Showing papers on "Single crystal published in 1992"
TL;DR: In this paper, single-crystal epitaxial thin films of the isotropic metallic oxides Sr1−xCaxRuO3 (0 ≤ x ≤ 1) were grown on miscut SrTiO3(100) substrates in situ by 90° off-axis sputtering.
Abstract: Single-crystal epitaxial thin films of the isotropic metallic oxides Sr1–xCaxRuO3 (0 ≤ x ≤ 1) were grown on miscut SrTiO3(100) substrates in situ by 90° off-axis sputtering. These thin films exhibit low isotropic resistivities, excellent chemical and thermal stability, good surface smoothness, and high crystalline quality. Furthermore, the lattice parameters and magnetic properties can be varied by simply changing the strontium/calcium ratio. These epitaxial thin films, and their multilayer structures with other oxide materials, can be used for the fabrication of superconducting, ferroelectric, magneto-optic, and electro-optic devices.
509 citations
TL;DR: In this paper, the Ni 2p and O 1s XPS of NiO single crystals were measured using monochromatic Al K alpha radiation and different treatments of the crystals allow the authors to give a description of the influence of defects on these spectra.
Abstract: The Ni 2p and O 1s XPS of NiO single crystals were measured using monochromatic Al K alpha radiation. Different treatments of the crystals allow the authors to give a description of the influence of defects on these spectra. The Ni 2p3/2 spectrum of in-situ-cleaved NiO exhibits clearly visible features at 854.1 ev 855.6 eV and 861 eV. The intensity ratio changes after ion bombardment and an additional peak at 852.2 eV appears. Apart from a slight increase in linewidth the O 1s spectrum remains unchanged. The O 1s spectrum from an in-situ-cleaved NiO single crystal exhibits only a single peak at 529.4 eV which can be fitted by a Gaussian line profile. Further measurements allow the authors to attribute the well known O 1s satellite at 531.2 eV to emission from oxygen-containing species adsorbed at defects.
242 citations
TL;DR: In this article, the magnetic flux distribution in high-Tc YBaCuO (YBa2Cu3O7) single crystals with in-plane anisotropy was studied.
Abstract: Indicator ferrimagnetic films with in-plane anisotropy are applied for studying the magnetic flux distribution in high-Tc YBaCuO (YBa2Cu3O7) single crystals. Induction gradients are measured to estimate the critical current density Jc. Temperature dependences of Jc are found to be different for different field directions. For the field along the orthorhombic c-axis Jc∥ab exhibits an exponential temperature decay. In the case of H∥ab, however, Jc∥ab is changed just a little up to 70 K and then drops sharply near Tc.
232 citations
TL;DR: In this paper, the sputtered ZnO layer has been found to be one of the best buffer layers because of the physical properties of ZnOs are nearly analogous with those of GaN.
Abstract: In hydride vapor phase epitaxial (HVPE) growth of GaN, the sputtered ZnO layer has been found to be one of the best buffer layers because of the fact that physical properties of ZnO are nearly analogous with those of GaN. With a ZnO buffer layer, the reproducibility of growing GaN single crystal by HVPE has been greatly improved. The GaN films grown by this method show excellent crystalline, electrical, and optical properties. In particular, the Hall mobility of 1920 cm2 V−1 s−1 at 120 K is the highest value that has ever been reported by HVPE.
228 citations
TL;DR: In this paper, a model is proposed as deduced from a six-dimensional (6D) Patterson analysis, where six different atomic hypersurfaces are located on node and body-centre sites of the 6D lattice.
Abstract: Perfect single grains of the AlPdMn icosahedral phase have been used for structure determination by X-ray and neutron diffraction. Owing to the large difference between X-ray and neutron scattering factors, information is gained on the atomic positions of the three elements. A model is proposed as deduced from a six-dimensional (6D) Patterson analysis. Six different atomic hypersurfaces are located on node and body-centre sites of the 6D lattice. The superstructure that leads to a face-centred lattice is mainly due to a strong chemical ordering, all the palladium being on the even node and odd body centre of the 6D cube. The resulting 3D structure contains icosahedral clusters similar to the external shell of the Mackay icosahedron, with two kinds of chemical decoration. The structure may also be described via a quasi-periodic stacking of fivefold planes. Each set of planes is characterized by an average chemical composition and local order. This kind of description helps in the understanding of quasi-crystal growth, formation of dislocations and dynamic properties.
