bluuebunny/crossref_metadata_2025 huggingface dataset:
Single Crystals of Cubic Ferrite Containing Only Fe3+ as Magnetic Ions
Authors: Rezlescu E. , Rezlescu N. , Craus M. L. , Pasnicu C. , Rezlescu L.
Published: January 2007

Single crystals of LiFe5O8 and Y3Fe5O12 are of considerable interest for microwave applications. These were grown by spontaneous crystallization from fluxed melts by slow cooling. The quality of the obtained crystals were analyzed by X‐ray diffraction and by measuring of the characteristic parameters (saturation magnetization σs, Curie temperature Tc, density D, hardness Hv). Although the both ferrites involve Fe3+ as the only magnetic ions which are responsible for the magnetic properties of these ferrites, several essential differences are found attributing to the particularity of their crystalline structure.

Les cristaux de LiFe5O8 Y3Fe5O12 suscitent un considerable interět pour les applications dans le domain de microondes. Le developpement des cristaux est provoqué par la cristalisation spontane, pendant le procesus de mélange des flux fondus, en regime de refroidissemnet lent. La qualité de ces cristaux ainsi obtenus a été analisée à l'aide de la diffraction des rayons X et du messurement des paramètres caractéristiques (magnetisation de saturation σs, température Curie Tc, dénsité D, dureté Hv). Quique les deux ferrites impliquent les Fe3+ comme les seuls ions résponsables pour les proprietés magnétiques, beaucoup d'autres differences sont trouvées provenant de la particularité de leur structure cristalline.
Surface Smoothing of Copper Single Crystals Using POM (Potential Oscillating Method)
Authors: Kipp S. , Lacmann R.
Published: January 2007

The deposition of metals is a process to get metallic coatings on metals. The potential oscillating method (POM) allows dissolution and deposition processes in parallel. Using this method the crystal's habit becomes more perfect, and the equilibrium form can be obtained. It is mostly dominated by the {111}‐ and the {100}‐face, as usual for cubic face centered crystals. The crystallographic faces develop more clearly and become smoother. This paper deals with the determination of the ideal conditions for the electrochemical experiment using copper single crystals, and the analysis of the surface topography using light microscopy, and scanning force microscopy.
Dependence of the Electric Properties and the Positron Lifetimes on the Dopant Content in La‐doped SrTiO3
Authors: Tang C. Q. , Xia Zhengcai , Yao Shude , Chen Shouyuan
Published: January 2007

The resistivity, the dielectric constant, and the positron lifetimes in La‐doped SrTiO3 have been measured for La content x of 0—10 at.%. It was found that with increasing x, the variations of the resistivity and the dielectric constant and the positron lifetime parameters are nonmonotonic. The positron experiments have shown that the La‐doping induces mainly formation of Sr vacancies and variation of Sr vacancy configuration; the most probable configuration is the isolated Sr vacancies (V) as x < 0.5 at.%, the associated defects (La V) for 0.5 < x < 1 at.%, and the associated defects (2 La V) above x = 1 at.%. The results suggest that the variation of the resistivity can be regarded as variation of electron density, and the variation of the dielectric constant results mainly from variations of the space‐charge polarizaion and Sr‐vacancy concentration and configuration.
Growth and Characterization of Urea‐(DL) Tartaric Acid Single Crystals
Authors: Lü M. K. , Meng F. Q. , Yang Z. H. , Yu W. T. , Zeng H.
Published: January 2007

A new organic UV nonlinear optical crystal urea‐(DL)tartaric acid [CO(NH2)2−(DL) C4H6O6] (abbreviated as U(DL)T) is reported. Large single crystals have been grown from aqueous solution by the cooling method. They belong to the monoclinic space group P21 and the lattice parameters are: a = 7.6973 Å, b = 23.3310 Å, c = 4.8727 Å, and β = 100.82°. The structure and some of its physical properties have been determined. The crystal is transparent from 0.24 to 1.95 μm. The efficiency of powder SHG is larger by one order of magnitude than that of KDP. Thus the crystal will be a useful NLO material.
Silicon Tubes for Microelectronic Applications Grown Directly from the Melt
Authors: Vanca V. , Dinu M. , Enache V. , Schlett Z.
Published: January 2007

A die‐free technique for growing large diameter silicon tubes (5–15cm) directly from the melt has been developed. The attained result was a constant tube wall thickness for a range of 7 to 0.2 mm at 1500 mm length limited by the equipment pulling stroke. It is shown that the inner pressure of the tube is function of the meniscus height at the growth interface. A speed is also presented. By means of experiments the thermal gradient at the solid‐liquid interfaces is determined.
The Crystal Rotation Rate in the Czochralski Growth with Up‐seed
Authors: Mokruchnikov Pavel W.
Published: January 2007

The crystal rotation rate per time in the Czochralski growth is represented. It was found that a change of the crystal rotation rate for solution systems is not necessary. But the change of the crystal rotation rate for melting systems can be linear.
Microstructures on Zirconium Trisulphide Single Crystals
Authors: Patel S. G. , Agarwal M. K. , Arora S. K.
Published: January 2007

Physical vapour transport grown single crystals of zirconium trisulphide have been examined by optical microscope, and the study of growth patterns on their finished surfaces reveal the screw dislocation mechanism by which the crystals have grown.
The Crystal and Molecular Structure of 4‐Hydroxy‐4′‐nitro‐ biphenyl and its Potassium Salt
Authors: Pfeil A. , Zugenmaier P.
Published: January 2007

The crystal and molecular structures of the title compounds have been solved by single crystal X‐ray analysis. 4‐Hydroxy‐4′‐nitro‐biphenyl (NBO) crystallizes in the centrosymmetric, monoclinic space group P21/n witha= 6.036(4) Å,b= 12.392(3) Å,c= 13.346(8) Å, β = 96.46(3)° and 4 molecules in the unit cell. Its potassium salt (NBOK) similarly belongs to P21/a witha= 11.277(2) Å,b= 7.3606(6) Å,c= 14.383(3) Å, β = 107.804(7)° and also 4 molecules in the unit cell. The structure of NBO was refined by full matrix least‐squares calculation toR= 0.043 for 1105 observed reflections, the structure of NBOK toR= 0.041 for 2288 observed reflections, respectively.

