bluuebunny/crossref_metadata_2025_split huggingface dataset:
About the Reliability of Approximate Methods for Analysing Photoreflectance Spectra of Semiconductors
Authors: Neumann H. , Bouamama Kh. 
Published: January 2007

AbstractThe approximate relation for photoreflectance spectra in the limit of weak electric fields and both correct and approximate relations for photoreflectance spectra for intermediate uniform electric fields are compared with spectra calculated with the integral method accounting for the spatial dependence of the electric field within the near‐surface space charge region of the semicondcctor. From numerical calculations performed for n‐type GaAs it follows that rather accurate critical point energies and surface electric fields are obtained provided that the width of the space charge layer is comparable with or larger than the absorption length. Sufficiently reliable values for the broadening energy of the spectra and for the light‐induced modulation of the surface electric field can only be achieved if the correct relation for photoreflectance spectra for uniform electric fields is used to analyse the Franz‐Keldysh oscillations.
Thermoluminescence and Optical Absorption Studies of Z1 Centers in KCI Crystals Doped with Praseodymium
Authors: Balraj K. , Veeresham P. 
Published: January 2007

AbstractThermoluminescence (TL) of Pr‐doped KCI is studied. The influence of pre‐heat treatment and optical bleaching of the glow curves and the production of Z1 centers are discussed. The glow curves of KCI containing 1062 ppm of praseodymium (Pr) shows one shoulder at 365 K (T1) and two peaks around 408 K (T2) and 443 K (T3), respectively. Bleaching of X‐irradiated crystals shows that the peak T2 is enhanced whereas other two (T1, T3) get suppressed. Optical absorption studies of the crystals before and after F‐bleaching shows that the F‐band decreases and shifts towards longer wavelengths. The decrease is accompanied by broadening towards the longer wavelength. The T2 peak is attributed to Z1 centres. It is shown that T1 corresponds to shallow centers and T3 peak is attributed to F‐centers.
Controls on Morphology of Analcime‐Pollucite in Natural Minerals, Synthetic Phases, and Nuclear Waste Products
Authors: Teertstra D. K. , Černý P. 
Published: January 2007

AbstractCrystals of the analcime‐pollucite series (NaAlSi2O6 · H2OCsAlSi2O6) exhibit tetragon‐trioctahedral {211} and hexahedral {100} morphology, with rare modification by tetrahexahedral {210} or rhombic dodecahedral {110} forms. Under weakly acidic to weakly basic conditions {100} is dominant; with increasing alkalinity (cation concentration), basicity (pH), and temperature {211} is dominant over {100}, with minor development of {210}. The morphology does not appear to be influenced by broad ranges in Si/Al (from 2.0 to 2.6 in the natural minerals) and Na‐Cs contents between analcime and pollucite, by substitutions of univalent cations Li, K, Rb, and Tl, or by small amounts of divalent cations Mg, Mn, Ni, Zn, Fe. Larger amounts of Ca, however, and possible substitutions for framework Al and Si seem to produce a more complex morphology.
Verification and Application of Modified Kick's Law to Rhombohedral Crystals: Sodium Nitrate
Authors: Joshi D. R. , Pandya J. R. 
Published: January 2007

AbstractOptical study of mechanical response indicated by Knoop indentation of cleavage faces of synthetic sodium nitrate crystal based on MEYER's Law/KICK's Law (P = adn) and also on modified KICK's Law {(P — W) = bd2} expressing relations between applied load P and diagonal length d is made. The Newtonian resistance pressure W is finite and positive. The value of standard hardness (a and b), exponent n are calculated. It is found that W and b are almost contant and independent of thermal treatment and of the indenter orientation with respect to direction [100] on cleavage plane (100) of sodium nitrate crystals. Since they are independent of indenter orientations, they are not associated with crystal anisotropy.
Thermoelectric Phenomena in Gallium Monosulphide Single Crystals
Authors: Gamal G. A. , Nassary M. M. , Hussein S. A. 
Published: January 2007

AbstractMeasurements of thermoelectric power of GaS single crystals grown by melt growth technique, were performed in the range of 150 K to 500 K. Investigations of GaS compound have revealed that it has interesting properties. Many physical parameters were determined such as carriers mobilities, effective masses of free charge carriers, diffusion coefficient and diffusion length as well as the relaxation time. Also the thermoelectric power behaviour showed the p‐type nature of GaS crystals.
Kinetic Investigations within the Transition Region from Polyhedral to Skeletal Growth Mode (V). Growth Kinetics of the Pyramidal Face of Zinc Single Crystals under Diffusion Conditions
Authors: Iwanov D. 
Published: January 2007