228 citations
TL;DR: In this article, the first successful lattice-matched growth of InGaN was reported on sapphire substrates, where the x-ray diffraction line width was about 20% smaller than that of films grown on the same substrate.
Abstract: We have achieved InGaN growth on sapphire substrates at temperatures substantially higher than conventional growth temperatures for InGaN. When the growth temperature was changed from 500 (conventional) to 800° C (this work) in InGaN, the x-ray diffraction line width (full width at half maximum) decreased from 100 to 30 min. At 77 K, edge emission was observed in PL. In order to further improve crystalline quality, we have investigated ZnO as a lattice-matching substrate. First, the surface treatment and the resistance to the reducing atmosphere at high temperatures was briefly investigated. We report the first successful lattice-matched growth of InGaN. The x-ray diffraction line width of InGaN grown on ZnO was about 20% smaller than that of films grown on sapphire substrates, thus using lattice-matched substrates was shown to have an effect on improving the crystalline quality of InGaN. Single crystal InGaAlN has been also realized on sapphire substrates. The indium, gallium and aluminum contents were 2.2, 22.5 and 74.3%, respectively. The optical transmission characteristic of this InGaAlN was measured.
224 citations
TL;DR: The temperature and time dependences of the thermal conductivity below 260 K are shown to be described by a phenomenological model that involves thermally activated jumping motion between two nearly degenerate orientations, separated by an energy barrier of ∼260 meV.
Abstract: We report the first measurement of the thermal conductivity of single crystal ${\mathrm{C}}_{60}$. We observe that orientational disorder significantly reduces the thermal conductivity, evidenced by a large jump in the thermal conductivity at the 260 K orientational-order transition. The temperature and time dependences of the thermal conductivity below 260 K are shown to be described by a phenomenological model that involves thermally activated jumping motion between two nearly degenerate orientations, separated by an energy barrier of \ensuremath{\sim}260 meV.
196 citations
TL;DR: In this paper, a sliding test was performed on polycrystalline diamond coatings with a range of surface roughness, and the results indicated that the wear resistance of the coatings is comparable to that of natural, single-crystal diamond.
171 citations
TL;DR: In this article, the lattice parameters and crystal structures of the low temperature quartz-type (low-quartz) forms (space group P3 1 21) of SiO 2 and GeO 2 were refined from single crystal X-ray diffraction data under hydrostatic pressures up to 10.2GPa for SiO2 and 5.57 GPa for GeO2.
Abstract: Lattice parameters and crystal structures of the low temperature quartz-type (low-quartz) forms (space group P3 1 21) of SiO 2 and GeO 2 were refined from single crystal X-ray diffraction data under hydrostatic pressures up to 10.2GPa for SiO 2 and 5.57GPa for GeO 2 . R W (F) values range from 2 to 5%. GeO 2 -quartz is an almost perfect high-pressure model for SiO 2 -quartz:At 10GPa the geometry of the SiO 2 -quartz structure approaches that of GeO 2 at ambient pressure.
162 citations
TL;DR: In this article, single crystal solid solutions with compositions Bi 8 Sb 32 Te 60, Bi 9 Sb 31 Te 60 and Bi 10 Sb 30 Te 60 were grown using the Traveling Heater Method (T.H.M.).
157 citations
01 Oct 1992
TL;DR: In this article, a single crystal of pure C70 is grown from the vapour phase and the structure and morphology of these crystals are studied by means of X-ray diffraction and TEM measurements.
Abstract: Single crystal of pure C70 are grown from the vapour phase and the structure and morphology of these crystals is studied. By means of X-ray diffraction and TEM measurements five different phases are observed. The observed phases are (from high to low temperatures) fcc, rhombohedral, ideal hcp (c/a=1.63), deformed hcp (c/a=1.82) and a monoclinic phase. The occurrence of these different phases and the phase transitions is accounted for in a simple model. For the monoclinic structure a model for the stacking of the orientationally ordered molecules in the lattice is proposed. For both the hcp and fcc phases a Lennard-Jones type interaction potential is used to calculate bond strengths, lattice energies and the theoretical morphology.