NBO and NBOK crystallize in layer‐like structures. The biphenyl molecules of NBO are arranged as corrugated ribbons in layers. The ionic and polar moiety of NBOK (potassium, oxygen, and crystal water) are separated by biphenyl units to form layers. The almost planar biphenyl units of NBOK are arranged in pairs and exhibit a short molecular distance of 3.08 Å within one pair.
Effect of Cu Ions on the Dipole Moments and Polarization of Strontium Barium Niobate Single Crystals
Authors: Xia H. R. , Wang C. J. , Yu H. , Chen H. C. , Song Y. Y.
Published: January 2007

The crystal growth, the ferroelectric hysteresis loops, and the infrared reflectivity spectra of coppermodified strontium barium niobate (SBN) single crystals are reported. Compared with the undoped SBN crystals, the copper‐modified crystals have stable hysteresis loops, the spontaneous polarization of which is about 0.30 C/m2, but that of the undoped SBN crystals is only about 0.12 C/m2. Their coercive field strength is all about 340 V/mm. The experimental results of the infrared spectra show that the infrared reflectivities vary as the orientations of the dipole moments owing to the copper‐doping. The c‐axis becomes the most stable orientation of the dipole moments, and the polarization will be locked and won't recede if the copper‐modified crystals are polarized into monodomains.
Oblique Phonons in Raman Scattering and IR Reflection of TeO2 Crystal
Authors: Syrbu N. N. , Cretu R. V. , Cebotari V. Z. , Mushinskii V. P.
Published: January 2007

The Raman scattering and IR reflectivity have been investigated for different crystal configurations. The contours of reflectivity spectra have been calculated. The angle dependence of polar vibrational modes in both reflectivity and Raman spectra have been investigated. The peculliarities of the transition from longitudinal mode to transverse one and vice versa both with and without changing of symmetry have been obtained. The phonon parameters and effective ionic charges of the anions and cations have been determined. It has been shown that there exists an effective ionic charge anisotropy of the oxygen and tellurium ions.
Mechanosynthesis and Mechanolysis of Solid Solutions of La2O3 with Some Rare Earth Oxides
Authors: Todorowsky D. , Terziev A. , Minkova N.
Published: January 2007

The effect of the mechanoactivation on Y2O3, Nd2O3 and CeO2, on mixtures of La2O3 with each of these oxides as well as on the solid solutions La2O3–CeO2 is studied. The activation causes a decrease of the individual oxides' unit cell parameters. The formation of solid solutions of La2O3 with the oxides studied is found. Under the conditions of activation in air no decomposition of La2O3–CeO2 solid solution is detected. The solution is, however, destroyed when the activation is carried out in the presence of acids.
Voronoi Polyhedra: A Useful Tool to Determine the Symmetry and Bravais Class of Crystal Lattices
Authors: Bohm J. , Heimann R. B. , Bohm M.
Published: January 2007

A handy PC‐supported method will be described to deduce the Bravais lattice (Bravais class) of a crystal lattice from an arbitrary set of lattice parameters. The method involves the construction of the related Voronoi polyhedron (Dirichlet domain, Wirkugsbereich, Fedorov parallelohedron, Wigner‐Seitz cell) whose metric relations between its edge lengths can be used to unequivocally identify the Bravais lattice. This is particularly useful if an unconventional setting of the unit cell, or inaccurately determined lattice parameters may result in misleading conclusions as to identify the correct Bravais lattice.
Anchoring Energy of Some Nematic Liquid Crystals at Aligment Layers of Different Topography
Authors: Frunza S. , Roques Y. , Farenc J. , Stoenescu D. N. , Traverse J. P.
Published: January 2007

Using a high electric field method, the anchoring energy was measured for tilted homogeneous cells filled with nematic liquid crystals (5CB, ZLI 1132). These cells contain aligment layers of five different types obtained either by SiO depositions at various incidence angles or by special polyvinylic alcohol (PVA) coatings. The observed differences in the anchoring energy values are due to the differences in the layer topography.
MOVPE growth of spontaneously ordered (GaIn) and (AlIn)P layers lattice matched to GaAs substrates
Authors: Gottschalch V. , Franzheld R. , Pietzonka I. , Schwabe R. , Benndorf G. , Wagner G.
Published: January 2007

A systematic study of the metal‐organic vapour‐phase epitaxial growth of (GaIn)P and (AlIn)P layers deposited on GaAs substrates with (001) and (110) orientation is presented. Special attention has been paid to the growth on (001)‐oriented wafers with different misorientations to the growth direction. The influence of the growth conditions on the properties of the epitaxial layers such as lattice mismatch, alloy composition, photoluminescence (PL) wavelength, FWHMs of PL peaks and atomic ordering is discussed. Layers with mirrorlike surfaces and various degrees of order could be deposited at growth temperatures Tg ranging from 595 °C to 750 °C for (GaIn)P and 720 °C to 800 °C for (AlIn)P. In addition to the influence of Tg on the Ga incorporation during the (GaIn)P growth we found the Ga distribution coefficient kGa to be affected by the misorientation of the substrates. kGa correlates presumably with the number of kinks and steps on the substrate surface.

