bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Characterization of MBE‐grown Si/CaF2 Heterostructures
Authors: Rossek U. , Mäder M. , Tempel A. 
Published: January 2007

AbstractGrowth and fabrication of silicon‐on‐insulator structures, based on heteroepitaxial growth of insulating films on Si, is an area of research that has rapidly developed in recent years. Thin CaF2 films and Si/CaF2 multilayers were prepared on {111}‐oriented Si substrates by molecular beam epitaxy (MBE) and were investigated by RHEED and RBS. For epitaxial growth the Si substrates were cleaned using the ultraviolet/ozone surface cleaning method which is an effective tool to remove contaminants from the surface by low‐temperature in‐vacuo preheating. The growth of CaF2 on such Si{111} substrates provides epitaxial layers with a high structural perfection. When this layer system, however, is used as a substrate for epitaxial Si growth the Si layers show always twin formation. Si layers without twins could be obtained only after deposition of thin amorphous Si buffer layers at room temperature, immediately followed by Si growth at 700 °C.
Hard Heteroepitaxy on 2° Off‐oriented GaAs (100) Substrates (I). The Occurrence of (100) and (111) Surface Orientations in MBE‐grown PbTe Films
Authors: Sadowski J. , Dynowska E. , Regiński K. , Herman M. A. 
Published: January 2007

AbstractThe MBE growth of PbTe layers on GaAs (100) 2° off‐oriented substrates belongs to hard heteroepitaxy, because the two materials differ strongly in their lattice constants and, in addition, they also exhibit different crystal structures. Consequently, phases with different surface orientations may occur in MBE‐grown PbTe epilayers. Two crystallographic orientations, i.e. (100) and (111), have been found in the PbTe epilayers grown by MBE on these off‐oriented substrates. X‐ray diffraction and reflection high energy electron diffraction (RHEED) measurements applied as post growth characterization techniques allow to identify which orientation is prevailing in films grown at different MBE conditions. It has been shown that the occurrence of the (100) and (111) orientations in MBE‐grown PbTe epilayers depends mainly on the GaAs substrate in situ preheating procedure. At higher preheating temperature and longer preheating time the (111) orientation prevails. This finding is in accordance with the theoretical model of hard heteroepitaxy of CdTe on GaAs (100) substrates by Griesche et al.
On Formation of Corrosion Products in Sanitary Pipes
Authors: Wollmann M. , Jacobi H. , Follner H. 
Published: January 2007

AbstractIn copper pipework, at work for about four years, blue coloured striations or areas, mainly composed of posnjakite (Cu4(OH)6SO4 · H2O), were found (water chemistry (room temperature): pH = 8.1; SO4 = 24 mg/l; Cl = 16 mg/l; O2 = 10 mg/l). Moreover cuprite, tenorite and malachite were detected on the internal surfaces of copper pipeworks. After the pipework had been in operation for five years, an NaHCO3‐dosing apparatus was installed to treat water in all but one branch of the system. In the section with treated water, sulphate formation decreased while malachite formation (Cu2CO3(OH)2) increased. Layer formation can be simulated in electroysis experiments. Normal tap water alone or mixed with bicarbonate is used as an electrolyte.
DSC Transformation Behaviour of a bcc Mg11Sm Phase Prepared by Rapid Solidification
Authors: Budurov Stojan , Zolova Genka 
Published: January 2007

AbstractThe transformation behaviour of the bcc Mg11Sm phase prepared by rapid solidification from the melt has been studied by DSC. The Kissinger and Ozawa equations led to the following activation energies of the first and the second phase transition: E ≈ 130 kJ/mol and E ≈ 194 kJ/mol, respectively. Isothermal Avrami kinetics of the first phase transition starts with an Avrami exponent n ≈ 2,5, dropping down at higher degrees of transformation to n ≈ 1.5. The data obtained have been compared with the parameters of the isothermal Avrami kinetics of decomposition of a rapidly quenched supersaturated MgYb4.87 alloy.
Influence of pH on the Crystal Size Distribution of Mg(OH)2 Prepared by the Hydration of MgO
Authors: Láska M. , Valtýni J. , Fellner P. 
Published: January 2007

AbstractThe effect of pH and temperature of aqueous solution on hydration of MgO in a batch laboratory reactor was investigated. The experiments were carried out at the temperatures of 120 and 140 °C, pH of cool solution was changed from 10 to 13. It was found that even a small amount of added base substance influences remarkably the size of Mg(OH)2 crystals. Increasing of pH of aqueous environment of causes the decrease of the size of crystals. The increase of the temperature increase dimensions (L50) of crystals. This effect is more important at higher alkalinity of the solution.
The Real Structure of Ge Ions‐implanted Si Crystals Subjected to Thermal Annealing
Authors: Auleytner J. , Adamczewska J. , Reginński K. 
Published: January 2007

