of step‐s with constant stretch (PV‐E) is a new technology developed for rolling steel in recent years. We studied the B2F steel rolled by the new technology with the aid of the positron annihilation technique. The relationships of the average lifetime of positron annihilation with the rolling pressures, the ratio of rolling speed and the mechanical properties are obtained. The value of the lifetime shows that there are many dislocations and vacancy clusters in B2F steel after being rolled, and which are supported by observations with a transmission electronmicroscope.
Positron annihilation study of defects in martensite transformation of FeMn alloy
Authors: Yang Qian , Ruzhang Ma , Yongshu He , Maorong Huang , Shoudan Liu
Published: January 2007

It has been observed that a small number of repetitions of the transformation by thermal cycling enhanced the formation of ϵ‐Martensite whereas a large number of repetitions of transformation decreased the amount of ϵ‐Martensite formed. PAT analysis and electron microscope show that a few repetitions of the transformation produced less defects, including vacancies and dislocations, whereas a large number of repetitions of transformation produced progressively more defects. The PAT analysis also shows that these accumulated defetcs are mainly dislocations, which form a network of dislocations or a Lomer‐Cottrell dislocation net. A small number of dislocations enhanced the nucleation of ϵ‐Martensite whereas a large number of dislocations prevented the nucleation. So the dislocations‐produced by cycling transformation thermally — has a great effect on the ϵ‐formation.
An investigation on the disordered AlNiCo8 magnetic steel containing the higher Co and higher Ti by means of the positron annihilation
Authors: Juan Zou Liu , Guang‐Qu Zhu , Yuan‐Quo Chen , Cai‐Guo Zhang
Published: January 2007

In this paper, we investigate the coercive force and magnetic properties of the disordered AlNiCo8 magnetic steel containing the higher Co and higher Ti by means of the positron annihilation spectroscopy. We found that the positron annihilation lifetime τ2 is closely related to the manufacturing technique and disorientation of this steel, and which directly affect the coercive force and magnetic behavior of the material. It is also found that the microscopic constructional characteristics in the present sample are finer than the ones of the same kind sample of U.S.A. according to an analysis of the positron average life τ.
Positron lifetime study of helium clustering in Ni and Ni‐1 at.% Ti
Authors: Amarendra G. , Viswanathan B. , Gopinathan K. P.
Published: January 2007

Helium clustering and bubble growth have been studied in Ni and Ni‐1 at % Ti through positron lifetime measurements. Helium pressure in the bubble as well as bubble concentration have been estimated and compared for the cases of Ni and Ni‐1 at % Ti. The results seem to indicate enhanced helium trapping due to substitutional Ti impurity in the host Ni.
X‐ray, optical and electrical study of melt‐grown CdI2 single crystals
Authors: Nigli Selina , Jagadish C. , Chadha G. K.
Published: January 2007

CdI2 has been purified using the zone‐refining technique by giving 20 passes. Single crystals grown from the starting material showed arcing in the X‐ray oscillation photographs whereas it is absent in the crystals grown from the zone refined material. These crystals are found to be of the 4 H type. DC conductivity studies were made on these crystals at various stages of purification. The surface morphology of these crystals have been studied using an optical microscope.