Transmission electron diffraction (TED) and PL investigations show that the degree of order — often described by the ordering paramter η — depends strongly on Tg the ordering is more pronounced when the layers are deposited on substrates misoriented towards the (111) lattice plane. Strong ordering has been observed for (GaIn)P samples grown at 680 °C on substrates 2° misoriented towards the [110] direction and at 650 °C on substrates 6° misoriented towards the same direction. For the (AlIn)P samples striking ordering has been found when they were grown at 720 °C.
Graphical Representation of Various Models for Crystal Size Distribution in Continuous Flow Crystallizers
Authors: Nývlt Jaroslav , Hostomský Jiří
Published: January 2007

Plots of crystal size distribution of the following crystallizer models are compared: an ideal continuous‐flow MSMPR (mixed suspension, mixed product removal) crystallizer with a zero as well as non‐zero initial crystal size, an MSMPR crystallizer with size dependent growth of crystals, an MSMPR crystallizer with missing fines, an MSMPR crystallizer with agglomerative growth, and a series of MSMPR crystallizers simulating a crystallizer with nonideal agitation. The shape of the individual size distribution curves can serve as a diagnostic criterion in determination of the most probable model of crystallization.
Study of Imperfect Iron Doped NiAl Crystals with Laue Method
Authors: Zhang Hui , Zahn Gernot , Paufler Peter
Published: January 2007

By using an imaging plate, point defects and lattice distortion prior to and after plastic deformation has been studied with back reflection Laue method. This includes structure refinement with the intensity data extracted from back reflections only. Preliminary results show promising prospect. The intrinsic difficulties of Laue method have been addressed. Improvement possibilities will also be discussed.
Formation and Structure of TiZn‐Oxides
Authors: Steinike U. , Wallis Bettina
Published: January 2007

In powder mixtures of ZnO and TiO2 the compounds Zn2TiO4, ZnTiO3 and Zn2Ti3O8 can be formed as a result of solid state reactions. The mechanism of the double oxide formation is essentially determined by the microstructure of the powder mixture. Furthermore, the kind of the double oxide depends on the TiO2‐modification. There exist structural similarities between Zn2TiO4 (spinel) and TiO2 (anatase) on the one hand and ZnTiO3 and TiO2 (rutile) on the other hand. The compound Zn2Ti3O8 is formed only on the basis of the Zn2TiO4‐phase. The crystal structure of Zn2Ti3O8 was derived as a defect spinel. The unoccupied sites of cations are not arranged statistically, but they are ordered in the structure. This order leads to the decrease of the space group symmetry from Fd‐3m to P4332.
Vapour‐liquid‐solid Growth and Characterisation of N‐methylurea Crystals
Authors: Zha M. , Zanotti L. , Zuccalli G. , Ardoino M. , Capelletti R. , Paorici C.
Published: January 2007

A new growth method, based on a vapour‐liquid‐solid (VLS) mechanism, is reported for preparing single crystals of N‐methylurea (NMU), a material which appears to be a good alternative to urea for non‐linear optical applications in the “near UV‐visible” region of the spectrum. Details of the growth procedure are given and it is shown that large single crystals, with volumes up to 7 ÷ 10 cm3, can be obtained with satisfactory reproducibility and very fast growth rate. Structural and optical characterisation, still preliminary, are reported, which evidence a crystalline quality comparable to that of urea and N‐methylurea as previously grown with other growth techniques. Cryst. Res. Technol., Vol. 32, No. 1.
Characterisation of Bi2Se3 Crystals Highly Doped with Pb
Authors: Karamazov S. , Horák J. , Navrátil J. , Lošták P.
Published: January 2007

Pb‐doped Bi2Se3 crystals were prepared from starting elements Bi, Se and Pb of 5N purity in the concentration interval cpb = 0 – 4 × 1025 Pb atoms m−3 by a modified Bridgman method. The measured values of the transmittance and reflectance were used to determine the dependence of the absorption coefficient K on the photon energy for crystals with various values of cpb and to prove the shift of the short‐wavelength absorption edge with cpb. On the basis of the assumption of the validity of the “single valley” model, which can describe the lowest conductivity band of Bi2Se3, and using the values of the freecarrier effective mass in the directions perpendicular and parallel to the trigonal axis c we determined the value of the reduced Fermi energy η 300 K for crystals with various values of cpb. Using the value of η, we calculated the dependence of the Seebeck coefficient on cpb and compared it with the experimentally determined values. The comparison has shown that the increasing content of Pb atoms in the Bi2Se3 lattice leads to a suppression of the role of the mechanism of scattering by ionised impurities; at higher concentrations of Pb in the crystal the mechanism of scattering of free carriers by acoustic phonons becomes dominant. Further, the ideas on the nature of the point defects in the Bi2Se3(Pb) crystals are presented and the “anomalous” dependence of the free‐electron concentration on cpb is qualitatively accounted for.
Growth of the New Infrared Nonlinear Optical Crystal DCNP
Authors: Fang L. , Fang C. S. , Zhuo H. S. , Sherwood J. N.
Published: January 2007

This paper reports on the growth of 3‐(1,1‐dicyanothenyl)‐1‐phenyl‐4,5‐dihydro‐1 H‐pyrazole (DCNP) crystals in dimethylformamide. The effect of different solvents on the growth of DCNP has been investigated. Dimethylformamide was found to be a good solvent, Transparent DCNP single crystals were grown from this solvent. They are a promising infrared nonlinear material.
Vibrational Studies of Bis(thiourea) Cadmium Chloride and Tris(thiourea) Zinc Sulphate Semiorganic Non‐linear Optical Crystals
Authors: Selvasekarapandian S. , Vivekanandan K. , Kolandaivel P. , Gundurao T. K.
Published: January 2007