AbstractThe growth kinetics of the pyramidal face of zinc single crystals is studied in the presence of argon. The curves size vs. time provide evidence that smaller crystals grow in a kinetic regime and after reaching a certain critical size their growth continues in a diffusion regime. The growth kinetics of faces {101} and {0001} are compared. It is established that the growth of both faces simultaneously changes from a kinetic to a diffusion growth mode. During the transition between the two regimes, however, loss of the morphological stability only of the smooth {0001} face is observed, while the {101} face with macro steps formed on the surface acquires a skeletal shape after prolonged growth. It is shown that the appearance of morphological instability depends on the surface structure of the crystal faces.
The Mechanism as SI GaAs Substrate Influences the Resistivity of the Epitaxial Layer
Authors: Somogyi K. 
Published: January 2007

AbstractIt is known that it is possible to grow a semi‐insulating or, at least, a high resistivity GaAs epitaxial layer without doping on an SI GaAs substrate by VPE. The SI substrate is suspected as the originator of the high resistivity intermediate layer and diffusion and/or out‐diffusion are accepted as mechanisms explaining this effect. In this work carrier concentration depth profiles were studied in various GaAs multi‐layered epitaxial structures grown on SI GaAs substrates before and after various heat treatment procedures in order to study the diffusion and outdiffusion processes. It is concluded that the role of the diffusion is negligible and the out‐diffusion process is insignificant, and the main, i.e. the determining effect in the compensation process is the growth mechanism of the layer. The impurities set free from the substrate by chemical etching processes rebuilt into the growing layer. In addition formation of EL2 centres may be initiated by As rich gas phase composition following the in‐situ etching.
Microhardness Anisotropy and Slip Systems in Biphenyl
Authors: Marwaha R. K. , Shah B. S. 
Published: January 2007

AbstractThe results of a study of the variation of hardness with load on the (001), (010), and (100) surfaces of biphenyl using the microindentation technique are presented. The microhardness anisotropy due to plastic deformation is explained in terms of the possible slip systems in biphenyl.
Quench Hardness Anisotropy of Rhombohedral Crystals: Calcite
Authors: Joshi D. R. , Pandya J. R. 
Published: January 2007

AbstractVariation of microhardness with orientation of indenter (A) and quenching temperature Tq is studied on freshly cleaved surfaces {100} of natural rhombohedral crystals of calcite by producing Knoop indentations for various applied loads. The relation between hardness HA and quenching temperatures for the high loads (40–80 g) is graphically established. It also depends on the crystal orientation. The anisotropic indices are also determined.
Plastic Deformation of Cesium Iodide Single Crystals at High Temperatures
Authors: Urusovskaya A. A. , Demchenko V. V. 
Published: January 2007

AbstractThe plastic deformation of CsI crystals of three crystallographic orientations 〈100〉. 〈110〉. and 〈111〉 at temperatures from 423 to 773 K (0.5 to 0.86Tm) and strain rates from 2 × 10−3 to 10−5 s−1 is studied. Four‐stage stres‐strain curves were found, three stages being more and more distinct with an increase in temperature up to 623 K above which stage III prevails. For all the temperatures, strain rates and oreintations studied the superplasticity features (jerky flow, deformation localization, active dynamical recovery etc.) were observed. The thermal activatoin analysis has shown that the rate of high temperature deformation of CsI is controlled by dislocation climb limited in its turn by mobility of cation vacancies (quasiviscous creep).
An Isoperibolic Reaction Twin Calorimeter for Investigating Precipitation
Authors: Velich V. , Söhnel O. , Costa‐Bauzá A. , Kroupa M. 
Published: January 2007

AbstractAn isoperibolic reaction twin calorimeter is described and its application to studying precipitation is shown. This technique is suitable for determining both the total reaction enthalpy and also, in specific ranges of supersaturation, kinetics of the process. The total enthalpy of BaSO4 and CaC2O4 · H2O precipitation at 25 °C was determined as −16.2 and −18.1 kJ mol−1, respectively. The spontneous precipitation of these compounds affected by mixing reactant solutions together proceeds through initial surge of nucleation and fast crystal growth that steeply diminishes. No major wave of secondary nucleation during precipitation was observed.
On Measuring Impurity Absorption Spectra of Semiconductors by Photoacoustic Spectroscopy
Authors: Neumann H. 
Published: January 2007

