Showing papers on "Single crystal published in 1975"

Formation and Properties of Porous Silicon and Its Application

Abstract: Preparation, properties, and applications of porous silicon film were investigated. Silicon single crystal is converted into porous silicon film by anodization in concentrated hydrofluoric acid at currents below the critical current density. When an n‐type silicon was anodized, the silicon surface was illuminated to generate holes which were necessary for this anodic reaction. The growth rate of the film, from n‐type silicon, was larger than that from p‐type silicon in this experimental condition. The crystalline structure was the same as that of silicon single crystal. A new isolation technique for bipolar integrated circuits was proposed by making use of the properties of the film such that it can be formed several microns thick and oxidized easily to form an insulator. The main feature of the technique is that it provides a means to form thick insulating film inlaid through the n‐type epitaxial layer without prolonged heat‐treatment. A preliminary experiment was carried out to test the practical usage of the technique.

Phase Transition in SnTe with Low Carrier Concentration

Abstract: The phase transition in SnTe was investigated on a single crystal with low carrier concentration (0.88×10 20 cm -3 ) by the neutron diffraction method. A second-order phase transition takes place a...

Te and Ge — doping studies in Ga1−xAlxAs

Abstract: The temperature dependence in the range 77–400 K of the carrier concentration, resistivity and mobility of a series of n and p-type single crystal, liquid-phase epitaxial layers of Ga1−xAlxAs are presented. These layers were doped, n-type with tellurium, and p-type with germanium to yield carrier concentrations in the range 1017 – 1018cm−3 at 295 K. Donor and acceptor ionization energies, eD and eA, are derived from the data. The dependence of eD on alloy composition is interpreted in terms of the known band structure variation in the alloy system.

Conduction electron polarization of gadolinium metal

Abstract: The zero field moment of Gd has been measured at 4.2K for a single crystal prepared by solid state electrotransport. It is magnetically very soft: the moment is (7.630+or-0.010) mu B per atom in the b direction and is slightly smaller in the c direction. The conduction electron polarization is 15% higher than previously estimated. Due to its small value the conduction electron susceptibility could not be measured accurately.

Order–disorder phenomena in adsorbed layers described by a lattice gas model

Abstract: Order–disorder transitions in adsorbed phases on single crystal surfaces manifest themselves by variations of the low energy electron diffraction (LEED) patterns. The present paper contains a theoretical treatment of the statistical properties of the simplest structure within this framework, namely a layer which may be described by a square lattice gas model with repulsive interactions between nearest neighbors and giving rise to a c2×2‐LEED pattern on the (100) surface of a fcc or bcc crystal. At a coverage ϑ=1/2 the relative intensities of the half‐order LEED spots are, within the kinematic approximation, shown to be identical to the expectation value of the spin‐correlation function of the two‐dimensional Ising model, averaged over an area corresponding to the coherence width of the electron beam. For ϑ<1/2 no analytic solutions are available, but the problem may be treated by means of the Monte Carlo technique, the results of which for ϑ=1/2 agree quite well with those from the analytic solution. The ...

Elasticity of microcrystals

Abstract: Acoustic velocities for a very small crystal are presented. The longitudinal velocities in the .3 mm single crystal of quartz are accurate to about 1–2%. The technique involves only optical measurements and is based on analysis of Brillouin scattering. The minimal sample size for acoustic velocity measurements using this technique is estimated to be about 0.01–0.03 mm.

Crystal dynamics of nitrogen: The cubic α-phase

Abstract: The technique of inelastic neutron scattering has been used to determine translational and librational lattice modes in a single crystal of solid nitrogen in the cubic $\ensuremath{\alpha}$-phase at 15 K. The measurements were concentrated at the high-symmetry points $\ensuremath{\Gamma}$, $R$, and $M$, where the degeneracies ease the task of symmetry assignments to the observed modes. The assignment was made on the correlation of the observed structure-factor variation with force-model predictions. The calculations were based on a general potential function which includes Lennard-Jones or six-exponential-type interactions as well as electric quadrupole forces. Good agreement was found between both the observed frequencies and the observed intensities and their calculated counterparts. The temperature dependence of selected modes has been established and it is compared to a recent self-consistent phonon calculation.

Dislocation structures in deformed single-crystal Ni3(Al, Ti)

Abstract: A transmission electron microscopy investigation of deformed Ni3(Al, Ti) single crystals has shown that, over the temperature range − 107°C to 917°C, there exist five distinct regions, each having a characteristic dislocation structure. No primary cube slip was observed at temperatures below approximately 450°C, the temperature of the peak proof stress. This observation makes untenable any theory which attributes the anomalous, positive dependence of the proof stress to an interaction between primary cube and octahedral slip.