Single crystals of Bis(thiourea) cadmium chloride (BTCC), and Tris(thiourea) zinc sulphate (TZnS) have been grown from saturated aqueous solution by slow evaporation method at room temperature. The laser Raman and FT‐IR spectra on these crystals are recorded in the frequency range 50–4000 cm−1. The spectral data of BTCC and TZnS are interpreted on the basis of thiourea crystal vibrational data. The vibrational frequencies in the FT‐IR and Raman spectra of BTCC and TZnS establish that ZnSO4 and CdCl2 metal complex are coordinated with thiourea by the metal to sulfur bonds. The effect of the metal complexation on thiourea molecule and nature of bands due to different vibrational modes have been discussed. The lattice vibrational frequencies changes have also been observed and analyzed.
Growth, Characterization and Non‐Critical Phase‐Matching of Niobium‐Doped KTP Crystals
Authors: Jiyang Wang , Yaogang Liu , Jingqian Wei , Minghua Jiang , Zongshu Shao , Wenjun Liu , Shusheng Jiang
Published: January 2007

A series of niobium doped KTP (Nb: KTP) crystals has been grown. XRD and DTA experiments show that the Nb: KTP crystal structures do not differ from that of KTP (within experimental error) and that the melting points of the crystals increase with increasing Nb content. Synchrotron radiation topography revealed that the main defects of the crystals were growth sector boundaries, growth striations, inclusions and dislocations. Second harmonic generation experiments were performed using a 12.2% Nb:KTP and the d15 and d24 values of csystal were determined to be (3.7 ± 0.4) and (8.3 ± 0.8) × 10−9 esu, respectively. The relationship between phase‐matching angle and Nb content for a 1.064 μm laser was determined and in the case of a 4.0% Nb:KTP crystal, non‐critical phase matching was realized.
X‐ray Lang Topography and Infrared Spectroscopy in Quartz Crystals Grown Hydrothermally with Intermittent Runs
Authors: Guha A. K. , Annamalai N. , Kar T. , Sengupta S. P.
Published: January 2007

Growth defects in Y‐plates obtained from Y‐bar synthetic quartz crystals, grown hydrothermally with intermittent runs, have been studied for the first time by X‐ray Lang topography and infrared spectroscopy. To study the effect of interfaces on dislocation structures, the growth runs have been discontinued several (6 to 7) times by switching off the autoclaves from 30 min to 1 h. The dislocations were observed to change their directions at the generated interfaces, sometimes they stop at the in terfaces or move straight through the interfaces depending on the angles of the interfaces which are presumably low‐angle grain boundaries. The percentage transmission of infrared beam has also been measured as a function of the distance traversed in the crystal. The inverse anelastic loss (Q) decreases at the interface which is due to the greater accumulation of chemical impurities and H bonded OH− ions at these interfaces. The effect of in‐situ electric field on the topographic contrast has also been studied which reveal some interesting results on account of space charge polarization.
Ti‐adsorption on Se‐prereacted GaAs (110) surfaces studied by SXPS
Authors: Eckardt I. , Schröter T. , Tiedtke K. , Wagner N.
Published: January 2007

This study is embedded in the broader context of reactive metal overlayers and passivation on GaAs. High resolution synchrotron‐radiation photoemission experiments for Ti coverages on Se‐reacted GaAs (110) surfaces show that, contrary to clean Ti‐reacted GaAs (110) interface, there is no initial disruption (submonolayer reaction) of the surface involving both Ga and As atoms during early stage of interface formation. However, a delayed Ti involved reaction appears at a trigger coverage of about 1 ML involving only As atoms from the prereacted AsSe interface configuration continued by Stranski‐Krastanov growth mode. A second reacted phase starts to form two GaTi involved configurations replacing GaSe bonds near a Ti coverage of 4 ML. The preferential chemical trapping of Ti by Se atoms is associated with a smaller interface thickness very likely <10 ML instead of 50 ML in the case of clean Ti/GaAs (110) interface caused by mobile As atoms.
Effect of Neutron Irradiation and Annealing on the Intensity of the Copper Related 1.01 eV Emission Band in n‐type GaAs
Authors: Glinchuk K. D. , Prokhorovich A. V.
Published: January 2007

Effect of neutron irradiation (E = 2 MeV, ϕ ≤ 1015 n/cm2) and subsequent annealing (T ≤ 700 °C, t = 30 min) on the intensity of the copper‐related peaked at hvm =1.01 eV emission band in n‐type GaAs (n0 = 2 × 1018 cm−3) is studied. A strong irradiation‐induced increase of the above emission intensity was observed testifying about the irradiation‐stimulated growth in the concentration of copper‐related 1.01 eV radiative centres (CuGaVAs pairs). A model is presented to explain this effect.
Crystal Data, Electrical Resisitivity and Mobility in Cu3In5Se9 and Cu3In5Te9 Single Crystals
Authors: Parlak M. , Erçeleb Ç. , Günal İ. , Özkan H. , Gasanly N. M. , Çulfaz A.
Published: January 2007

