Showing papers on "Single crystal published in 1977"
TL;DR: In this article, the structure parameters of AlN and GaN using X-ray intensities from single crystals collected with an automatic single crystal diffractometer were refined using a single crystal detector.
555 citations
416 citations
TL;DR: In this paper, three single crystal and two polycrystalline Pt surfaces were studied, one single crystal was cut to expose the smooth, hexagonally close-packed plane of the fee Pt crystal (the (111) surface).
283 citations
TL;DR: In this paper, the silver density in the high-temperature α-form consists of a tetrahedrally coordinated equilibrium position ( 1 4 0 1 2 ) and a three-coordinated saddle point (0.39 0.39 ).
205 citations
TL;DR: The mode of growth and the structure of the layers were studied by Auger electron spectroscopy and low-energy electron diffraction as mentioned in this paper, which showed certain similarities but also some striking differences between Ag/W and Au/W as well as a strong crystallographic anisotropy of adsorption and condensation.
Abstract: Silver and gold were evaporated up to several monolayers in thickness onto W single-crystal surfaces of the 110 and 100 plane types in the temperature range between 300 and 1300 K. The mode of growth and the structure of the layers were studied by Auger electron spectroscopy and low-energy electron diffraction. The results are compared with thermal desorption spectroscopy data and work-function change measurements. They show certain similarities but also some striking differences between the two systems Ag/W and Au/W as well as a strong crystallographic anisotropy of adsorption and condensation.
174 citations
TL;DR: In this paper, the single crystal elastic constants and their first pressure derivatives have been measured by means of the ultrasonic pulse superposition technique for the NaCl-structure oxides CaO, SrO, and BaO.
169 citations
TL;DR: In this article, the crystal habit common to Be, Cr, Mn and Fe was found to be rhombic dodecahedra truncated by {100} degrees of truncation.
Abstract: Fine metal crystallites with diameters 200~2000 A made by evaporating a metal in an atmosphere of an inactive gas were studied by electron microscopy. It is found that the crystal habit common to Be, Cr, Mn and Fe, which are bcc just below the melting point, is rhombic dodecahedra truncated by {100}. Fcc metals show six different types of crystal habit. However,only one, viz. octahedra truncated by {100}, is a single crystal and all the others have twins. Various degrees of truncation were found both for rhombic dodecahedra and octahedra. Crystallites with certain degrees of truncation are possibly Wulff polyhedra.
165 citations
TL;DR: The surface structures of the growing organic crystals do not corresond to planes in their reported bulk crystal structures and are evidence for epitaxial growth of pseudomorphic crystal forms.
Abstract: The surfaces of the normal paraffins (C3–C8) and cyclohexane have been studied using low‐energy electron diffraction (LEED). The samples were prepared by vapor deposition on the (111) face of a platinum single crystal in ultrahigh vacuum, and were studied both as thick films and as adsorbed monolayers. These molecules form ordered monolayers on the clean metal surface in the temperature range 100–220 K and at a vapor flux corresponding to 10−7 Torr. In the adsorbed monolayers of the normal paraffins (C4–C8), the molecules lie with their chain axes parallel to the Pt surface and Pt[110]. The paraffin monolayer structures undergo order–disorder transitions as a function of temperature. Multilayers condensed upon the ordered monolayers maintained the same orientation and packing as found in the monolayers. The surface structures of the growing organic crystals do not corresond to planes in their reported bulk crystal structures and are evidence for epitaxial growth of pseudomorphic crystal forms. Multilayer...
155 citations
TL;DR: In this paper, single crystals of CdSnO3, Cd2SnO4, ln2TeO6 and CdIn2O4 were grown by either flux or high pressure methods.
147 citations
TL;DR: In this paper, the authors measured the Ramaman intensities of single crystal H2O, D2O and HOD ice Ih from −4 to −150°C.
Abstract: Raman intensities of single crystal H2O, D2O and HOD ice Ih were measured from −4 to −150°C. The cc, aa, ca, aa′ (c is the unique axis) polarizability components were measured from 20 to 4000 cm−1. Shoulders are observed on the high frequency side of the νOH and νOD bands of HOD which we attribute to combination bands between νOH and νOD and lattice modes. Intensities in the OH stretching region are interpreted using bond polarizability theory. The ratio of anistropy to mean polarizability for the OH bond was found to be 1.81. The analysis of the intensities suggests that those hydrogen bonds that statistically parallel to the c axis are slightly more linear than those that are equatorial to the c axis. The effects of intermolecular coupling of OH stretching vibrations are very evident in the spectra. However, it appears that such coupling is not the principal cause of the breadth of the isotropic part of the symmetric OH stretch band at −4°C. Evidence is presented that indicates extensive coupling of lib...
142 citations
TL;DR: In this paper, single crystal semiconductors were coated with n-type TiO~ by a chemical vapor deposition technique, and the electron and hole transfer properties across the heterojunction so produced were investigated.