AbstractTheoretical relations are derived for the amplitude of the photoacoustic signal of a gas‐coupled cell for thick semiconductor samples including the influence of multiple reflections of light within the sample. It is shown that in the range of low absorption coefficients characteristic of impurity absorption spectra the sensitivity of the cell can be enhanced by using a highly reflecting metal as backing material. Numerical estimates for CuInSe2 are given to illustrate this effect.
On the Influence of Twinning Processes on Columnar Crystallite Growth in Electrodeposited Films
Authors: Shadrow V. G. , Tochitskii T. A. , Boltushkin A. V. 
Published: January 2007

AbstractAn investigation of columnar crystallite growth during the electrodeposition of fcc Ni and hcp Co‐W films has been made. It has been shown that the twinning processes not only promote the transformation of the initial orientation to the growth texture, but also lead to the change of the orientation of long columnar axes, the twinning processes in the fcc metal films exerting more significant influence on the columnar growth character than in the hcp ones.
Structure of a Manganese (II) Complex Containing Saccharin and 1,10‐Phenanthroline: [Mn(Sacch)2(o‐Phen)2(H2O)2] · H2O
Authors: Jianmin Li , Huidong Chen , Qiangjin Wu , Xintao Wu 
Published: January 2007

AbstractThe X‐ray crystal structure of the mononuclear manganese(II) complex containing saccharin and 1,10‐phenanthroline, [Mn(Sacch)2(o‐Phen)2(H2O)2] · H2O, is reported. The manganese atom has a geometrical structure of hexa‐coordinated distorted octahedron, saccharins interact with the central atom through water molecules.
The Epitaxial Orientation of Al on Si
Authors: Tempel A. , Büschel M. , Gantz T. 
Published: January 2007

AbstractIt is shown that the epitaxial growth of Al on Si {111} favours the epitaxial relation
{111} Si ‖ {100} Al; 〈110〉 Si ‖ 〈110〉 Al
instead of the more expected relation
{111} Si ‖ {111} Al; 〈110〉 Si ‖ 〈110〉 Al.
The elastic energy density of the epitaxial layer in the first case mounts to about 40% of that belonging to the second relation. The calculation of the elastic energy density in both cases is based on the assumption of pseudomorphical epitaxial film overgrowth between deposit and substrate supercells.
Polytypism in MX2 Compounds: A Case of Mixed Equilibrium Phases
Authors: Ahmad Shandar , Wahab M. A. 
Published: January 2007

AbstractClassical polytypism in MX2‐type compounds has been investigated. It has been established that polytypism can be understood, not as the case of independent stacking of A, B, or C layers but in terms of basic structural units, the most stable and only equilibrium phases of the given compounds. Other polytypes are formed only as a result of various equivalent positions that these units can take a given cell height. A criterion to predict whether a given compound would exhibit polytypism is also suggested. Several problems in applying ANNNI and other spin models to polytypism have been pointed out and a modified Hamiltonian is suggested.
Growth and Characterisation of Potassium Pentaborate Single Crystals
Authors: Raja C. Ramachandra , Gobinathan R. , Gnanam F. D. 
Published: January 2007

AbstractSingle crystals of potassium pentaborate were grown by the solution growth method. The grown crystals were characterised by optical transmission spectrum, differential thermal analysis, and thermogravimetric analysis. The coefficient of thermal expansion was also determined and the results discussed.
Optical Absorption Spectrum of Cu2+ Ions in Lithium Sodium Potassium Sulphate Single Crystal
Authors: Kumar R. Rama , Reddy B. C. Venkata 
Published: January 2007

AbstractSingle crystals of Copper‐doped Lithium sodium potassium sulphate were grown at room temperature. The optical absorption spectra were recorded at room and liquid‐nitrogen temperatures. The observed absorption bands have been attributed to an ion of Cu2+ in tetragonal symmetry with 2B1 as the ground state. A successful interpretation of all the observed bands have been made by taking into consideration spin‐orbit coupling associated with a tetragonal field.The crystal field parameters derived are Dq = 1045 cm−1, Ds = 1352 cm−1 and Dt = 457 cm−1.
The Effects of Polymeric Additives on the Crystallization of Compounds Found in the Evaporator Scales of Australian Sugar Mills (I), Compositions of the Scale Deposits
Authors: Doherty W. O. S. , Crees O. L. , Senogles E. 
Published: January 2007