X‐ray powder diffraction data were obtained for Cu3In5Se9 and Cu3Te9, which were found to crystallize in orthorhombic and tetragonal systems, respectively. The electrical resistivities and Hall mobilities of these compounds were investigated in the temperature range 35–475 K. Cu3In5Se9, was identified to be n‐type with a room temperature resistivity of 3 × 103 Ω·cm which decreases with increasing temperature. For T < 65 K impurity activation energy of 0.03 eV and for T > 350 K onset of intrinsic conduction yielding a band gap energy of 0.99eV were detected. The neutral impurity scattering was found to dominate at low temperatures, while in the high temperature region thermally activated mobility was observed. Cu3In5Te9 exhibits p‐type conduction with a room temperature resistivity of 8.5 × 10−3 Ω·cm decreasing sharply above 400 K and yielding an impurity ionization energy of 0.13 eV. The temperature dependence of mobility indicates the presence of lattice and ionized impuritiy scattering mechanisms above and below 160 K, respectively.
Field induced Increase of Pitch in Planar Cholesteric Liquid Crystals
Authors: Chilaya G. , Hauck G. , Koswig H. D. , Petriashvili G. , Sikharulidze D.
Published: January 2007

In cholesteric liquid crystals the application of an electric field parallel to the helix axis can change the wavelength of selective reflection. For decreasing pitch of the studied mixtures, the colour shift becomes more stable against the field‐induced transformation of the initial Grandjean structure into a confocal texture. In compounds with a low crossover frequency, a field induced increase of the pitch was observed at the switching between low and high frequency fields. The investigations allow new conclusions on the origin of the colour shift.
Characterization of a Flux‐grown NdxY1‐xAl3(BO3)4 Crystal by X‐ray Projection Topography
Authors: Hu X. B. , Jiang S. S. , Wang J. Y. , Huang X. R. , Liu W. J. , Zeng W. , Pan H. F.
Published: January 2007

NdxY1‐xAl3(BO3)4 (NYAB) single crystal was grown by the flux method using K2CO3MoO3 as a solvent. By x‐ray projection topography, the defects on a (0001) slice of the NYAB crystal are investigated. It is found that the main grown‐in defects in NYAB crystal are growth bands, growth sector boundaries and inclusions. The formation of defects is discussed and methods to reduce the defects are proposed.
Texture and structure of nickel‐molybdenum catalysts supported on alumina modified with sulfate and phosphate ions
Authors: Lewandowski Marek , Sarbak Zenon
Published: January 2007

A series of nickel‐molibdenum catalysts supported on alumina modified with sulfate and phosphate ions was studied. The studies involved texture evaluation measurements through N2 adsorption isotherms. Besides, IR spectroscopic and derivatographic studies were carried out. Results of the studies enable us to conclude that modification of the alumina support with the above ions leads to a significant decrease in its surface area and pore volume. Modification does not result in a change of the type of pores of the support, but in the change of their size dimention. The pores present on the surface of the catalyst have the shape of “ink‐bottles”. Modification with phosphate ions improves the thermal stability of the catalyst, whereas sulfate ions present on the surface of the catalyst undergo decomposition upon heating of the sample. Phosphate ions inhibit formation of aluminum molybdate, and instead form polymeric layer structures of phosphate on the surface of catalysts. Sulfate ions occur in the form of surface aluminum sulfate.
Influence of Rapid Thermal Processing on the Orientation Properties of PbTiO3 Thin Film
Authors: Zhu Jianguo , Xiao Dingquan , Peng Wenbing , Lan Fahua , Wan Deren
Published: January 2007

Rapid thermal processing (RTP) has developed in fabrication of ferroelectric (FE) thin films because it can reduce processing temperature and time. It also improves the properties of FE thin films compatible with semiconductor devices. The thin film samples used were prepared by a multi‐ion‐beam reactive cosputtering system (MIBRECS) at room temperature. The samples were then subjected to a post‐deposition annealing in a RTP system. It was found that PbTiO3 (PT) thin film can grow on amorphous or polycrystalline interfacial layer and the PT thin films annealed by RTP showed the prefered [110] and [100] textures.
The Crystal and Molecular Structure of 2‐(2′‐Cyano‐2′‐amido‐ethylenyl)‐pyridine
Authors: Öztürk S. , Akkurt M. , İde S. , Kepez M.
Published: January 2007

The title compound (C9H7N3O) has been determined from three dimensional X‐ray diffraction data. The crystals are monoclinic, a = 4.858(3) Å, b = 15.008(7) Å, c = 11.787(2) Å, ß = 94.107(2)°, V= 857.2(4) Å3, z = 4, Dcalc = 1.342 g. cm−3, space group P21/c. The structure was solved by direct methods and refined by full‐matrix least‐squares method (γ MoKα′, R = 0.0766).
The Crystal and Molecular Structure of the Complex Diaquatetrakis(imidazole)copper(II) Terephthalate Crystal Structure Containing Cu(II) Him and TA
Authors: Huaqiang Zeng , Min Yang , Xiaoying Huang , Xueyuan Chen
Published: January 2007

The title compound has been synthesized and its crystals structure determined at room temperature. MW = 536.01, monoclinic, space group C2/c, Z = 4, a = 22.193(5) Å, b = 8.038(2) Å, c = 15.699(4) Å, β = 119.64(2)°. The crystal structure consists of repeated [Cu(Him)4(H2O)2] (Him = imidazole) cations and non‐coordinated terephthalato dianions. The copper(II) ion displays an elongated octahedral coordination being linked to the four nitrogen atoms of the four imidazole ligands and to the two oxygen atoms of the two water molecules. The terephthalato dianions are hydrogen bonded to the four water molecules and four imidazole groups.
Growth of some urinary crystals and studies on inhibitors and promoters. II. X‐ray studies and inhibitory or promotery role of some substances
Authors: Natarajan S. , Rmachandran E. , Suja D. Blisin
Published: January 2007