Abstract: Single crystal semiconductors (n-Si, p-Si, n-GaAs, p-GaAs, n-GaP, n-In.P, and n-CdS) were coated with n-type TiO~ by a chemical vapor deposition technique, and the electron and hole transfer properties across the heterojunction so produced were investigated. The quality of the deposited TiO~ film depended upon several factors including temperature and substrate material. When high quality crack-free TiO2 coats were obtained on n-type substrates, the substrate was stabilized with no dissolution during the photo-oxidation of water. However, the oxidation was due o~y to the photoexcitation of the TiO~, and any holes produced in the substrate were not transferred through the TiO~ to the solution. The use of p-type substrates coated with TiO2 as photocathodes was limited by band-bending requirements at the p-n heterojunction and the TiO~-solution interface.
TL;DR: In this paper, the magnetic properties of hexagonal Fe 2 P single crystal are studied by the measurements of magnetization, susceptibility, thermal expansion and electrical resistivity along the principal crystallographic axes.
Abstract: The magnetic properties of hexagonal Fe 2 P single crystal are studied by the measurements of magnetization, susceptibility, thermal expansion and electrical resistivity along the principal crystallographic axes. It is found that the saturation magnetization per molecule and the Curie temperature are 2.94 µ B and 208.6 K, respectively, and the anisotropy constant K 1 is 2.32×10 7 erg/cm 3 at 4.2 K, which is considerably larger than the values in 3d-transition compounds. The thermal expansion and the electrical resistivity show discontinuous changes at the Curie temperature indicating that the ferromagnetic to paramagnetic transition of Fe 2 P is accompanied by the first-order transition due to magnetoelastic effects. The exchange striction obtained from the measurement of thermal expansion is discussed on the basis of the theory of Bean and Rodbell.
TL;DR: In this paper, a complex plane representation was used to analyze frequency dependent a c conductivity data from samples of single crystal and polycrystalline β-Alumina, and measurements were made from room temperature to around 300°C in vacuum.
Abstract: The now well established technique of complex plane representation is used to analyze frequency dependent a c conductivity data from samples of single crystal and polycrystalline β-Alumina. Measurements were made from room temperature to around 300°C in vacuum. Wayne Kerr Bridges B. 221 and B. 601 with external source (Krohn-Hite 4200 Oscillator) and detector (Marconi TF1100 Valve Voltmeter) gave a frequency range of 500 HZ to 2 MHZ. Electrical contact was made via nickel or platinum foils in pressure contact with evaporated metal electrodes. Prior to measurement every specimen was annealed to 300°C in vacuum, within the conductivity rig, to eliminate moisture from the system.
TL;DR: Work hardening was found nearly independent of grain size for sizes below 1 μm, consistent with an absence of cell formation in sub-micron grain sizes as discussed by the authors. But the slip lengths for small grain sizes were found to be almost independent of strain.
TL;DR: In this paper, pressure sintered electrodes of cadmium selenide subsequently doped with Cadmium vapor have shown solar energy conversion efficiencies approaching /sup 3/sub 4/ of those of single crystal specimens in sunlight experiments.
Abstract: Pressure sintered electrodes of cadmium selenide subsequently doped with cadmium vapor have shown solar energy conversion efficiencies approaching /sup 3///sub 4/ of those of single crystal specimens in sunlight experiments. The cell CdSe/1F Na/sub 2/S-1F S-1F NaOH/C has operated at 5.1% conversion efficiency under AM2 conditions with polycrystalline electrodes. The relatively small sacrifice of efficiency from single crystal values of 7.5 +- 0.5% suggests the possibility of substantial cost advantage. The temperature and pressure conditions, cadmium doping procedure, material characterization, and the voltammetric behavior of the cell are discussed.
TL;DR: In this article, single crystal magnetostriction and thermal expansion measurements are reported on Tb 27 Dy 73 Fe 2, where a spin reorientation at T = 283K causes the sudden onset of a very large magnetostrictive distortion which yields a huge anomalous contribution to the linear thermal expansion The temperature and magnitude of this contribution is field controlled.
Abstract: Single crystal magnetostriction and thermal expansion measurements are reported on Tb 27 Dy 73 Fe 2 A spin reorientation at T = 283K causes the sudden onset of a very large magnetostrictive distortion which yields a huge anomalous contribution to the linear thermal expansion The temperature and magnitude of this contribution is field controlled The expansion coefficient d(\Delta\ell/\ell)/dT can be varied from +5 to +115×10-6/°K Normal magnetostrictive behavior is observed above 283K Below this temperature a change in the easy axis from the highly magnetostrictive [111] axis to the weakly magnetostrictive [100] direction causes an anomalous field dependence Here large external fields are required to saturate the moment along [111]
TL;DR: A single crystal neutron diffraction study of 6 C2H4O⋅46 D2O at 80 °K has confirmed the higher symmetry space group Pm3n and provided more precise structural data relating to the hydrogen bonding in this clathrate hydrate.
