bluuebunny/crossref_metadata_2025 huggingface dataset:
Nb redeposition on Si during plasma etching of Nb/SiO2/Si layers investigated by RBS
Authors: Schelle D. , Tiller H.‐J.
Published: January 2007

The redeposition of electrode material (Ni, Cr, Al) and material of a Nb layer on silicon surface during plasma etching of Nb, SiO2 and Si by a CF4 plasma has been investigated by Rutherford Back Scattering spectrometry. It is shown that a steady state

exists, what causes a Nb contamination of etched Si surfaces. Obviously this steady state concentration (Nb)ads is influenced by additional redeposition of non‐etchable electrode material as Ni, Cr and Al.
On the correlation between anisotropy of gyrotropic and magnetic properties of samarium and terbium orthoferrites
Authors: Sirota N. N. , Lomako I. D.
Published: January 2007

Rare earth orthoferrites are interesting for investigation and promising materials for practical application. This paper deals with the existence of the correlation between the polar diagrams of polarization plane rotation obtained by us (SIROTA, LOMAKO 1976, 1978, 1979) and those of magnetic torques plotted from the data of BELOV et al. 1967, 1968a, 1968b). In this case the relationship is established between the optical anisotropy and crystallographic magnetic anisotropy of the orthoferrites crystals under investigation.
Mössbauer spectra and electronic properties of titanomagnetite
Authors: Melzer K. , Šimša Z. , Łukasiak M. , Suwalski J.
Published: January 2007

Several Mössbauer studies of Ti‐Fe spinels have been reported in the literature for x ≦ 0.8 (BANERJEE et al.; VANLEERBERGHE et al.) or for x ≦ 0.05 (UMEMURA et al.). BHADURI measured the Mössbauer spectra of the whole system (0 ≦ x ≦ 1) and suggested that TixFe3−xO4 samples with x < 0.5 show the properties of delocalized electrons; whereas those with x > 0.6 may be regarded as n‐type semiconductors with localized electrons.

We present measurements of electrical properties and Mössbauer spectra of synthetic TixFe3−xO4 single crystals with x = 0; 0.24; 0.5; 0.72. It is seen that the electronic behaviour strongly depends on the content of titanium. At a composition of approximately x = 0.65 a transition from n‐ to p‐type of electrical conductivity occurs. 57Fe Mössbauer data of the samples for different temperatures obtained of the spectrum computer analysis using a least squares fit program are given. The Mössbauer spectra below and above the Néel temperature demonstrate the distinct decrease in mobility of electrons in dependence on the Ti content. It is evident from the Mössbauer spectrum of the sample Ti0.72Fe2.28O4 recorded above the Néel temperature that Titanium is incorporated into the spinel structure of this system only in a four valent state.
Investigation of the single crystal growing process of neodymium‐doped YAG garnets using radiotracers
Authors: Waliś L. , Jaskólska H. , Janusz Cz.
Published: January 2007

Radioisotopic methods of investigation of Nd behaviour during pulling of single crystals of YAG‐type garnets were applied. For the investigation of homogeneity of Nd distribution an autoradiographic method was used, and for the determination of Nd contents in single crystals and Nd effective partition ratios — techniques of radiotracers and gamma spectrometry. The conclusions from this work can find technological application.
X‐ray study of the reaction products in obtaining lead telluride by a low‐temperature iodide method
Authors: Assenov R. , Moshnikov V. , Saunin I. , Yaskov D.
Published: January 2007

Results from X‐ray studies of the products of the reaction in obtaining lead telluride by the iodide method are presented. It is demonstrated that PbI2 condenses at the flow of the inert gas on the cool parts of the reactor at the isothermal annealing of the synthesized material. This is in agreement with the assumption about the self‐alloying of PbTe as a result of the higher solubility of Pb under conditions of dissolving PbI2 in lead telluride.
Crystal growth of Mg‐ and Ti‐substituted hexagonal ferrites from PbO‐B2O3 based melts
Authors: Nevřiva Miloš
Published: January 2007

Crystals of Mg and Ti‐substituted hexaferrites have been prepared as perspective materials for the photoelectrochemical conversion of solar energy by means of anodes. The melts on the basis of PbOB2O3 were used to grow both bulk crystals and thin films. In the chosen system the primary crystallization field of hexaferrites was found. The crystals were grown by conventional unseeded crystal growth using (ACRT) accelerated crucible rotation technique to ensure their good quality and homogeneity. The size of the crystals varied from 10 to 23 mm in diameter. Maximum total content of Mg2+ and Ti4+ amounted to 2 atoms per formula unit of hexaferrite.
Low‐temperature precipitation in NaCl: Eu++ monocrystals
Authors: Suszyńska M. , Gubański A. , Opyrchal H.
Published: January 2007

It has been shown that the macroscopic features of the as grown NaCl crystals containing up to about 140 m ppm of Eu++ ions agree well with the main characteristics of the Na2EuCl4 phase present in these crystals.