Best conditions were established for the gel growth of three urinary crystals viz., calcium oxalate monohydrate, calcium hydrogen phosphate dihydrate and ammonium magnesium phosphate hexahydrate. The crystals grown were characterized using single crystal X‐ray diffraction techniques and density measurements. Crystal growth experiments were carried out by incorporating the extracts or juices of some natural products in the gel media. By carefully observing the changes in the growth of crystals (compared to control experiments carried out at the same conditions), results about the inhibitory or promotery role of the substance incorporated were obtained. It was found that the extracts or juices of many of the naturally occurring substances have interesting inhibitory or promotery effects. These results may have useful applications in the treatment of recurrent stone patients.
RbxK1‐xTiOPO4 Thin Films Grown on KTiOPO4 Substrates by Liquid Phase Epitaxy
Authors: Shi L. P. , Pun E. Y. B. , Chung P. S.
Published: January 2007

The properties of RbxK1‐xTiOPO4 thin films grown on KTiOPO4 substrates are reported. High quality films were obtained using the flux liquid phase epitaxy method, and optical waveguiding was observed in these epitaxial films. X‐ray analysis shows that the epitaxial films are single crystals films. Their cell constants are different from those of the substrates. The epitaxy growth rate and other film properties were compared for films grown on different faces. Two different surface morphologies were observed for films grown on (100) faces. The morphologies on (201) and (201) faces were also different. The quality of films grown on the (201) face was better. The reason for a structure inversion for films grown on the z− face is discussed.
Diffusion Control during Vapour Crystal Growth
Authors: Nanev Chr. N.
Published: January 2007

The crystal growth rate under diffusion control is considered. Together with nutrient diffusion, the physi‐sorption of an inert gas, which impedes the surface kinetics during vapour growth, is taken into consideration. In this way the size of the diffusion field surrounding vapour grown crystals was estimated. The relations obtained are checked with data for the growth of zinc single crystals in argon atmosphere. The appearance of shallow cavities on their basal faces is used as a morphological mark for growth under diffusion control. Besides, the microstructure of the inner edge of the macroscopically flat periphery, surrounding the shallow cavities is investigated experimentally, by means of SEM.
On the Kinetics of Solid‐Liquid‐Solid. Phase Transformation
Authors: Nývlt Jaroslav
Published: January 2007

Solid‐solid phase transformation of different hydrates or polymorphs in suspension proceeds in such a way that the metastable phase dissolves and the stable phase precipitates from the solution. If the starting point lies within the metastable zone of the stable phase, the transformation starts only after elapse of the corresponding induction period. In the case when the starting point is situated outside the metastable zone of the stable solute, the transformation proceeds without any delay. These theoretical considerations are illustrated by an example with recrystallization of calcium sulphate in presence of phosphoric acid; a small concentration change of the acid changes the kinetics significantly.
Viscosity Measurement of La3Ga5SiO14 Melt
Authors: Böttcher Klaus , Shimamura Kiyoshi , Fukuda Tsuguo
Published: January 2007

The viscosity of La3Ga5SiO14 melt was measured by a fixed‐crucible rotor technique in the range between 1520 and 1596 °C. The melt was found to be Newtonian. The viscosity data ranged between 73 and 97 mPa. s, decreasing with increasing temperature. The activation energy of the viscous flow and the volume of a viscous flow unit estimated from the measured data were 90 kJ/mol and 3 × 10−3 nm3, respectively.
Scale Formation on Cooling Surfaces in Crystallizers
Authors: Nývlt Jaroslav , Veverka František
Published: January 2007

Using a simple apparatus the effect of various parameters on encrustations formation was studied. Critical temperature difference and critical time of scaling were introduced as variables characterizing the tendency of the system to form encrustations. These parameters are linked with the metastable zone width of the system.
Generation of VGaTeAsVAs Complexes in Tellurium‐doped n‐type GaAs by Low‐temperature Annealing
Authors: Glinchuk K. D. , Prokhorovich A. V.
Published: January 2007

It is shown that low‐temperature annealing (T= 425 to 625 °C, t ⩾ 0.5 h) of tellurium‐doped n‐type GaAs crystals (n0 = 2 × 1018 cm−3) leads to a generation of VGaTeAsVAs complexes as a result of a diffusion of arsenic vacancies to VGaTeAs complexes or arsenic and gallium vacancies to isolated tellurium atoms. The observed regularities of generation of VGaTeAsVAs complexes as the annealing temperature and the annealing time are varied are well explained by the proposed model of diffusion‐limited formation of VGaTeAsVAs complexes.
Layer Systems on the Base of Nitrogen‐Doped Tantalum and Niobium with Enhanced Stability
Authors: Fedorenko A. I. , Starikov V. V. , Pozdeev Yu L. , Lykov I. N.
Published: January 2007

There are presented the results of the investigation of tantalum‐ and niobium‐based metal‐oxide bilayers degration in dependence on chemical composition of base metal. Nitrogen dissolved in metal increases stability of chemical composition and electrical properties of oxide films grown on the metal surface by anodic oxidation. This improves reliability and life time of electronic devices containing tantalum‐ or niobium‐based layer systems. The best positive effect of doping tantalum and niobium by nitrogen was achieved after preliminary refining of these metals from oxygen. When nitrogen concentration in the base metal essentialy exceeds its solubility limit at room temperature and nitride phases are formed the dielectrical properties of oxide film get worsen.
Synthesis and Luminescence Characteristics of LiMgAlF6:Ln3+ (Ln = Ce, Eu, Tb)
Authors: Tao Feng , Zhou Xiao‐Jing , Zhu Shi‐Fu , Zhao Bei‐Jun , Hong Guang‐Yan , You Hong‐Peng
Published: January 2007