AbstractIn the experiment an (111) oriented silicon plate was subjected to implantation by 80 keV Ge ions. Then, the thermal annealing of this sample was carried out in a vacuum of 5 · 10−8 Tr. The effectiveness of the annealing has been analyzed by means of X‐ray topography, double crystal X‐ray spectrometry and reflection high energy electron diffraction. The rocking curves in reflection and transmission as well as changes in anomalous absorption coefficient were measured. The results have been compared with effects of pulsed‐laser annealing investigated by AULEYTNER et al. an thermal annealing (PRUSSIN).
Influence of the Substrate Hardness on the Validity of Bückle's Rule
Authors: Berg Gunnar , Grau Peter 
Published: January 2007

AbstractGenerally the substrate hardness of a coated sample influences the measured compound hardness also for small penetration depths. But there exists the empirical rule (Bückle) that for small penetration depths this influence can be neglected. This should be right for values smaller than 1/10 of the film thickness with the limits 1/7 and 1/14. Bückle accentuates the equivalence of the rule for soft films on hard substrates and hard films on soft substrates, respectively.The possibility is shown that the compound hardness can be estimated from film and substrate hardness by an interpolation formula without any suggestions with respect of the depth dependence of the hardness of the two materials. By means of this formula one can show that the mentioned Bückle rule is not generally valid. Only for soft films on hard substrates one can estimate a noticeably Bückle region useful to measure the film hardness directly for penetration depths up to about 1/10 of the film thickness.
A Mechanism of High‐Tc Superconductivity Relating to Perovskite Crystal Structure
Authors: Wang Y. S. , Bennema P. , Zheng M. N. , Fu C. M. , van der Linden P. 
Published: January 2007

AbstractA mechanism of high‐Tc superconductivity related to the perovskite crystal structure is proposed by a “phonon attenuation model”, which means that in the perovskite‐like crystal structure, a number of “ordering” vacancies or holes occur due to the non‐stoichiometric structure features. Such a reticular “spongly‐like” structure facilitates lattice thermovibration attenuation perovskite (phonon attenuation) during temperature reduction. This leads to an abrupt drop of the resistivity, owing to the conduction electrons transmitted through the media without collision with irregularities in the lattice due to the lattice thermovibration. This probably is the main reason for high‐Tc superconductivity of the perovskite cuprates.
Electric Field‐Induced Phase Transitions in Electro‐Optic Cell with Dielectrically Negative Chiral Nematic Liquid Crystal
Authors: Pirkl S. 
Published: January 2007

AbstractBehaviour of a chiral nematic mixture with a negative dielectric anisotropy was studied between two electrodes with homeotropic anchoring in the presence of an a.c. electric field. By changing the sample thicknessdand field strengthEat constant cholesteric pitchp, the phase diagram in the parameter plane (d/p, E) was determined. Usefullness of this diagram for realization of positive contrast dichroic LC displays with nematic‐cholesteric phase change is discussed.
Control of Nucleation in Gel by GNGT — II
Authors: Sivanesan G. , Pandian S. Selvasekara , Gnanam F. D. 
Published: January 2007

AbstractThe Graded Neutral Gel Technique (GNGT) of controlling the nucleation was extended to the gel growth of crystals by a solubility reduction process. Successful and interesting results were obtained in five systems, of the six tried. Attainment of morphological stability, growth around the axial region, and elimination of the growth of pseudo‐structures and salting out effect were the salient features observed.
On Mechanism of Oxide Formation in Electrodeposited Co‐based Films with Columnar Structure
Authors: Tochitskii T. A. , Shadrov V. G. , Boltushkin A. V. 
Published: January 2007

AbstractAn investigation of the Co oxides formation and distribution dependent on preparation conditions during electrodeposition of hcp Co‐based films with perpendicular magnetic anisotropy has been made. It has been shown that the [100] oriented columnar crystallites promote some regularity in impurity distribution and orientation in the film plane, whereas the [001] oriented ones‐ non‐regular distribution. Such a behaviour is associated with the difference in the impurity incorporation for these two cases: preferably crystalline and intergranular, respectively, and atomic bonds saturation, and influence on the mechanical and magnetic properties of the investigated films.
Ferroelectric PbTiO3 Powders and Thin Films Derived from Sol‐Gel Processing
Authors: Cho C. R. , Jang M. S. , Jeong S. Y. , Kim Y. B. 
Published: January 2007