Thermal decomposition of the NaCl:Eu++ solid solution leads to the formation of the mentioned Na2EuCl4 phase at temperatures not very much higher than 273 K. The kinetics of this process is governed by the pipe diffusion which leads to the growth of the small impurity aggregates already present in quenched samples.
Method for complex X‐ray diffraction analysis of TiN coatings
Authors: Valvoda V. , Černý R. , Kužel R. , Dobiášová L.
Published: January 2007

A complex of X‐ray diffraction methods for study of polycrystalline thin layers is presented. It is based on the approximation of measured profiles by suitable analytical functions. An application to TiN coatings prepared by PVD method on high‐speed steel is presented. The necessity to investigate several diffraction parameters (position, integral intensity, breadth, asymmetry) of more reflections is emphasized.
Multifrequency ultrasonic investigations in the liquid crystal 5 OCB
Authors: Gupta A. V. N. , Rao J. V. , Venkatacharyulu P.
Published: January 2007

The specific volume and ultrasonic velocity measurements (at four different fixed frequencies) are carried out in the liquid crystal 4′‐n‐pentyloxy‐4‐cyanobiphenyl (5 OCB). From these studies various physical parameters like adiabatic compressibility, molar sound velocity, molar compressibility, van der Waals' constant and intermolecular free lengths are estimated. The variation of the order parameter at the four frequencies is also studied. The results are analysed.
Crystal‐ and molecular structure of 19‐nor‐digitoxigenin
Authors: Scharfenberg‐Pfeiffer D. , Höhne E. , Wunderwald M.
Published: January 2007

19‐nor‐Digitoxigenin crystallizes in the orthorhombic space group P 212121 with four formula units C22H32O4 per unit cell. The lattice parameters are a = 7.082, b = 12.476, c = 21.486 Å. The crystal structure was determined by direct methods and refined by a least‐squares procedure to the discrepancy factor R = 0.042. — The orientation of the lactone ring relative to the steroid skeleton was found to be the opposite of that known for digitoxigenin.
Specific heats of FCC solid solutions of the Bi2O3–Er2O3 system
Authors: Berezovskaya Yu. , Budurov S. , Spasov T.
Published: January 2007

For the first time specific heats of the fcc solid solutions (Bi2O3)1−x(Er2O3)x in the temperature range 350–1000 K were measured by means of Differental Scanning Calorimetry. Samples were also investigated with thermal expansion. A possibility of tetragonal distortion with subsequent transformation in δ* phase is supposed for (Bi2O3)0.80 (Er2O3)0.20. Thermodynamic data on (Bi2O3)1−x(Er2O3)x compared with ideal solutions are discussed.
Sputter depth profiling of GaAlAs double heterostructures using auger electron spectroscopy
Authors: Chassé T. , Heichler W. , Langhammer J. , Zwanzig W.
Published: January 2007

Sputter depth profiles of GaAlAs double heterostructures had been taken by the help of Auger electron spectroscopy (AES). The sputtering ion beam consisted of either N+ — or Ar+ ions. In the case of using N+ ions an essentially better depth resolution was found comparing with Ar+ ions, especially in a sputter depth of some μm. Investigations of the sputter—crater using Scanning Electron Microscopy (SEM) and Electron Probe Micro Analysis (EPMA) showed, that the improved depth resolution during N ion sputtering is a result of the essential lowered sputter induced surface roughness. This should be caused by the stronger amorphisation of the target surface using N ions which is a consequence of the chemical reactions taking place at the surface with the sputtering ions.
Some physical properties of impurities in the Anderson model
Authors: Sedov V. L.
Published: January 2007

This paper presents the basic physical properties of impurity atoms that follow from the general form of exact solutions of the nondegenerate Anderson model. These solutions are used to study the interaction of positrons with magnetic impurities via the field of virtual plasmons.
Positron annihilation studies of binary Ni‐based alloys
Authors: Michno Z. , Gorecki T.
Published: January 2007

Positron annihilation studies of Ni–1 at. % X (X = Pb, In and Zn) alloys have been performed. The experimentally observed changes in the parameters connecting the shape of angular correlation curve with the kind and concentration of crystal lattice defects are correlated with the values of the vacancy‐solute binding energy calculated from the vacancy model of melting.
Semistatistically defected wurtzite crystal containing pairs of metal‐non‐metal vacancy
Authors: Horodecki A. J.
Published: January 2007

Basing upon the wurtzite structure the unit cell of a semistatistically defected crystal is defined as containing four unit cells of an ideal crystal and one pair of metal and non‐metal vacancy. It is shown that all of possible coordinates of these vacancies lead only to three different squares of structure amplitude. The results are used for discussion of peculiarities of X‐ray pattern of CdS thin films.
Influence of free convection on the formation of growth defects in potassium bichromate crystals grown from aqueous solutions
Authors: Szurgot M. , Sangwal K.
Published: January 2007

The influence of free convection on the formation of inclusions, growth bands and dislocations in potassium bichromate crystals grown by self‐nucleation and on freely hanging seeds from aqueous solutions in a wide range of temperature is studied. It is found that in free convection all the three types of defects appear mainly in the top sectors but in stirred solutions the slow‐growing faces are more defective.
Studies of positron annihilation at metal vacancies with two‐component positron‐electron density functional theory
Authors: Boroński E.
Published: January 2007

Recently, the fully self‐consistent two‐component density‐functional theory for electronpositron systems has been developed. The scheme is applied here in further calculations of positron annihilation in metal vacancies. In particular, angular correlation of positronelectron annihilation photons for Al vacancy is calculated and compared with conventional result. As important in some cases, the influence of self‐interaction corrections on the results is discussed. Besides, the positron binding energies to vacancies containing H and He are calculated. They are considerably different then ones obtained in one‐component approach.
A simulation of vacancy clustering in Al and its relevance to positron experiments
Authors: Usmar S. G. , He Y. , Alam A.
Published: January 2007

Preliminary results of the simulation of the vacancy clustering in Al during the quench and subsequent annealing is presented and discussed in view of their relevance to positron experiments.
Vacancy formation enthalpy in AgZn alloys
Authors: Chabik St.
Published: January 2007

Effective vacancy formation enthalpy (Hv) for AgZn alloy was determined by means of positron annihilation method. It was found that Hv decreases linearly with increasing Zn content for the α‐phase. For the ξ and β′‐phase the Hv does not change and is equal to 0.53–0.55 eV.
Positron trapping in deformed Gd
Authors: del Río J. , de Diego N. , Hidalgo C.
Published: January 2007