TL;DR: In this article, the authors measured the evolution rates of quenched-in hydrogen from 80 to 800 K using a quadrupole mass spectrometer in an ultra high vacuum system.
Abstract: Hydrogen detrapping in high purity iron was studied by measuring evolution rates of quenched-in hydrogen from 80 to 800 K using a quadrupole mass spectrometer in an ultra high vacuum system. The peak of the evolution rate was observed at 395 K in single crystal specimens and 415 K in polycrystalline specimens with a heating rate of 1 K min−1. Effects of grain size and deformation on the evolution rate was also studied. It was shown that the results are consistent with the evolution rates calculated with the binding energy B = 0.51 ± 0.02 eV and the trap density term γCT = (4 ∼ 15) × 10−5 in polycrystalline iron, and B = 0.47 ± 0.02 eVand γCT = (2 ∼ 13) × 10−5 in single crystal iron. The dominant traps are considered to be grain boundaries in polycrystalline specimens and dislocations in single crystal specimens.
TL;DR: In this paper, the dependences of critical current on the temperature and magnetic field and the currentvoltage characteristics in response to incident microwave radiation are measured in the direction of the c-axis of the 80 K superconducting phase (Bi, Pb)2Sr2CaCu2Oy bulk single crystal.
Abstract: The dependences of critical current on the temperature and magnetic field and the current-voltage characteristics in response to incident microwave radiation are measured in the direction of the c-axis of the 80 K superconducting phase (Bi, Pb)2Sr2CaCu2Oy bulk single crystal. Josephson junctionlike behavior is successfully observed, and it shows that the single crystal itself is composed of Josephson junctions along the c-direction and that its electrical transport in this direction is limited by intrinsic tunnel barriers existing in the single crystal.
TL;DR: The 18 vibrational modes expected from group-theoretical analysis have been obtained in the polarized Raman spectra of ZnWO 4 single crystals and six internal modes of the WO 6 octahedra have been assigned.
Abstract: The 18 vibrational modes expected from group-theoretical analysis have been obtained in the polarized Raman spectra of ZnWO 4 single crystals. The six internal modes of the WO 6 octahedra have been assigned. The temperature dependence of the frequencies and linewidths of the internal modes is related to anharmonic terms in the crystal potential
TL;DR: In this paper, U3Si∼5 has been thoroughly investigated with respect to crystal chemistry and magnetic properties; for most compounds, magnetic studies have been carried out at low temperatures for the first time (2 to 300 K, 0 to 5 T).
TL;DR: In this paper, the authors used high-energy and low-energy electron diffraction and X-ray photoelectron spectroscopy measurements to show that the natural and synthetic diamond surfaces maintained their crystallinity even after the hydrogenation.
Abstract: Hydrogenation of diamond has been carried out using the electron-cyclotron-resonance microwave plasma chemical-vapor deposition apparatus. According to reflection high-energy and low-energy electron diffraction and X-ray photoelectron spectroscopy measurements, the natural- and synthetic-diamond surfaces maintained their crystallinity even after the hydrogenation. Seebeck effect measurement and the temperature dependence of the resistance revealed an appearance of deep acceptor levels in the hydrogenated diamond layer. The diffusion depth of the hydrogen by the plasma treatment (2 h, 830°C) was roughly estimated to be ~0.6 µm from the drain current-voltage characteristics of a rudimentary MISFET using the hydrogenated diamond.
TL;DR: The topographic and magnetic surface structure of a natural single crystal of magnetite (Fe304), a common mineral, has been studied from the submicrometer scale down to the atomic scale with a scanning tunneling microscope having nonmagnetic tungsten as well as ferromagnetic iron probe tips.
Abstract: The topographic and magnetic surface structure of a natural single crystal of magnetite (Fe304), a common mineral, has been studied from the submicrometer scale down to the atomic scale with a scanning tunneling microscope having nonmagnetic tungsten as well as ferromagnetic iron probe tips. Several different (001) crystal planes were imaged to atomic resolution with both kinds of tips. A selective imaging of the octahedrally coordinated Fe B-sites in the Fe-O planes, and even a selective imaging of the different magnetic ions Fe2+ and Fe3+, has been achieved, demonstrating for the first time that magnetic imaging can be realized at the atomic level.
