bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low‐temperature LPE technique for the performance of visible AlGaAs (SC) lasers
Authors: Díaz P. , Prutskij T. A. , López F. 
Published: January 2007

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

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

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

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

AbstractThe X‐ray investigations of solid phases in the multicomponent systems KClKBrH2O, K2SO4(NH4)2SO4H2O and KNO3NH4NO3H2O were conducted and the crystal lattice parameters of mixed crystals forming in these systems were determined. It was confirmed that in the KClKBrH2O system the continuous solid solutions were formed and in the K2SO4(NH4)2SO4H2O system the solid solutions with a miscibility gap were formed. In the KNO3NH4NO3H2O system the presence of two series of mixed crystals, namely the mixed crystals between ammonium nitrate and the double salt KNO3 · 2 NH4NO3 and between potassium nitrate and the same double salt was confirmed. In this system a wide region of discontinuity (for xNH4NO3 = 0.083 – 0.67) also occurred.According to Roozeboom's classification, the KClKBrH2O system belongs to the 3rd type, the K2SO4(NH4)2SO4H2O to the 5th type (the discontinuous mixed crystals, the systems of peritonic type) and the KNO3NH4NO3H2O system is not comprised in this classification.
Influence of the Form Factor on Homogeneous Nucleation Kinetics
Authors: Kožíšek Z. 
Published: January 2007

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

AbstractThe structure and the depth distribution of radiation damage caused by erbium implantation (Ei = 100 keV, D = 5 × 1015 cm−2, Ti = LNT) in 〈111〉 cadmium telluride have been investigated by means of planar‐view and cross‐sectional TEM techniques. It is found that the implantation disturbes the CdTe target up to the depth well‐beyond the calculated projected range (that is ≳ × 5Rp). The resulting damage structure consists of well‐defined defects: precipitates, stacking faults, dislocation loops, and dislocation networks, which appear to be segregated with depth forming a sequence of homogeneously faulted zones. This characteristical and deep damage is suggested to be formed on dynamic annealing in response to internal stresses (caused by lattice parameter mismatch) which are high enough to produce plastic relaxation with dislocation generation and slip.This study is aimed at describing the ion‐implantation‐induced damage in single crystal cadmium telluride caused by Er+ ions by means of transmission electron microscopy.
Photoconductivity Spectra of n‐type CuInSe2 Single Crystals
Authors: Slifkin M. A. , Al‐Rahmani A. , Imanieh M. , Tomlinson R. D. , Neumann H. 
Published: January 2007

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

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

AbstractThin Al‐layers were prepared by Knudsen‐type evaporation of Al onto {111} Si in a custom built UHV‐reactor. Epitaxial growth was found on clean substrate surfaces with (7 × 7) reconstruction. In situ RHEED provides the epitaxial relationship
equation image
The epitaxial films show a twelve‐fold symmetry axis according to the combination of the 4‐fold and 3‐fold symmetry of the {001} deposit plane and of the substrate surface, respectively.
Influence of Profile Parameters on the IR Thickness Measurement of Thin Silicon Epitaxial Layers
Authors: Quick Ch. , Hild E. , Schley P. , Quick J. 
Published: January 2007

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

AbstractThe rhenium crystals were rolled in the {1000} 〈1120〉 orientation. Rolling produces cracks in crystals at low deformation (ϵ = 30%). It has been shown that microcracks in the volume of the crystal arise at a more earlier deformation stage than visible surface cracks.Recrystallization during subsequent annealing is strongly intensified with the start of crack formation. Stepwise facets of recrystallizated grains are often observed, this fact being connected with twinning lamellae recrystallization. Microcracks in the crystal body are completely eliminated during high temperature annealing. This process caused by diffusion over microcracks surfaces.
MOVPE of InP Using Trimethylindium – Trimethylamine Adduct
Authors: Keller B. P. , Oelgart G. , Pickenhain R. , Grummt G. , Seifert W. 
Published: January 2007

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

AbstractCalibration curves to determine the concentrations of shallow impurities in Si were usually established with the help of homogeneous doped samples at 4.2 K. The improvement of the lateral resolution power necessary to characterize inhomogeneous samples can be conveniently achieved by the use of superfluid helium. The calibration curves required for it were established at 2.0 K for P‐ and B‐doped Si and compared with the dependences measured at 4.2 K. Existing differences between these curves are discussed.