Positron lifetime and Doppler broadening measurements have been used to study the annealing behaviour of deformed Gd between 290 and 700 K. The observed recovery stage at about 370 K is attributed to dislocations annealing.
Positron trapping by radiation defects in metals
Authors: Ilyasov A. Z.
Published: January 2007

[Russian Text Ignored].
Crystal and molecular structure of (2–3‐η‐2‐Butyne‐1,4‐diol)‐bis‐(triphenylphosphan)‐nickel(O) Ni{[(C6H5)3P]2 (C4H6O2)}
Authors: Görls H. , Schulz B. , Rosenthal U. , Schulz W.
Published: January 2007

The crystal and molecular structure of (2–3‐η‐2‐Butyne‐1,4‐diol)‐bis‐(triphenylphosphan)‐nickel(O) has been determined by X‐ray structure analysis. It crystallizes in the tetragonal space group 14 with the cell parameters a = b = 22.277(3), and c = 15.118 (4) Å. The structure was solved by the heavy atom method and refined to R = 0.0716. The coordination geometry about the nickel atom is trigonal‐planar. Each molecule is hydrogen bonded to two neighbours. The result is an eight‐membered oxygen ring.
Crystal and molecular structure of N‐(Diethylaminothiocarbonyl)‐N′‐phenyl‐benzamidine
Authors: Braun U. , Sieler J. , Richter R. , Leban I. , Golič L.
Published: January 2007

The crystal structure of the title compound has been determined by X‐ray diffractometer data collected on a CAD‐4 diffractometer. C18H21N3S crystallizes monoclinic, space group P 21/n with a = 8.939(1) Å, b = 18.992(3) Å, c = 10.416(2) Å, β = 97.29(2) Å and Z = 4. Least‐squares refinement gave a value of R = 0.107 for 2647 observed reflections. The molecule has a configuration which can be described best by Z, E′ and exists in the tautomeric enamine form. The molecules form infinite chains connected by intermolecular N—H … S interactions, with H … S distances of 2.46 Å.
Study of the chemical reactions' influence on semiconductor films structure formation by the Monte‐Carlo method
Authors: Aleksandrov L. N. , Kogan A. N. , Bochkova R. V. , Tikhonova N. P.
Published: January 2007

The investigation by the Monte‐Carlo method of the growth of the silicon epitaxial film at a chloride CVD system has allowed to find out the composition of adsorption layer, the micromechanism of the reactions of Si atoms building‐in into the growing crystalline layer and the growth conditions influence on the growth rate and film surface roughness. The change of adsorptive layer composition in the system SiCl4—HCl—H2 (fraction of adaatoms, silicon atoms built‐in a crystal and molecules SiCl2) depending on temperature has been determined. The change of silicon film growth rate depending on temperature and concentration change of SiH2Cl2 has been established and the contribution of growth mechanism (with participation of adatom, silicon atoms and molecules SiCl2) into the total rate of film growth has been shown.
A study of the effect of depletion charge on the stable crystals structures of heavy alkalis
Authors: Radwan A. M.
Published: January 2007

In the framework of second‐order perturbation theory and model potential formalism we investigate the effect of variation of depletion charge on the prediction of stable crystal structures of K, Rb, and Cs. In the formal calculation the HCP structure is found to have the lowest energy for all three metals, even though the phonon contributions were added in case of K. Nevertheless, we were able to predict correctly the observed BCC structure by changing the sign of the depletion hole charge.
Habit, dislocation densities, and microhardness of NaClO3‐NaBrO3 mixed crystals
Authors: Hussain K. A. , Subhadra K. G. , Kishan Rao K.
Published: January 2007

Results of a systematic study of growth habit, dislocation densitics, and microhardness of the NaClO3—NaBrO3 mixed crystals are presented. A drastic change in habit of NaBrO3 for small additions of NaClO3 was observed. The composition dependence of dislocation density for this system is found to be highly non‐linear. A non‐linear composition dependence of microhardness, with positive deviations from linearity was also observed. This increase in hardness is correlated with the enhanced dislocation density in the mixed crystal.
Dielectric studies on pure and doped sr (NO3)2
Authors: Srinivas M. , Sirdeshmukh Lalitha
Published: January 2007

Single crystals of pure and Na+‐doped strontium nitrate were grown by slow evaporation of aqueous solution. Systematic measurement of dielectric constant (ϵ) and loss (tan δ) have been carried out in the frequency range of 100 Hz to 100 kHz at temperatures ranging from room temperature to 420 °C. A.C. conductivity (σ) is obtained from the data on ϵ and tan δ, ϵ, and σ were found to show anomalies around 300 °C. The results are discussed in the context of order‐disorder phase transition.
Thermo emf studies on CdTe:Sb Thin Films
Authors: Pratap K. J. , Nagabhushanam M. , Amanullah F. M. , Hari Babu V.
Published: January 2007

Thermal transport properties have been studied on as‐grown and annealed CdTe:Sb thin films of different thicknesses and concentrations of Sb. These films were prepared by sequential vacuum deposition of CdTe and Sb on clean and hot glass substrates held at 210 °C temperature at a constant rate of deposition. From these studies all the films were found to be p‐type. It is also observed that the thermoelectric power increases with Sb concentgration, thickness of the film and with annealing process.