AbstractThe composition of scales formed in multiple evaporator units at three Australian sugar mills have been determined using X‐ray fluorescence (XRF), high performance liquid chromatography (HPLC), X‐ray diffraction (XRD), thermogravimetry/differential thermal analysis (TG/DTA) and other analytical methods. The composition of the scales formed in each mill have been found to be significantly different and to depend on whether they originated from early or later stages of the evaporation process. Calcium oxalate (present as the di and monohydrate) was identified as a major component of the scales from one mill but was found to be only a minor component of the scales from the other two. The latter were shown to contain two or more forms of calcium phosphate as dominant phases. Amorphous or crystalline silica was found to be present in most of the scales examined.
Infrared Lattice Vibrations of CdGa2Te4
Authors: Neumann H. , Moise E. , Schwer H. , Krämer V. 
Published: January 2007

AbstractInfrared reflectivity spectra of CdGa2Te4 crystals are measured at room temperature in the wavenumber range from 180 to 600 cm−1 for the polarization directions E ⊥ c and E ‖ [111]. The frequencies of two E modes and two B modes are derived from the spectra. The frequencies of the modes with highest energy compare well with those of the corresponding modes in CuGaTe2 and AgGaTe2 which confirms the sphalerite‐like nature of these modes.
Analysis of the Load Dependence of Indentation Experiments
Authors: Berg B. , Grau P. 
Published: January 2007

AbstractIn most cases of microhardness Kick's law of similarity is unvalid. Therefore different equations were supposed to describe the real dependece of load and diagonal length of an indentation. These equations are independent from one another and it is not allowed to combine these. It is shown by means of experimental values from Joshi and Pandya that in a limited range of load different types of these equations can be used without a possibility to decide which gives a better description.
Ultrasonic Studies of Natural Oils and Fats of Plant Origin
Authors: Murthy V. R. , Kumar K. V. Siva , Reddy R. N. V. Ranga , Murthy Y. Narasimha 
Published: January 2007

AbstractInvestigations of specific volume and ultrasonic velocity as a function of temperature are carried out in different natural oils and fats of plant origin. From these studies it is found that the mango kernel fat exhibits liquid crystal‐like molecular order at T < 317 K. Various ultrasonic parameters like adiabatic compressibility, molar sound velocity, molar compressibility, van der Waal's constant, and intermolecular free length are evaluated. The variation of these parameters with temperature is also studied and the results are discussed critically.
Crystal Structure Analysis at Normal and Low Temperature Conditions
Authors: Luger Peter 
Published: January 2007

Abstract80 years after its discovery X‐ray diffraction presents itself as an outstanding method in structure determination which allows the most safe and accurate geometrical data of chemical structures to obtain compared to most other experimental methods. The major innovations in the recent past and the present state of crystal structure analysis are described together with some examples in inorganic and organic chemistry, including the use of synchrotron radiation.A variety of additional applications can be considered if the diffraction experiment is executed at low temperatures. Nitrogen gas stream devices and closed cycle helium cryostats are compared and their advantages/disadvantages are discussed. Finally some applications such as low temperature crystallization, temperature dependent structure analysis down to 20 K and deformation density work are illustrated.
Morphology of BBO Crystals and their Inclusions
Authors: Zhong W. Z. , Hong H. C. , Lu Z. P. , Zhao T. D. , Hua S. K. , Tang D. Y. , Zhao Q. L. , Zeng W. R. , Lin X. 
Published: January 2007

AbstractThis paper reports on the morphology and inclusions in the low temperature phase barium metaborate BaB2O4(BBO) crystal grown by an improved flux pulling method. The morphology of ideal BBO crystals and the relationship between the faces and the growth rate are given. The result that BBO has the symmetry L33P and belongs to the space group C3v−3m can therefore be concluded. It is found that the polarity of the BBO crystal along the Z (or c) axis has a visible influence on the morphology. The investigation of the inclusions in BBO crystals shows that these have a six‐fold symmetry which corresponds to the extension of flute‐like facets. It is also found that most of the inclusions have a regular geometric figure and can be regarded as the negative‐crystal structure which is due to the internal growth mechanism.
Microstructure and Texture Formation in Vacuum‐deposited Silver Films
Authors: Grantcharova E. , Dobrev D. 
Published: January 2007