Weak exchange in the Heisenberg linear chain: Structure and EPR of [N(n‐Bu)4]2[Cu(mnt)2]

Abstract: We report magnetic and x‐ray diffraction studies on a single crystal of [N(n‐Bu)4]2[Cu(mnt)2], where mnt = maleonitriledithiolato (C4N2S2)−2. The planar paramagnetic (S=1/2) [Cu(mnt)2]−2 anions crystallize in stacks with crystallographically equivalent sites, and the stacks are isolated by the cations. The compound crystallizes in space group C1i‐P1 of the triclinic system, with unit cell dimensions a=11.149(5), b=13.201(8), c=9.403(6) A, α=105.44(5) °, β=114.92(5) °, and γ=72.09(9) °, with Z=1. Static susceptibility measurements show exchange to be weak. Single crystal EPR studies yield a rich variety of multilined spectra, in spite of the magnetically concentrated nature of [N(n−Bu)4]2[Cu(mnt)2]. Analysis of the EPR spectrum in terms of a one‐dimensional exchange, J0=0.0107 cm−1, at 4.2 °K between successive [Cu(mnt)2]−2 ions along the c axis yields a surprisingly detailed picture of one‐dimensional exchange in a hitherto unobserved, weak coupling regime. The temperature dependence of J0 and the angular dependence of the Cu hyperfine splitting K (ϑ) permit spectra with both J0

Liquid‐phase‐epitaxial growth of single‐crystal LiNbO3 thin film

Abstract: The phase equilibrium of the LiVO3‐LiNbO3 pseudobinary system has been investigated, and a LiNbO3 single‐crystal thin film has been grown epitaxially onto the substrate by dipping a c‐plate LiTaO3 substrate into a LiVO3 flux solution. An x‐ray rocking curve indicated that the film had a high single crystallinity with good epitaxy. The composition ratio Li/Nb of the film was estimated to be close to the stoichiometric value Li/Nb≈1.0.

Properties of Vapour Phase Grown Mercuric Iodide Single Crystal Detectors

Abstract: The growth of red mercuric iodide single crystals by a dynamic sublimation method is described. Their characterization has been performed by means of optical and electrical measurements. Nuclear radiation detectors have been prepared with this material and their properties are evaluated in terms of a particles, ?- and X-rays spectrometry, detection efficiency, electron-hole pair creation energy and polarization effects. Finally the potential use of mercuric iodide in nuclear detection is discussed.

Plastic deformation of aluminum under repeated loading

Abstract: The plastic deformation behavior of high purity (99.999 pct) polycrystalline and single crystal aluminum under repeated stressing was investigated by studying the creep behavior. The creep behavior under repeated stressing (cyclic creep) was compared with the static creep behavior at identical peak stresses. The influence of such experimental variables as the applied stress, the amplitude of cyclic stress, the test temperature and the static creep rate prior to stress cycling were systematically examined. The most important experimental observation in this study was that the cycling of the creep stress could either enhance or retard the creep deformation, depending upon the combination of the experimental variables. The experimental variable that had the most significant influence on the cyclic creep behavior was the applied stress; the enhancement of the creep rate was observed above a threshold stress, while the cyclic stress retarded the creep deformation at lower stresses. The threshold stress was found to depend sensitively on temperature. The implications of the threshold stress were examined by an analysis of the work-hardening behavior.

Determination of Oxygen Chemical Diffusion Coefficients in Single Crystal SrTiO3 by Capacitance Manometry

Abstract: The oxidation kinetics of a single crystal of were measured with a tensivolumetric system over the temperature range 700°–975° at 0.03 atm oxygen pressure. The oxidation was found to be oxygen diffusion limited with an activation energy of . Combining the kinetic data with relative defect concentration data yielded an activation energy for oxygen self‐diffusion of . The enthalpy of formation of doubly ionized oxygen vacancies was calculated to be .

Method for preparing large single crystal thin films

Abstract: A method of making a large single crystal thin film not dependent upon the size or temperature resistance of the substrate crystal by first depositing an amorphous film of the crystalline material to be produced followed by heating of the amorphous film in such a manner that nucleation of epitaxial grains is propagated through the amorphous film whereby a single crystal thin film is produced.

The application of heterojunction structures to optical devices

Abstract: Basic factors are reviewed that enter into the successful operation of single crystal heterojunction devices, with an emphasis on the role of defects. The devices discussed include laser diodes, solar cells and electron emitters using negative electron affinity surfaces.