Fermi‐energy variation with temperature have been calculated on the basis of thermo emf data. All these results have been explained on the basis of defects introduced by Sb doping.
Vacancy defects in as‐grown and nº‐irradiated GaP and GaAs1−xPx Studied by Positrons
Authors: Dlubek G. , Brümmer O. , Polity A.
Published: January 2007

Measurements of positron lifetime τ and of the shape parameter S of the Doppler‐broadened annihilation line are used to study bulk and defect properties in GaP and GaAs1−xPx. τ and S decrease linearly with the composition x of GaAs1−xPx layers. A second lifetime component (τ2 = 290 ps) observed in as‐grown GaP is attributed to stoichiometric P vacancies. After neutron irradiation of GaP and GaAs0.13P0.87 positrons are trapped by Ga vacancies (τ2 = 250 ps). These vacancies anneal out in two stages at 200–550 °C and 550–800 °C.
Electrical properties of GaAs induced by the metastability of EL2 defect
Authors: Walczak J. P. , Kaminska M. , Baranowski J. M.
Published: January 2007

Metastable properties of EL2 defect in undoped semiinsulating GaAs have been studied using photocurrent and thermally stimulated current techniques (TSC). The experimental data suggest that light induced defect reaction takes place when EL2 is transferred to its metastable state.
Crystallization kinetics of MgSO4 · 7 H2O in presence of tenside
Authors: König An. , Emons H.‐H.
Published: January 2007

The effect of sodium dodecyl sulfate (SDS) on crystallization kinetics and crystal habit of MgSO4 · 7 H2O from aqueous solutions at 25 °C was investigated in batch experiments. It highly depends on the supersaturation level. Both increasing supersaturation and rising concentration of the tenside promote the production of needle‐like crystals but the influence of the driving force is much more pronounced. SDS increases the crystallization rate and the linear crystal growth rate in length direction of the crystals. To a high degree it also influences properties of the crystallizing solution such as surface tension and viscosity.
Ultrasonic relaxation studies across N‐I transition in the liquid crystal p‐cyanophenyl trans‐4‐pentyl cyclohexane carboxylate
Authors: Venkatacharyulu P. , Gupta A. V. N. , Rao J. V.
Published: January 2007

The variation of ultrasonic velocity with temperature in the liquid crystal p‐cyanophenyl trans‐4‐pentyl cyclohexane carboxylate at four different fixed frequencies is studied. From the observed data relaxation parameters like adiabatic relaxation time, velocity at infinite frequency and velocity at zero frequency, in the vicinity of isotropic‐nematic transition are sutied. The relaxation mechanism is discussed.
Orthorhombic — tetragonal phase transition and oxygen index of YBa2Cu3O6+δ
Authors: Pietraszko A. , Wolcyrz M. , Horyń R. , Bukowski Z. , Lukaszewicz K. , Klamut J.
Published: January 2007

The orthorhombic — tetragonal phase transition of YBa2Cu3O6+δ has been investigated by X‐ray powder diffraction methods. The transition is of the second order or very close to second order and no coexistence of tetragonal and orthorhombic phases has been observed. The transition strongly depends on the oxygen index δ which changes with temperature. Typical patterns of the triplet 006, 020, and 002 obtained by precise X‐ray powder diffraction measurements have been presented and shown to be useful for identification of YBa2Cu3O6+δ and estimation of oxygen index δ.
Optical properties of helium implanted inp single crystals
Authors: Hörig W. , Orlenko V. F. , Neumann H. , Ascheron C.
Published: January 2007

Optical absorption spectra of helium implanted InP single crystals are measured in the photon energy range from 0.9 to 1.3 eV. It is found that helium implantation gives rise to exponential absorption tails below the fundamental edge. The absorption coefficients as well as the characteristic tailing energy increase with increasing fluence.
Co k‐absorption edge in some double salts
Authors: Agnihotri A. K. , Nigam A. N. , Srivastava K. S.
Published: January 2007

K edge and its EXAFS for the Co++ ion in some double salts have been recorded. The white line is the only feature that is found to be characteristic of the double salts.
X‐Ray topographic characterization of α‐Fe2O3 single crystals obtained by chemical transport with TeCl4
Authors: Vassilev I. S. , Toshev A. , Peshev P. , Botev P. A.
Published: January 2007

The method of Lang is used to study the defect structure of „as‐grown”︁ hematite crystals obtained by chemical transport with TeCl4. The presence of twin boundaries, dislocations and crystallites built in the platelet matrices is established. Considerable differences in density and distribution of the crystal disturbances are observed with samples grown under the same experimental conditions. In some cases the real structure is found to be nearly perfect.
Combined investigations of NiAl alloys by means of X‐ray photoelectron spectroscopy, compton gamma scattering and positron annihilation
Authors: Hoppe W. , Marx U. , Dlubek G. , Brümmer O.
Published: January 2007

The results of measurements of Compton profiles, photoelectron spectra, positron annihilation curves, and lifetime spectra of several NiAl alloys are discussed in terms of bonding and stability in transition metal aluminides.

The interpretation of experimental Compton profiles suggests a transfer of nearly‐free electrons from Al sites to more localized d‐like states on Ni‐sites. The transfer increases with Al contents up to 50 atomic percent. From X‐ray photoelectron spectra in the case of Al‐rich alloys a different behaviour follows. The results support a model established by Wenger. Following this in the composition range above 50 percent Al no further charge is transferred to Ni cells. The Ni d states seem to be occupied in the Al‐rich alloys. A preferential annihilation of positrons in Ni cells is though to have its origin in the enhanced negative charge of these cells caused by charge transfer.
Thermally activated de‐excitation of the EL2 metastable state in GaAs
Authors: Trautman P. , Kamińska M. , Baranowski J. M.
Published: January 2007

Measurements of absorption in the near infrared have been performed on n‐type and undoped semi‐insulating GaAs containing EL2 the main native defect in GaAs. The whole band of absorption related to EL2 disappeared after 1 μm light illumination when the crystal was cooled to helium temperatures. Measurements of the thermally activated recovery of EL2 absorption have been made. The rate of the de‐excitation is well described by the formula:

r = 1.7 · 1012 · exp (−0.36 eV/kT) + 1.6 · 10−9 · n · exp (−0.085 eV/kT) s−1 where n [cm−3] is the concentration of free electrons.
Sensivity of positron defect detection of surface layers
Authors: Arifov P. U. , Shevchenko A. V.
Published: January 2007