TL;DR: In this paper, the effect of oxygen on resistivity of a C 60 single crystal and the temperature (160-570K) dependence of ϱ have been studied. And the authors found that resistivity increases by a factor of 10 4 on absorption of oxygen; the estimated concentration is 4% O 2 eer C 60.
TL;DR: In this article, the electrical conductivity of the layered compounds TlInS 2, TlGaS 2 and TlGeSe 2 was studied as a function of the temperature, perpendicularly and parallel to the layer planes.
TL;DR: In this paper, the critical current density of a single crystal of the high-temperature superconductor Bi2Sr2Ca1Cu2O8 was improved by irradiation with high energy Sn ions.
Abstract: Large enhancements in the critical current density Jc were produced in single crystals of the high‐temperature superconductor Bi2Sr2Ca1Cu2O8 by irradiation with high energy Sn ions. In addition, the irreversibility line was moved to considerably higher magnetic fields. In contrast with analogous studies on Y1Ba2Cu3O7, there was little, if any, selective pinning when the magnetizing field was applied parallel to the linear, ion‐damage‐produced tracks.
TL;DR: In this paper, the authors reported on the study of oriented carbyne layers prepared using three different techniques: 1) chemical carbonization of a poly(vinylidene fluoride) film, 2) ion sputtering of graphite, and 3) condensation of carbon vapor produced by an electrical arc.
TL;DR: Sizable single crystals of C6O have been synthesized and doped with potassium, and above the superconducting transition temperature Tc, the electrical resistivity p(T) displays a classic metal-like temperature dependence.
Abstract: Sizable single crystals of C6O have been synthesized and doped with potassium. Above the superconducting transition temperature Tc, the electrical resistivity p(T) displays a classic metal-like temperature dependence. The transition to the superconducting state at Tc = 19.8 K is extremely sharp, with a transition width ΔT
TL;DR: In this article, it was shown that the optical damage resistance of undoped LiNbO3 is increased with an increase in the Nb content of the crystal, and that the crystal quality, as represented by x-ray rocking curve peak width, has no correlation with the Optical damage resistance.
Abstract: Lithium niobate single crystals with various [Li]/[Nb] ratios were grown by the Czochralski method from melts having compositions varying between 45.5–58 mol % Li2O. Their optical damage resistance was characterized by measurement of the photoinduced birefringence change. Their crystal quality was characterized by x‐ray topography and x‐ray rocking curves. The photoinduced birefringence change increased with an increase in the Li content of the crystal. The Li‐poor crystals, which were richer in Nb content than the crystal with the congruent composition, showed the smallest birefringence change, in spite of the fact that the x‐ray rocking curve width of these Li‐poor crystals was much wider than the congruent crystal. It is concluded that the optical damage resistance of undoped LiNbO3 is increased with an increase in the Nb content of the crystal, and that the crystal quality, as represented by x‐ray rocking curve peak width, has no correlation with the optical damage resistance.
TL;DR: In this article, single crystals of YBa2Cu3O7−δ (001) and Sr2RuO4 (001), which have the K2NiF4 structure and display a metallic resistivity behavior in the a−bplane between 300 and 4.2 K, were grown by floating zone melting technique.
Abstract: Single crystals of Sr2RuO4 were grown by the floating zone melting technique. The crystals have the K2NiF4 structure and display a metallic resistivity behavior in the a‐b‐plane between 300 and 4.2 K (ρab≂10−4 Ω cm at 300 K). The in‐plane lattice mismatch between YBa2Cu3O7−δ (001) and Sr2RuO4 (001) is smaller than 1.3%, better than that to SrTiO3 {100}. Epitaxial films of YBa2Cu3O7−δ with Tc(R=0) as high as 86 K have been grown on Sr2RuO4 crystals. The epitaxial growth of YBa2Cu3O7−δ on Sr2RuO4 was revealed by four‐circle x‐ray diffraction as well as by transmission electron microscopy.
TL;DR: In this article, a photo-voltage of up to 600 mV was obtained by electron injection from the conduction band of ultrathin polycrystalline films of FeS[sub 2] (pyrite) on anatase by chemical vapor deposition.