AbstractLead titanate powders and thin films were prepared by the sol‐gel process of metal alkoxide solutions and solvents. From DSC measurements, phase transition temperature of crystallized PbTiO3 powders was obtained at about 484 °C. From XRD investigation, it was confirmed that the tetragonal phase of polycrystalline PbTiO3 thin films is formed by coating of concentrated solution on all of the substrates we used after heat treatment above 500 °C.It was found by SEM and ellipsometric analysis that the thin film coated with 0.25 M concentrated solutions once had an average thickness of about 720 Å. Surfaces of thin films were crack‐free, uniform, and its average grain size investigated by SEM was 0.6–0.8 μm. Band gap energy of PbTiO3 thin film coated on the Al2O3 (2243) substrate was 3.45 eV, which is assumed to be due to the direct band to band transition. Dielectric constant (ϵ) and dielectric loss (tan δ) of PbTiO3 thin film amounted to 60–70 and 0.01–0.02 in the region of 10 kHz ∼ 1 MHz at room temperature, respectively, and transition temperature was 486 °C at 1 MHz. From the hysteresis loop of PbTiO3 thin film, spontaneous polarization of 12 μC/cm2 and coercive filed of 45 kV/cm were obtained.
On Texture Formation at Cold Rolling of Mn‐Cu Alloys
Authors: Demin S. A. 
Published: January 2007

AbstractThe texture formation in quenched γ‐phase Mn‐Cu alloys at cold rolling have been studied. It was found that the final texture in martensitic Mn‐10% Cu alloy consists of nearly equal volume of {001}〈100〉 and {112}〈111〉 texture components. A sharper {101}〈121〉 component in small amounts can be present too. In austenitic Mn‐22% Cu alloy the {112}〈111〉 component is more scattered and weakened, and the strong {101}〈121〉 component has formed. In the Mn‐30% Cu alloy the {001}〈100〉 component is almost absent, {112}〈111〉 is very weak and the {101}〈121〉 texture is dominated.
X‐Ray Studies of Some Europium Compounds at Elevated Temperatures
Authors: Hussain K. A. , Sirdeshmukh D. B. 
Published: January 2007

AbstractThe temperature variation of the lattice constants of europium iron garnet (Eu3Fe5O12), europium sulphide (EuS) and europium fluoride (EuF2) has been studied using an X‐ray powder diffractometer. The lattice constant of Eu3Fe5O12 increases linearly upto 800 °C with an expansion coefficient of 10.4 × 10−6 °C−1. In the case of EuS, the lattice constant increases non‐linearly with temperature. At room temperature the expansion coefficient has a value of 14.3 × 10−6 °C−1. In EuF2 the lattice constant increases non‐linearly upto 140 °C. At higher temperatures, the lattice constant decreases with increasing temperature with a negative expansion coefficient of −29 × 10−6 °C−1 over the range 170–235 °C. The cause of the anomalous behaviour observed in EuF2 is yet to be understood.
Effect of Thermal Treatment and Sweeping on the Electrical Conductivity of Quartz Crystals
Authors: Iliescu B. , Topa V. , Tanase A. T. 
Published: January 2007

AbstractThe effect of thermal treatment and sweeping at different temperatures on the current peaks occurring during the heating‐up phase of the electrodiffusion runs are studied. Arrhenius plots of swept synthetic quartz are discussed.
Doping of GaSb single crystals with volatile elements
Authors: Štěpánek B. , Šestáková V. , Krištofik J. 
Published: January 2007

AbstractThe Czochralski technique without encapsulant in a flowing atmosphere of hydrogen was used for the growth of GaSb single crystals doped with either sulphur or nitrogen. It has been shown that this method is not suitable for the prepartion of GaSb doped with volatile elements because they evaporate during the growth procedure and impair the single crystalline growth. The highest concentration of sulphur in the single crystals has been found to be < 1.2 × 1017 atoms · cm−3. At higher concentrations, GaSb became either polycrystalline or twinned. The growth of N‐doped single crystals was similar to that of S‐doped GaSb.
Highly homogeneous polycrystalline HgTe synthesis under pressure
Authors: Lazarescu M. F. , Manea A. S. 
Published: January 2007

AbstractA high pressure technique for the direct synthesis of polycrystalline HgTe in quartz ampoules is presented. An excess of mercury as well as a quasi‐static regime of the inert gas pressure at melt temperatures up to 750°C have been used. X‐ray diffraction and SEM confirmed the structural homogeneity of the synthesized material.
Simulation of dopant zone‐leveling in a solid ingot
Authors: Cywiński R. , Damm J. Z. , Poźniak J. 
Published: January 2007