[Russian Text Ignore]
Positron annihilation study in Ca2+ and Sr2+‐doped KCl
Authors: Nancheva N. M. , Terzijski K. I. , Mishev P. L.
Published: January 2007

Positron lifetime and three photon annihilation measurements are reported in KCl:Ca2+ and KCl:Sr2+. The present results clearly demonstrate that the positron essentially depends on the kind of Me2+ and impurity concentration in these crystals.
Dependence of ortho‐positronium pick‐off annihilation lifetime on free volume in water‐methanol mixtures, and positronium bubble formation
Authors: Jerie K.
Published: January 2007

Sizes of free volume were quantitatively calculated for water‐methanol mixtures by means of the Kincaid and Eyring method. The results were discussed in relation to the pick‐off annihilation lifetime of ortho‐positronium in these mixtures. The existence of two ranges of methanol METH concentration in water was observed, within which the dependences of lifetime of o‐Ps annihilating by the pick‐off process τ2 on the calculated free volume size are quite different. The problem that the calculated free volume was too small for the existence of o‐Ps could be eliminated by the equilibristic formation of a bubble around o‐Ps. Correlation was shown between the free volume radii and bubble radii. The obtained results testify to the existence of the strong dependence of τ2 on the free volume radii. The peculiar shape of this dependence confirms the existence of the clathrate structure in METH‐H2O mixture.
Positron camera with high‐density avalanche chambers
Authors: Manfrass P. , Enghardt W. , Fromm W. D. , Wohlfarth D. , Hennig K.
Published: January 2007

The results of an extensive investigation of the properties of high‐density avalanche chambers (HIDAC) are presented. This study has been performed in order to optimize the layout of HIDAC dectetors, since they are intended to be applied as position sensitive detectors for annihilation radiation in a positron emission tomograph being under construction.
Wachstumsmorphologie von LiNbO3‐einkristallen bei der züchtung nach dem czochralski‐verfahren unter der einwirkung eines elektrischen feldes
Authors: Reiche P. , Bohm J. , Hermoneit B. , Rudolph P. , Schultze D.
Published: January 2007

Die Wachstumsmorphologie von Lithiumniobat‐Einkristallen, die nach der Czochralski‐Methode gezüchtet wurden, wird als Ergebnis des Wechselspiels von atomar rauhen und atomar glatten (Facetten‐) Flächen beschrieben. An glatten Flächen ist die Grenzflächenspannung zwischen Kristall und Schmelze merklich größer als an rauhen Flächen, was bei bestimmten Orientierungen der Facetten zu einer kapillaren Depression des Meniskus führen kann. Daraus resultierende hydrostatische Instabilitäten werden als Ursache für die spontane Keimbildung und Entstehung von Polykristallen angesehen.

Durch Anlegen eines elektrischen Feldes zwischen Kristall und Schmelze wird die Grenzflächenspannung verringert. Das führt unter anderem zu verbesserter Benetzung der Facetten durch die Schmelze, die Entstehung der Polykristalle wird unterdrückt.
Madelung constants of the superlattices of the laves phases
Authors: Radwan A. M.
Published: January 2007

The Madelung constants of all possible superlattices of the Laves phases are calculated using a modified form of the Ewald‐Fuchs method.
Calculation of temperature fields in a cylindrical heater system
Authors: Deus P. , John M. , Krause H. , Sauermann H.
Published: January 2007

A model for calculation of time dependent temperature fields in a cylindrical furnace used for crystal growth experiments is described. The comparison of the calculated and the experimental temperature profiles shows good agreement in the stationary case and the suitability of the model for the prediction of static temperature fields on the basis of given heating power distributions, and vice versa.
Transient regimes in the growth of large‐diameter crystals
Authors: Nalbandyan G. H. , Nemenov V. A.
Published: January 2007

The behaviour of crystallization rate and interface position under the change of Czochralski growth system parameters is theoretically and experimentally investigated for the case of large diameter crystals growth. It is shown that the large value of crystal diameter leads to the inertia and nonmonotonic character of system relaxation after the perturbation. The possibility of hesitative nonstability is discussed. The transient regimes in the growth of 30 cm diameter KCl single crystals are investigated experimentally. The behaviour of crystallization rate differs from the case of small diameter crystals and corresponds to the results of theoretical analysis.
On the morphological instability of growing crystals (I) morphological peculiarities of the transition shapes of crystals in diffusion‐controlled regime of growth
Authors: Nanev Christo N.
Published: January 2007

The shape and size of the gross morphological defect which occurs (in the form of a depression) as a result of the diffusion inhomogeneity in the matter supply on the growing crystal face with supercritical dimensions are investigated. The transition shapes of similar skeletal crystal faces are determined by considering the configuration of the steps which are moving (and accumulating) from the edge toward the centre of the crystal face. The basic parameter which is evaluated, is the width of the macroscopically flat periphery which grows around the depression and its alteration when the crystal is enlarged. The theoretical analysis is carried out by presuming that no transportation of crystallizing material occurs parallel to the crystal face. The calculations are based on the different thicknesses of the Nernst diffusion layer, a magnitude which can be easily determined experimentally by some interferometric technique, over the various regions of the growing face.
Bridgman‐stockbarger growth and spectral characteristics of Al2O3:Ti3+ single crystals
Authors: Peshev P. , Delineshev S. , Petrov V. , Manuilov N. , Yankov P. , Bachvarov I.
Published: January 2007