Abstract: A single crystal neutron diffraction study of 6 C2H4O⋅46 D2O at 80 °K has confirmed the higher symmetry space group Pm3n and has provided more precise structural data relating to the hydrogen bonding in this clathrate hydrate. The four unique hydrogen‐bonding interactions which form the edges of the polyhedra of involve three bonds with D...O lengths of 1.726, 1.757, and 1.761 A and three longer bonds of 1.797, 1.802, and 1.818 A. The three longer bonds form the edges of hexagons, while the shorter ones occur only in the pentagons. There is a definite trend for the longer bonds to be associated with shorter covalent O–D distances and greater deviations from O–D...O linearity. The scattering density of the ethylene oxide guest molecule was best fitted by a model with 24‐fold disorder, more consistent with small barriers to reorientation than with free rotation. A residual scattering density was also observed within the dodecahedra, corresponding to approximately 0.4 mole per unit cell of occluded air.
TL;DR: It is suggested that olivine glass may be formed as a result of shock at pressures above about 50 to 55 x 109 pascals and that further TEM observations of naturally shocked olivines may demonstrate the presence of glass.
Abstract: Transmission electron microscope (TEM) observations of an experimentally shock-deformed single crystal of natural peridot, (Mg_(0.88)Fe_(0.12))_2SiO_4, recovered from peak pressures of about 56 x 10^9 pascals revealed the presence of amorphous zones located within crystalline regions with a high density of tangled dislocations. This is the first reported observation of olivine glass. The shocked sample exhibits a wide variation in the degree of shock deformation on a small scale, and the glass appears to be intimately associated with the highest density of dislocations. This study suggests that olivine glass may be formed as a result of shock at pressures above about 50 to 55 x 10^9 pascals and that further TEM observations of naturally shocked olivines may demonstrate the presence of glass.
TL;DR: In this article, the second order Raman spectra of pyrolytic graphite has been obtained for both E∥c and Efc and the A2u out of plane mode is identified for the first time and occurs at 868 cm−1.
TL;DR: X-ray diffraction experiments of a single crystal of magnetite at 84 K were carried out to investigate the crystal symmetry below the transition temperature as discussed by the authors, and a new lattice deformation which makes crystal symmetry lower than rhom-bolaedral was clarified.
Abstract: X-ray diffraction experiments of a single crystal of magnetite at 84 K were carried out to investigate the crystal symmetry below the transition temperature. A new lattice deformation which makes the crystal symmetry lower than rhom-bolaedral was clarified. The extra reflections which appear in the low temperature phase were observed for the first time with X-ray diffraction. The extinction of (4, 4, \(\pm\frac{1}{2}\)) reflections, which was found by Iizumi and Shirane by means of neutron diffraction, was also confirmed. All the experimental results can be explained reasonably by assuming that the low temperature phase of magnetite has monoclinic symmetry, and the space group is either C s 4 - C c or C 2 h 6 - C 2/ c .
TL;DR: The Raman spectra in potassium selenate single crystal were measured over the temperature range 77∼300 K and the relationship between the soft-mode and the phase transition was discussed in this paper.
Abstract: The Raman spectra in potassium selenate single crystal were measured over the temperature range 77∼300 K. The spectra contain components due to internal vibrations of selenate radicals in the frequency region 300∼900 cm -1 , and those due to external lattice vibrations in the region 0∼200 cm -1 . The soft-mode was observed whose frequency decreases as the transition point T 1 (129.5 K) is approached from below. On the basis of these results the relationship between the soft-mode and the phase transition is discussed.
TL;DR: In this paper, a simple valence bond model based on the electron requirement of the Mo 6 octahedron to form 12 covalent bonds is proposed to stabilize the structure and have a strong influence on the superconducting transition temperature.
TL;DR: In this article, a model of a tilting system of the MnCl 6 -octahedra layer is introduced in order to understand essential features of structures of different phases and their transition behavior.
TL;DR: In this article, a high resolution energy loss spectra of 4 eV electrons reflected in the specular direction from Ni(100) surface clean or covered by the ordered structures obtained in the different stages of the metal oxidation, are analysed with reference to LEED patterns.
TL;DR: In this paper, strong blue colouration has been induced in rf sputtered thin films of WO3 by electrochemical injection of H+, Li+, and Ag+ ions from various solid and liquid electrolytes.
TL;DR: In this paper, low energy ion scattering in combination with LEED allows surface structure analysis in the case of gases adsorbed on single crystal surfaces, and strong shadowing and anisotropic effects observed are used to estimate the position of the adsorbated species.
TL;DR: It is proved, by calculating electron density in each stage, that the change of the crystal of R-α-cyanoethyl (S- α-methylbenzylamine)-cobaloxime changes its unit cell dimensions by X-ray exposure without degradation of a single crystal form.
Abstract: DURING serial structure analysis of cobaloxime derivatives1, aimed at interpreting the catalytic capability of the asymmetric hydrogenation2–5, we have found that the crystal of R-α-cyanoethyl (S-α-methylbenzylamine)-cobaloxime changes its unit cell dimensions by X-ray exposure without degradation of a single crystal form. The rate of the change was so slow that it was possible to collect the intensity data for several intermediate stages. We have proved, by calculating electron density in each stage, that the change reflects the racemisation of the cyanoethyl group.