AbstractSimple simulation procedure permitting to perform accurate calculations of the dopant distribution in an ingot after desired number of passes of the molten zone is presented. The results obtained for various distribution coefficients and various widths of the molten zone are discussed. It is shown that the number of passes indispensable for the dopant concentration leveling drastically decreases with the width of the molten zone even for the most disadvantageous range of the distribution coefficients.
Detection of side‐products on heavy metal cations loaded zeolites by XRD measurements
Authors: Steinike U. , Lutz W. , Wark M. , Jancke K. 
Published: January 2007

AbstractDuring the high loading of A, X, and Y zeolites with heavy metal cations by ion‐exchange undesired hydroxides are formed at the crystal surface. The precipitation is caused by the alkaline reaction of the parent sodium modification of zeolites in aqueous solutions and the low solubility product of heavy metal hydroxides. During the calcination of the samples the hydroxides are transformed into oxides. Exemplified by zeolite ZnNaA, a stepwise exchange in strongly diluted salt solutions may hinder the formation of hydroxides/oxides. XRD measurements enable a direct monitoring also of smallest amounts of zinc hydroxide/zinc oxide. The framework adopted ZnO causes a change of the symmetry of the zeolite lattice. The side product does not influence the formation of the new crystalline phases during the calcination of ZnNaA.
Dislocations in synthetic quartz
Authors: Chirilǎ R. , Iliescu B. 
Published: January 2007

AbstractThe present paper is a review of the data about the dislocations in the as‐grown quartz crystal. The work presents some general considerations about dislocations, their origins and causes, methods of their observation and techniques to reduce the dislocations density. It is also shown a method to obtain a new shape crystal used in the positive X‐seeds preparation.
Vertical Bridgman growth and optical properties of doped Bi12SiO20 crystals
Authors: Xuewu Xu , Jingying Liao , Bingfu Shen , Peifa Shao , Chongfan He 
Published: January 2007

AbstractThe core‐free BSO crystals with high optical quality, doped with NiO, Sb2O3, V2O5, Nb2O5, Ta2O5, and P2O5, have been grown by the vertical Bridgman (VB) method for the first time. The “interface” segregation coefficients of the above‐mentioned dopants in BSO with values of 0.014, 0.162, 0.704, 0.039, 0.077, and 0.976, respectively, have been approximately evaluated according to the diffusive solute transport regime with the assumption of negligible natural convection in the melt. The transmission spectra of various doped BSO crystals have been measured in the range from 300 to 700 nm. A blue shift of the transmission edge in Ni‐, Sb‐, and P‐doped BSO and a red shift in Nb‐ and V‐doped BSO have been found as compared to undoped BSO. The modification in the absorption amplitude implies that the photorefractive performances of BSO crystals may be improved through doping.
The emission and structure of a new laser crystal Nd3+: NaY(WO4)2
Authors: Yizong He , Guofu Wang , Xiaoying Huang , Zundu Luo 
Published: January 2007

AbstractA new laser Nd3+ : NaY(WO4)2 crystal rod of Φ 2.5 × 5 mm was pumped by a xenon flash lamp, and a 1.06 μm laser output was for the first time obtained in our laboratory, which has a threshold lower than 1 J. The crystal structure of NaY(WO4)2 was determined. The crystal is tetragonal, with the space group 141/a, a = 5.205(2) Å, c = 11.251(3) Å, V = 304.8(2) Å3, Z = 2, Dcalc = 6.62 g/cm3, Dobs = 6.51 g/cm3.
EPR study of divalent manganese in northupite single crystal
Authors: Eftaxias K. , Vassilikou‐Dova A. B. 
Published: January 2007

AbstractEPR spectra of Mn2+ in northupite single crystals were measured at X‐band and room temperature. Only one isotropic sextet is recorded for all orientations. The hyperfine splitting constant of 81 · 10−4 cm−1 is in the expected range for Mn2+ in six‐fold coordination. The very small zero field splitting gives a strong evidence that the occupied site by Mn‐ion is the Mg‐site in consistence with the preference of Mn2+ for such a substitution.
Infrared lattice vibrations of PbGa2S4
Authors: Neumann H. , Sobotta H. , Syrbu N. N. , Golovei V. M. 
Published: January 2007

AbstractInfrared reflectivity spectra of PbGa2S4 single crystals are measured at room temperature in the wavenumber range from 30 to 4000 cm−1 for the polarization directions E ∥ c and E ∥ b. The frequencies of 13 B1u modes and 11 B2u modes are derived from the spectra. The results are compared with previous studies and with lattice vibration data of ternary chalcopyrite and defect‐chalcopyrite compounds.
Growth of dysprosium garnet single crystals with spiral shape using Czochralski technique
Authors: Kimura H. , Numazawa T. , Sato M. , Maeda H. 
Published: January 2007