Single crystals of Al2O3:Ti3+ (Ti ranging from 0.1–1.5 at.%) are grown by the Bridgman‐Stockbarger method from a mixture of Al2O3 and Ti2O3 in a medium of 90% Ar and 10% H2. The radial distribution of Ti3+ in the crystals is determined by measuring the optical transmission. The absorption spectra of the crystals and the luminescence spectra of Ti3+ in the Al2O3 matrix are obtained and the crystals fluorescence lifetime is determined. The optical characteristics of the crystals have shown good agreement with the corresponding characteristics of Al2O3:Ti3+ crystals grown by other methods.
Structure refinement of paranatrolite by X‐ray diffraction
Authors: Pechar F.
Published: January 2007

Paranatrolite, Na2Al2Si3O10·3H2O, monoclinic (space group Cc), but described here the pseudo‐orthorhombic setting of Fd, with a = 18.998(3) Å, b = 19.018(3) Å, c = 6.579(2) Å, β = 90.37°(1) in analogy to scolecite. 225 parameters, including hydrogen atoms, were refined anisotropically from 1400 X‐ray diffraction reflections, the final conventional R‐value being 0.036. Tetrahedral arrangement of Si and Al are of O—D character as well as the Na+ ions. Hydrogen bonding is discussed.
Structural energetics of the intermetallic compounds CaMg2 and CaAl2
Authors: Radwan A. M.
Published: January 2007

The structures of the Laves phases CaMg2 and CaAl2 are investigated using the optimized model potential. Charge transfer, which is taken into account in an approximate and simple way, plays an important role in the determination of the stable crystal structures of both CaMg2 and CaAl2.
Radial distortions of the fermi surfaces of rubidium and cesium
Authors: Radwan A. M.
Published: January 2007

The radial distortions of the Fermi surfaces of Rb and Cs are calculated in the three principal directions 100, 110 and 111. The calculations are carried out using different values of the model potential parameters and the effective charge. Our results are compared with available experimental and theoretical ones.
Crystal structure of 4,5‐dihydro‐6‐(2‐thienyl)‐3(2H) pyridazinone azine, (C16H16N16S2)
Authors: Farag I. S. Ahmed , Kordy M. A. El , Will G.
Published: January 2007

Mr = 484, monoclinic, P 21/c, a = 5.567(1), b = 7.857(2), c = 19.194(10) Å, β = 99.97(3)°, V = 826.9 Å3, Z′ = 2, Dx = 1.43 g · cm−3, F(000) = 372, MoKα, λ = 0.71069 Å, μ = 0.328 mm−1, final R = 0.055 for 889 observed reflections, T = 293 K. The compound was prepared from a direct unusual reaction of 6‐(2‐thienyl)‐2,3,4,5‐tetrahydropyridazine‐3‐one with hydrazine hydrate. The structure was solved by direct methods and refined by full‐matrix least squares. The molecule in the solid state consists of a dimer with its two equivalent halves related by a center of symmetry at the middle of the NN bond. Each molecular fragment is nearly planar and the NN bond between the two halves is 1.296(5) Å indicating that it is a partial double bond.
The effect of temperature on the raman spectra of strontium formate dihydrate single crystals
Authors: Prieto A. C. , Rull F. , Gonzalez A. , Martin F.
Published: January 2007

The temperature dependence of the polarized Raman Spectra (3000 cm−1 – 10 cm−1, between 293 K and 10 K) of Sr(HCOO)2 · 2H2O(2D2O) and partially deuterated samples is reported. From the analysis of the internal and external modes associated with water molecules and formate ions a phase transition is deduced. This is interpreted on the basis of the positional disorder of the hydrogen atoms, situated in non‐equivalent lattice positions at low temperature.
Influence of view angle of radiation and heat of fusion on the GaAs bridgman crystal growth
Authors: Frühauf J.
Published: January 2007

The paper is concerned with the numerical simulation of temperature distributions within the ingot. The effective field of view of heat exchange by radiation depending on the difference in the radii of the ingot and furnace wall flats the axial temperature gradient in the ingot and influences the position of the solid‐liquid interface. In the vicinity of this interface the heat of fusion flats and increases the temperature gradient in the liquid and the solid respectively. Thereby the curvature of isotherms is changed, too.
Crystal and molecular structure of 14‐desoxy‐14ß‐azido‐digitoxigenin‐3‐acetate
Authors: Scharfenberg‐Pfeiffer D. , Höhne E. , Megges R. , Schmidt H.‐J.
Published: January 2007

The crystal and molecular structure of 14‐desoxy‐14ß‐azido‐digitoxigenin‐3‐acetate was determined by X‐ray analysis. The compound crystallizes in the orthorhombic space group P 212121 with four molecules C25H35N3O4 in the unit cell. The lattice parameters are a = 8.975, b = 13.698, and c = 18.958 Å. The structure was solved by direct methods and refined by least‐squares procedures up to the discrepancy factor R = 0.041.
Twinning of crystals and crystal moduli conception
Authors: Lemeshko V. V. , Obukhovsky V. V. , Rez J. S.
Published: January 2007

An idea of crystal moduli (CM) as minimum aggregates for constructing of complex crystal lattices is introduced. CM arrangement in crystals is described by means of packing groups Ĝ. Twin structure constructions are demonstrated on the base of CM conception for LiNbO3, ZnS and KTiOPO4 crystals. There are next advantages of CM conception: a) Physically not verified versions of twinning appearing in other theories (Klassen‐Nekludova; Blistanov et al. 1975, 1976a) are automatically excluded; b) CM method allows to describe crystal twinning when transition strata between twin blocks appear. The connection between CM conception and crystal growth mechanism is discussed.
An effect of oxygen pressure on the process of monocrystallization of the MnaZnbFe2O4 manganese‐zinc ferrites
Authors: Guzik E. , Fitzner K.
Published: January 2007

The present paper relates theoretical assumptions concerning the pressure of oxygen required for the process of monocrystallization of the MnaZnbFe2O4 manganese‐zinc ferrites.