By solid state reaction, LiMgAlF6 and LiMgAlF6: Ln3+ are synthetized with the ratio 120/100/110 of LiF/MgF2/AlF3, at 1008 K, in high‐purity Ar stream. Their crystal structure which belongs to hexagonal system are determined by X‐Ray‐Diffraction (XRD). Luminescence characteristics of Ce3+, Eu3+, Tb3+ and sensitization of Ce3+ to Tb3+ in LiMgAlF6 are studied. It is shown that the sensitization of Ce3+ to Tb3+ is efficient and a bright green emission is observed.
IR and X‐Ray Powder Diffraction Studies on Ba2Me(HCOO)6. 4 H2O (Me = Co, Ni, Zn)
Authors: Stoilova D. , Koleva V.
Published: January 2007

It has been established that the double salts Ba2Me(HCOO)6. 4 H2O (Me = Co, Ni, Zn) are isostructural with Ba2Cu(HCOO)6. 4 H2O (trinclinic space group P1 = C1i). The infrared spectra of the double salts and their deuterated analogues have been recorded and the internal modes of the formate groups and the water molecules are reported. The analysis of the infrared spectra indicates that some of the internal formate modes (v3 and v4) reflect the existence of three crystallographically independent formate ions. The comparatively large frequency separations between the asymmetric and symmetric C–O stretching modes is a criterion for the different C–O bond lengths within each formate groups. The number and the positions of the bands in the high frequency range (4000–2300 cm−1) are evidence for the existence of two inequivalent water molecules. The apearance of four uncoupled O–D modes in the spectra of the isotopically dilute samples shows that the water molecules are asymmetric. The librational modes of the water molecules are discussed as well.
The Investigation of Relation Between the Transition Temperature and the Unit Cell Volume in (K1‐xCsx)2ZnCl4 Mixed Crystals
Authors: Ahn H. Y. , Jeong H. T. , Jeong S. Y.
Published: January 2007

The relation between the phase transition temperature and unit cell volume in the (K1‐xCsx)2ZnCl4 mixed crystals was studied. The phase transition temperature of A2BX4 family is dependent on the size of cation and anion (FABRY and PEREZ‐MATO). That is, the transition temperature of crystal decreases with increasing unit cell volume. In this study we investigated this property of mixed crystals with the increasing mixture ratio. From the current study, we obtained the result that in the mixed crystals (K1‐xCsx)2ZnCl4, the increase of x induces the increase of unit cell volume, so that TI decreases with increasing unit cell volume. In order to determine the distribution of the substituted Cs+, using the near IR and UV spectrophotometer, we investigated both the band gap energy and the type of transition.
Impurity Striations During Bridgman Growth of InSb
Authors: Potard C. , Dusserre P. , Duffar T.
Published: January 2007

InSb single crystals have been grown by the gradient freeze method. Striations close to the seeding interface have been evidenced by X‐ray topography and correlated to temperature and growth rate oscillations. It is shown that these striations are related to light impurity segregations and that a non‐linear process should be taken into account to explain the phenomena.
Theoretical Study of Recrystallization Process of Amorphous Ge Layer Subjected to Pulsed Excimer (XeCl) Laser Radiation
Authors: Klinger D. , Auleytner J. , Z̊ymierska D.
Published: January 2007

Transient temperature profiles have been studied theoretically in amorphous germanium thin films on the crystal substrate during heating by a single laser pulse. Computer calculations have been based on the Fourier equation of the heat flow. The calculated threshold value of the energy density for the melting the whole of amorphous layer have been reported for excimer laser radiation.
In situ Observed Twin Formation on ZnSe Crystals Growing by Sublimation
Authors: Schönherr E. , Freiberg M. , Hartmann H.
Published: January 2007

ZnSe crystals were grown by sublimation in closed ampoules between 1335 K and 1365 K. The growth was observed in situ with a video camera after an abrupt change of the supersaturation. The crystals developed preferably {110} faces. Repeatedly a nucleus was formed in ortho‐twin position on a small {111} face which truncated the corner of three adjacent {110} faces. The repeated twin formation led to a preferred growth into the relevant 〈111〉 direction. The twinning already occurred at a low supercooling of less than 1 K and accelerated the growth distinctly.
A Study of Convection, Striations and Interface Shape in InP Crystals Grown by the Double‐Crucible LEC Technique
Authors: Fornari R. , Gilioli E. , Mignoni G. , Masi M.
Published: January 2007

A doublecrucible (DC) Czochralski setup has been used for the pulling of semi‐insulating Fe‐doped InP. The level of the Fe‐doped melt in the growth crucible is replanished with the undoped InP from the reservoir crucible. In this way, since the distribution coefficient of iron is very small (about 0.001), the Fe concentration in the growth crucible is virtually unchanged during the pulling so that the axial Fe concentration is much more uniform than in standard LEC crystals. The use of two concentric crucibles has great implications in terms of convective flows, stability of the melt temperature and interface shape. In this paper we report the results of a study on striations and structural defects in InP grown from a double‐crucible LEC arrangement. A dimensionless relationship for correlating striation features with melt motions is also proposed.
Selected 3d‐Transition Metals in Gallium Antimonide: Vanadium, Titanium and Iron
Authors: Lauer S. , Danilewsky A. N. , Meinhardt J. , Hofmann R. , Dörnen A. , Benz K. W.
Published: January 2007