Abstract: Ultrathin (10 to 20 nm thick), polycrystalline films of FeS[sub 2] (pyrite) were grown on TiO[sub 2] (anatase) by chemical vapor deposition. The FeS[sub 2] films were characterized using optical absorption and high-resolution electron microscopy. Photoelectrochemical solar cells, using TiO[sub 2] (anatase) coated with FeS[sub 2] ultrathin films, generated high open-circuit photo-voltages, of up to 600 mV, compared with a single crystal of pyrite electrode (200 mV). The photoelectrochemical behavior shows a strong dependence of photovoltage and photocurrent on the pH of the solution. This paper reports that it is explained by electron injection from the conduction band of FeS[sub 2] to the conduction band of TiO[sub 2]. Regeneration of holes is taking place by electron transfer from the redox system in the electrolyte.
Patent•
01 Oct 1992TL;DR: For example, the nickel-base superalloy as mentioned in this paper can be used to improve the grain boundary strength by adding small amounts of boron and carbon, and optionally hafnium.
Abstract: There is provided by the present invention nickel-base superalloys for producing single crystal articles having improved tolerance to low angle grain boundaries and an improved balance between cyclic oxidation and hot corrosion resistance. The improved tolerance arises from the discovery that nickel-base superalloys suitable for casting as single crystal articles can be improved by the addition of small, but controlled, amounts of boron and carbon, and optionally hafnium, and is manifested principally by improved grain boundary strength. As one result of this increased grain boundary strength, grain boundary mismatches far greater than the 6° limit for prior art single crystal superalloys can be tolerated in single crystal articles made from the nickel-base superalloys of this invention. This translates, for example, into lower inspection costs and higher casting yields as grain boundaries over a broader range can be accepted by visual inspection techniques without resort to expensive X-ray techniques. These alloys are especially useful when directionally solidified as hot-section components of aircraft gas turbine engines, particularly rotating blades and stationary vanes. The superalloy contains by weight percent, 7-12 Cr, 5-15 Co, 0.5-5 Mo, 3-12 W, 2-6 Ta, 2-5 Ti, 3-5 Al, 0- 2 Cb, 0.1-0.2 Hf, 0.05-0.07 C, 0.002-0.05 B, and nickel.
TL;DR: The authors have successfully grown single crystals of La 2-x-y Nd y Dr x CuO 4 by the traveling-solvent floating-zone method and enable us to investigate the anisotropic transport properties of the LTT phase.
Abstract: We have successfully grown single crystals of La 2-x-y Nd y Dr x CuO 4 (x=0,0.12,0.20;y∼0.4) by the traveling-solvent floating-zone method. All of these crystals show a tlattice instability to the low-temperature tetragonal (LTT) phase and enable us to investigate the anisotropic transport properties of the LTT phase. For x=0.12, various transport coefficient show a discontinuous jump at the phase transition (evidence for a first-order transition), and superconductivity is suppressed almost completely, while the effects are much reduced for x=0.20, which show a bulk superconductivity with reduced T c
TL;DR: The crystal structures of two ternary, chalcopyrite-structured semiconductors, CuInSe2 and CuInTe2, have been determined from single crystal X-ray diffraction data as mentioned in this paper.
Patent•
18 Mar 1992TL;DR: In this article, a method of producing a Czochralski-grown silicon single crystal stably and efficiently with high production yield, which comprises the steps of setting pulling conditions such that at least a portion of a growing single crystal (28) having a temperature in excess of 1150°C is spaced upwardly from a surface of silicon melt (14) by a distance greater than 280 mm.
Abstract: A method of producing a Czochralski-grown silicon single crystal stably and efficiently with high production yield, which comprises the steps of setting pulling conditions such that at least a portion of a growing silicon single crystal (28) having a temperature in excess of 1150°C is spaced upwardly from a surface of silicon melt (14) by a distance greater than 280 mm; and pulling the growing silicon single crystal (28) upward while maintaining the pulling conditions. The silicon single crystal produced by this method has an excellent oxide film dielectric breakdown strength. An apparatus (2) for carrying out the method is also disclosed.
TL;DR: In situ scanning tunnelling microscopy (STM) was used to study the electrodeposition of copper onto Au(111) and Au(100) electrodes from sulphuric and perchloric acid electrolytes.