A general analysis of the equilibrium diagram ZnMnFeO was carried out, taking into account the pseudobinary ZnFe2O4MnFe2O4 system for the case of the formation of the above mentioned ferrite. At the same time, it was assumed that the base material (a polycrystal) for the unidirectional solidification in a Bridgman system would be formed of two compounds, i.e.f. ZnFe2O4 and MnFe2O4.

It was stated that the monocrystallization of manganese‐zinc ferrites should be carried out in the working chamber of a furnace at a pressure of oxygen amounting to from several tenth to several megapascals, the values of these pressures depending on the composition of the crystalline phase (the values of X2, MnFe2O4 and X1, Fe2O4 used in Equation (12)).
Microstrain and lattice parameter of pure and Li2O‐doped nickel oxide solid
Authors: El‐Shabiny A. M. , El‐Shobaky G. A. , Hewaidy I. F. , Ramadan A. A.
Published: January 2007

Pure and Li2O‐doped NiO were prepared by thermal decomposition of pure and LiOH‐treated Ni(OH)2 at temperatures between 500 and 800 °C. The lattice parameter, residual microstrain and crystallite size were determined using X‐ray diffraction analyses.
Modelling of mechanism of agglomeration of KCl crystallization
Authors: Schmok K.
Published: January 2007

The article presents an analysis into agglomeration during KCl vacuum crystallization. The theoretical and experimental investigations into the mechanism of agglomeration during mass crystallization result in an extension of the growth phenomena within the known model equations. The basis for this is essentially constituted by the collision model concepts of the theory of floculation in disperse systems. The parameters derived from the microprocess analysis (energy dissipation, content of solids, growth rate of individual grains) lead to model equations which are confirmed by laboratory and test trials.
On the effect of an Si3N4 barrier layer over GaAs1−xPx during Zn diffusin: A photoluminescence analysis
Authors: Vigil E. , Zehe A. , Gracia M. , Martinez M. G.
Published: January 2007

An Si3N4 barrier layer on top of a GaAs1−xPx layer is applied to diminish the out‐diffusion of matrix atoms during the formation of p‐n junctions by Zn diffusion. An extended photoluminescence analysis of protected and nude but otherwise identical samples is carried out in order to compare the effects introduced by the barrier layers. Samples obtained from two different diffusion processes establishing the p region of a low and high impurity concentration, are studied. Spectra evolution with temperature is obtained from 10 to 300 K. Differences between spectra corresponding to samples diffused with and without an Si3N4 barrier layer indicate that nonradiative center concentrations are lowered in the presence of the barrier layer.
The influence of the terminal alkyl chain on the orientational order of solute molecules dissolved in a nematic matrix
Authors: Pelzl G. , Isenberg A. , Demus D.
Published: January 2007

The orientational order of five homologous 4‐n‐butyl 4‐n‐alkyloxyazobenzenes in the same nematic matrix has been measured. It was found that the orientational order of the solute molecules increases with increasing length of the terminal alkyl chain.
Dielectric studies on Ba(NO3)2
Authors: Srinivas M. , Sirdeshmukh Lalitha
Published: January 2007

Single crystals of Ba(NO3)2 were grown by slow evaporation of aqueous solution. The dielectric constant (ϵ) and loss (tan δ) have been measured in the frequency range of 100 Hz to 100 KHz at temperatures ranging from room temperature to 400 °C. A.c. conductivity (σ) is calculated from the data on ϵ and tan δ. ϵ, tan δ, and σ were found to show anomalies around 270 °C. The results are discussed in the light of order‐disorder phase transition.
The dependence of the surface energy of regular clusters and small crystallites on the particle size
Authors: Müller E. , Vogelsberger W. , Fritsche H.‐G.
Published: January 2007

Whereas in the case of liquids the theories on the dependence of the surface energy on the particle size are uniform in general, describing a decrease of σ with decreasing particle size, in the case of small solid particles also a dependence with the inverse sign has been assumed in the literature.

Equations of the size dependence of σ and γ are derived for icosahedral and cuboctahedral clusters of noble gases considering interactions only with next neighbours. It will be shown that the character of the size dependence is dominated by the choice of the position of the dividing surface. Compared to that, such equations are derived also for ion crystallites. The resulting differences can be explained by the differences in structure and bonding.
Oxygen potentials, stoichiometry, superconducting, and magnetic properties in the YBaCuO system
Authors: Krabbes G. , Auerswald G. , Bartl A. , Eschrig H. , Lippold B. , Ritschel M. , Vinzelberg H. , Wolf E. , Wiesner U.
Published: January 2007

The relationship between stoichiometry in YBa2Cu3Ox and oxygen potential was investigated by barometry and compared with in‐situ X‐ray diffraction experiments between 300 and 1000 °C (6 < x < 7). The physical properties are influenced even by small deviations in x. Y2BaCuO5 was included in the investigations and found to be antiferromagnetic with TN ≈ 30 K.
Investigations of curved graphite crystals for the use as X‐ray monochromators
Authors: Arnhold R. , Kauter S.
Published: January 2007

X‐ray investigations on curved graphite crystals for focusing monochromators for X‐ray powder diffractometers are performed. The reflection power, avertences of crystal blocks, and radius of curvature of these crystals were determined by measuring rocking curves in dependence on the crystal position. The favourable application of curved graphite crystals as monochromators is shown by comparative X‐ray measurements of selected reflexes.
α‐HgI2 platelets crystallization from vapour
Authors: Laskowski Jaroslav , Przyłuski Jan , Conder Kazimierz
Published: January 2007