3d‐transition metals are known to produce deep levels in III‐V semiconductors like gallium arsenide or indium phosphide. In this work, gallium antimonide was doped with the most promising candidates vanadium, titanium and iron according to the predictions of the energetic positions of the 3+/2+‐charge transfer levels in the bandgap. For optimum incorporation of dopants several growth methods (travelling heater method THM, Czochralski CZ and liquid phase electroepitaxy LPEE) were used. The grown crystals were characterized by photoluminescence and electrical measurements. No deep levels in the forbidden band were found in the case of vanadium and titanium. Vanadium shows a scavenging effect on unintentional impurities. Titanium tends to form inclusions. In gallium antimonide doped with iron an acceptor was found with an activation energy of 26 meV. The findings support the predictions of Tersoff concerning charge transfer levels.
Kinetics of Indium Phosphide Epitaxial Growth Using Metal Organic Precursors
Authors: Masi M. , Cavallotti C. , Radaelli G. , Carrà S.
Published: January 2007

The deposition kinetics of InP using metal‐organic precursors is presented. The proposed chemical mechanism involves both gas phase and surface reactions. The fundamental hypothesis adopted in deriving the mechanism was a dual site dissociative adsorption of the precursors on the growing surface. In any case, all the rate constants either were taken from the literature or estimated through thermochemical methods. In addition, the deposition reactor was simulated by means of a monodimensional model that accounts for the main reactor features through the boundary layer theory.
Direct radiative effect modeled for regional aerosols in central Europe including the effect of relative humidity
Authors: Iorga G. , Hitzenberger R. , Kasper‐Giebl A. , Puxbaum Hans
Published: January 2007

In view of both the climatic relevance of aerosols and the fact that aerosol burdens in central Europe are heavily impacted by anthropogenic sources, this study is focused on estimating the regional‐scale direct radiative effect of aerosols in Austria. The aerosol data (over 80 samples in total) were collected during measurement campaigns at five sampling sites: the urban areas of Vienna, Linz, and Graz and on Mt. Rax (1644 m, regional background aerosol) and Mt. Sonnblick (3106 m, background aerosol). Aerosol mass size distributions were obtained with eight‐stage (size range: 0.06–16 μm diameter) and six‐stage (size range 0.1–10 μm) low‐pressure cascade impactors. The size‐segregated samples were analyzed for total carbon (TC), black carbon (BC), and inorganic ions. The aerosol at these five locations is compared in terms of size distributions, optical properties, and direct forcing. Mie calculations are performed for the dry aerosol at 60 wavelengths in the range 0.3–40 μm. Using mass growth factors determined earlier, the optical properties are also estimated for higher relative humidities (60%, 70%, 80%, and 90%). A box model was used to estimate direct radiative forcing (DRF). The presence of absorbing species (BC) was found to reduce the cooling effect of the aerosols. The water‐soluble substances dominate radiative forcing at the urban sites, while on Rax and Sonnblick BC plays the most important role. This result can be explained by the effect of the surface albedo, which is much lower in the urban regions (0.16) than at the ice and snow‐covered mountain sites. Shortwave (below 4 μm) and longwave surface albedo values for ice were 0.35 and 0.5, while for snow surface albedo, values of 0.8 (shortwave) and 0.5 (longwave) were used. In the case of dry aerosol, especially for urban sites, the unidentified material may contribute a large part to the forcing. Depending on the sampling site the estimated forcing gets more negative with increasing humidity. When humidity changes from 50% to 90%, the factor of forcing change for Graz is about 3 times larger than that for Linz (3.8) and about 5 times greater than that for Vienna (2.4). At the mountain stations the change in forcing with increasing humidity is much less pronounced because of the high surface albedo. The influence of the aerosol mixing state on the single‐scattering albedo as well as on DRF is investigated for all sampling sites. As expected, the single‐scattering albedo was found to have lower values for internal mixture than for external mixture.
Effects of tidal stresses on volcanic activity at Mount Etna, Italy
Authors: Sottili G. , Martino S. , Palladino D. M. , Paciello A. , Bozzano F.
Published: January 2007

Here we model quantitatively the stress and strain induced by tidal forces as possible triggers of Mount Etna eruptions during 1989, 2000 and 2001, by means of 2D numerical analysis by finite difference method applied to the volcano edifice. Spectral and vectorial analysis of tidal acceleration indicates that the quasi‐diurnal, semi‐diurnal and ter‐diurnal constituents may have induced decompressions up to some kPa in the shallow (i.e., 1,500 m) gas‐saturated magma reservoir, which controlled magma vesiculation and the timing of lava fountain activity from the South East Crater (SEC). We consider the geological heterogeneities in the volcanic edifice (i.e., rock geometries and properties, feeder conduit and vent systems, volcanic landforms), the magma properties (i.e., Bulk modulus, volatile content) and the ongoing volcano‐tectonic stresses (i.e., volcano flank deformations), which strongly influence the response of eruptive activity to tidal forces. Indeed, the tidal factor may act on flank deformation concomitant to shallow magma inflation. The implications of our model may help understand the eruptive behaviour and the disequilibrium state of the volcano and may be useful for hazard assessment at Mount Etna.
Cluster observations of an auroral potential and associated field‐aligned current reconfiguration during thinning of the plasma sheet boundary layer
Authors: Marklund G. , Johansson T. , Lileo S. , Karlsson T.
Published: January 2007

Cluster observations are used to illustrate the reconfiguration of an auroral potential structure encountered at the poleward boundary of the central plasma sheet within the Southern Hemisphere premidnight auroral oval. The reconfiguration from a symmetric U shape to an asymmetric S shape takes place between two consecutive crossings by Cluster spacecraft 1 and 2, moving along roughly the same orbits and separated in time by 16 min. During this time the plasma conditions poleward of the boundary changed dramatically. The fluxes of energetic electrons decreased, as did the intensities of the associated small‐scale field‐aligned currents (FACs) and the ambient plasma density. These changes were particularly pronounced in a narrow region adjacent to the boundary. The reconfiguration of the potential structure, and of the associated FAC system consistent with this, are consistent with the predictions by Marklund et al. (2004).