AbstractThe growth conditions of dysprosium garnets single crystals, to obtain a long and good spiral shape crystal, have been investigated using the conventional Czochralski technique along the [111] pulling direction. The good spiral shape of Dy3Ga5O12 single crystal with 40 mm in length is grown with its spiral pitch and spiral diameter of 20 mm and 15 mm, respectively.
Temperature dependence of grain growth in zone‐refined tin containing large additions of zinc in solid solution
Authors: Fawzy A. , Youssef S. B. , Beshai M. H. N. , Saad G. 
Published: January 2007

AbstractGrain growth in zone‐refined tin containing high concentrations > 0.05 < 0.40 wt% Zn in solid solution have been investigated in the temperature range 70–160°C. It has been found that increasing the zinc content by a factor of 8 decreased the rate of grain growth by ∼ 30% at all annealing temperatures, and this was attributed to small variations of grain boundary mobility. In addition, the increase of annealing temperature from 70 to 160°C resulted in the increase of grain growth by a factor of ∼ 50 at any given concentration, which shows that the rate of grain growth is not strongly influenced by increasing the zinc concentration. The energy activating the growth process was calculated for all concentrations investigated and had a nearly constant value of ∼ 1 eV. An empirical formula was proposed relating the rate of grain growth and the solute concentration.
Free space crystallography and the volume term of Gibbs energy in heptagon patterns
Authors: Leuschner D. , Leuschner Chr. , Leuschner C. 
Published: January 2007

AbstractGaps or free space are studied in heptagon patterns. Geometrical features of 2‐D nets are investigated. The volume terms of Gibbs energy in corresponding 3‐D lattices is estimated. The importance of the research of gaps and space filling is confirmed by the study of the FSCSC (free space crystallography of strange crystals) row of three heptagon patterns with the interesting number (per unit cell) sequences (heptagons: 4, 6, 8; gaps: 2, 3, 4) represented here.
X‐ray crystal structure analysis of parthenin–A sesquiterpene lactone
Authors: Gupta Vivek K. , Goswami K. N. , Bhutani K. K. 
Published: January 2007

AbstractThe crystal structure of parthenin has been determined by X‐ray structure analysis. The compound crystallizes in the tetragonal space group P41 with cell parameters a = b = 6.8677(2), c = 28.6851(4) Å. The structure has been solved by direct methods and refined to R = 0.039. The seven‐membered ring assumes a chair conformation while the two five‐membered rings have envelope shapes. The A/B and B/C junctions are trans. Molecules are held together by hydrogen bonds.
Influence of carbon contamination on etched GaSb substrate on the quality of MBE‐GaSb film and electrical transport through the film and the substrate
Authors: Kodama M. 
Published: January 2007

AbstractUndoped MBE‐GaSb films were grown on undoped GaSb (100) substrates and the influence of carbon contamination on the etched GaSb substrate on the grown film were investigated. It was found that carbon contamination of the etched GaSb substrate was dependent on the chemical treatment method and produced stacking faults in the subsequent MBE growth of the GaSb film. Carbon contamination on the etched GaSb substrate degraded the quality of the GaSb film and affected ohmic characteristics between the film and the substrate. Substrate surface free of carbon contamination and thereby exhibitting no influence on the electrical transport through the film and the substrate could be reproducibly obtained by performing an oxide etch‐off chemical treatment on the GaSb substrate.
Measurement of supersaturation
Authors: Nývlt J. , Karel M. , Písařík S. 
Published: January 2007

AbstractThe supersaturation of aqueous solutions of potash alum during a batch crystallization experiment has been determined by means of conductometry and refractometry. The results of both of the methods can be compared satisfactorily, but under the given conditions of home‐made equipment the refractometric determination seems to be more reliable.
Influence of proton implantation on the properties of CuInSe2single crystals (II)
Authors: Yakushev M. V. , Neumann H. , Tomlinson R. D. , Rimmer P. , Lippold G. 
Published: January 2007

AbstractCopper deficient p‐type conducting CuInSe2single crystals were implanted with 40 keV protons in the fluence range from 2.5 · 1014to 1.5 · 1016cm−2. Over the whole fluence range the implanted layers were n‐type conducting which is ascribed to passivation of the acceptors due to copper vacancies and formation of donors by hydrogen atoms located at interstitial positions. The thermal stability of the conductivity changes due to proton implantation is limited to temperatures below 100 °C.