Preparation of vapour grown platelet shaped α‐HgI2 crystals is discussed. Total pressure, temperature profile and ampoule configuration influence the yield of the process, deposition pattern, crystal shape and morphology. Growth conditions (vapour flow and surface processes) are more important for platelets formation then nucleation on the ampoule's walls. A source temperature of 150–180 °C, total pressure of 2–10 Torr at RT and horizontal configuration of the ampoule create advisable conditions for platelets growth.
Influence of impurity type on microhardness anisotropy of NaCl single crystals
Authors: Boyarskaya Yu. S. , Zhitaru R. P. , Palistrant N. A. , Linte M. A. , Terzi Z. F.
Published: January 2007

The measurements of the microhardness on the (001) and (111) face of pure and doped NaCl crystals in temperature interval 77–750 K have been performed. It is revealed that the value of II kind microhardness anisotropy, established at room temperature, is influenced by the impurity type. The change of microhardness anisotropy sign takes place at a definite temperature. It is a consequence of a different thermostability of the face under investigation.
Growth and spectroscopic characterisation of Neodymium Aluminium Barium Borate using floating zone apparatus
Authors: Kumar J. , Thirumavalavan M. , Gnanam F. D. , Ramasamy P.
Published: January 2007

Transparent Neodymium Aluminium Barium Borate (NABB) rods, 60 mm long and 5 mm in diameter, have been grown using a Floating Zone (FZ) apparatus. The preparation of sintered feed rods and growth conditions are presented. The vibrational spectra (IR and Raman) of the rods were compared with those of Neodymium Aluminium Borate (NAB) crystals grown from flux. The spectra confirmed the presence of BO3 network which had been identified to have more advantages when compared to the silicates. The absorption and the fluorescence spectra obtained for the sample demonstrates its efficiency for use as a laser material.
Representation of simulated X‐ray topographs by means of the FEAG 200 device
Authors: Härtwig J. , Witt H.‐J. , Bąk‐Misiuk J.
Published: January 2007

The photoscan and photowrite system FEAG 200 was used to represent computer simulated X‐ray section topographs. Simulated images with a high quality and with film properties similar to the real image could be obtained. Thus, theoretical images could be compared in great detail with experimental topographs.
Thermoelectric power measurements of vacuum‐deposited SnO2/Sb2O3 mixed thin films
Authors: Kumar J. Siva , Subba Rao U. V.
Published: January 2007

Thin films of various thicknesses have been prepared from the powders of [SnO2 + Sb2O3] sample by the thermal evaporation technique in the vacuum of 10−5 Torr. A jig which is convenient for the measurement of thermoelectric power on thin films in the temperature range from RT to 300 °C is designed and fabricated in our laboratory. Using the jig, thermoelectric power measurements have been made on thin films of [SnO2 + Sb2O3]. These results have shown that these thin films are n‐type in nature. The parameters like thermoactivation energy at 0 °C, temperature coefficient of activation energy, carrier concentration etc. have been calculated. The results thus obtained are presented and discussed in this paper.
A method for determination of size‐dependent crystal growth kinetics from batch experiments (II). Two‐experiment estimation
Authors: Blickle T. , Lakatos B. , Halász S. , Molnár I.
Published: January 2007

The method developed for determining size‐dependent crystal growth kinetics utilizes measurement data obtained in two batch crystallization experiments performed under the same circumstances: (1) size distribution data of the seed and product crystals of a seeded experiment and (2) the equilibrium supersaturation course of an unseeded one. In the latter case, computation is carried out in direction of reversed time thus eliminating the effect of nucleation. The evaluation makes use of the population balance equation transformed by using the assumption that the crystal growth rate is a product of two factors, the first of which depends only on the crystal size whereas the second one on the supersaturation. The application of the method is illustrated by evaluating measurement data of two appropriate experiments with potash alum crystals.
Redetermination of the crystal structure of khellin, 4,9‐dimethoxy‐7‐methyl‐5H‐furo(3,2‐g) (1)‐benzopyran, C14H12O5
Authors: El‐Kordy M. , Farag I. S. Ahmed , Will G.
Published: January 2007

The crystals of this compound are monoclinic with space group P21/n. The unit cell parameters were derived from least squares fit of the angular data for 24 high angle reflections. The lattice parameters are: a = 11.550(2), b = 7.163(1), c = 14.425(2) Å, β = 93.61(1)°, Z = 4.

The structure of this compound was solved by direct methods and refined by full matrix least‐squares with anisotropic factors to R = 0.041. The refinement of the atomic parameters reflects the planarity of the molecule in the solid state. The molecules are connected by hydrogen bonds forming a zigzag chain parallel to the [100] direction.
X‐ray diffraction study of TiN coatings sputtered at different substrate temperatures
Authors: Valvoda V. , Kužel R. , Černý R. , Dobiášová L. , Musil J. , Poulek V.
Published: January 2007

Microstructure evolution in TiN films reactively sputtered on steel substrates was investigated by X‐ray diffraction. Systematic changes of lattice parameters, texture, internal strain, and macrostress with increasing nitrogen flow into the magnetron deposition chamber were studied for the samples deposited at two different substrate temperatures (150 and 400 °C), and non‐monotonic dependences were found for all the quantities. A preferred orientation of the 〈111〉 type for substoichiometric samples is changed to the strong 〈110〉 texture at high nitrogen flow. The largest microhardness was observed for the strongly substoichiometric and very defective films. A marked anisotropy of X‐ray line broadening and lattice parameters was found for these samples. The influence of the higher substrate temperature on microstructure of the films is small for all the measured quantities at the deposition rate used (0.06–0.2 μm · min−1).