AbstractThe role of the recystallization in the processes of microstructure and texture formation of silver films is compared for films: 1) deposited at high substrate temperatures (up to 720 K) and slowly cooled or quenched to room temperature; 2) deposited at room temperature and annealed at high temperatures. The grain growth distribution curves and the texture perfection are analysed. It is shown that the recrystallization processes taking place both during the slow cooling and during the annealing of the films lead to a formation of identical film structure with lower degree of texture perfection than in the case of quenched films.
Monte Carlo Simulation of Transient CSD in a Continuous Crystallizer under Stochastic Dispersion Effects
Authors: Dey Avijit , Gupta Bhaskar Sen 
Published: January 2007

AbstractMonte Carlo simulation is a very powerful tool for simulation of transient and steady state crystal size distribution (CSD) in a continuous crystallizer under stochastic dispersion effects. In the present work, transient CSD in a continuous crystallizer has been reported when shape factor and growth rate dispersions conform to normal distribution. For the steady state run, the algorithm reported by Sen Gupta and Dutta elsewhere has been used to validate the results obtained in the present work when the steady state is reached.
The Crystal and Molecular Structure of 1,18‐dibromooctadecane
Authors: Nakamura N. , Yamamoto T. , Kobayashi H. , Yoshimura Y. 
Published: January 2007

AbstractThe crystal and molecular structures of 1,18‐dibromooctadecane are determined precisely by X‐ray diffraction method. The results obtained are as follows: empirical formula, C18H36Br2, formula weight Mr = 412.27, crystal system, monoclinic, space group, P21/n, lattice parameters, a = 5.496(1), b = 5.403(1), c = 34.374(4) Å, β = 94.50(1)°, volume of unit cell, V = 1017.6(3) Å3, Z value, Z = 2, calculated density, Dx = 1.346 g/cm3, wave length of X‐ray, λ(CuKα) = 1.5418 Å, absorption coefficient, μ(CuKα) = 49.64 cm−1, F(000) = 428.00, temperature, T = 293 ± 1 K, R factor, R = 0.052, weighted R factor, Rw = 0.078 for 1019 unique observed reflection [I > 3σ (I)]. There are no unusual bond distances or angles. The structure obtained here is quite similar to that of 1,12‐dibromododecane.
Structural and Thermal Characterization of Zeolite Type X Modified by Successive Ion Exchange with Cobalt and Manganese Cations
Authors: Sarbak Zenon 
Published: January 2007

AbstractThe successive exchange of Co2+ and Mn2+ with NaX zeolite has been studied. Influence of the above cations on crystalline structure of zeolite type X and its thermal stability has been shown on the grounds of X‐ray diffraction, differential thermal analysis, and infrared spectroscopic measurements.
Ionic Conductivity of KBrKI Mixed Crystals
Authors: Kumar G. S. , Bhimasankaram T. , Prasad G. 
Published: January 2007

AbstractIonic conductivity studies have been made on the mixed KBrKI single crystals in the temperature region 150°–650 °C. The log σ versus 1/T plots indicate four different regions. The activation energies associated with different regions have been calculated and its variation with the composition of the mixed crystals is reported. The results obtained are correlated with the theoretical values calculated using Lidiard theory. An attempt is made to understand the results.
Semiconducting Properties of TI2Te3 Single Crystals
Authors: Hussein S. A. , Nassary M. M. , Gamal G. A. , Nagat A. T. 
Published: January 2007

AbstractElectrical conductivity and Hall effect measurements were performed on single crystals of TI2Te3 to have the general semiconducting behaviour of this compound. The measurements were done at the temperature range 160–350 K. All crystals were found to be of p‐type conductivity. The values of the Hall coefficient and the electrical conductivity at room temperature were 1.59 × 103 cm3/coul and 3.2 × 10−2 ω−1 cm−1, respectively. The hole concentration at the same temperature was driven as 39.31 × 1011 cm−3. The energy gap was found to be 0.7 eV where the depth of impurity centers was 0.45 eV. The temperature dependence of the mobility is discussed.
STGR Model and Relation between Growth Rate and Polytypism
Authors: Ahmad Shandar , Wahab M. A. 
Published: January 2007

AbstractEffect of crystal growth rate on polytypism has been explained using STGR model. It has been suggested that during the process of growth, polytypes are formed from a suitable combination of basic units in accordance with the rate of growth. At a slower rate the most probable polytype is predicted to be different from the one at faster rate.