Photoelectrical properties of In/n-CuIn5Se8 Schottky barriers

CuIn₅Se₈ homogeneous crystals of n-type conductivity have been grown. Donor centers activation energy has been estimated. In/n-CuIn₅Se₈ Schottky barriers have been created and the first spectral dependencies of quantum efficiency of photoconversion of these structures have been derived. The nature of interband optical transitions has been interpreted and the band gap values for direct and indirect transitions in CuIn₅Se₈ crystals have been determined on the results of analysis of the Schottky barriers photoactive edge absorption. A possibility of utilization of CuIn₅Se₈ crystals in wide-band photoconverters of the optical radiation has been established.     

Reactant induced restructuring and corrosion of germanium-palladium catalysts during hydrogenation reactions

An anomalous rate enhancement with increasing conversion has been observed during the liquid phase hydrogenation of nitrobenzene and crotonaldehyde over Ge/Pd/C catalysts at ambient temperature and atmospheric pressure. Inductive coupled plasma atomic emission spectroscopy and electrochemical measurement of the oxidation state of catalysts during reaction revealed that the bimetallic particles were partially oxidized by the reactants, which resulted in Ge-dissolution and increased exposure of Pd on the surface. It is proposed that the surface and bulk composition of Ge/Pd catalysts are a function of their oxidation state. This behaviour is due to the unusually high mobility of Ge in the Pd lattice and to the good solubility of GeO₂ in polar solvents. The influence of hydrogen transport on the corrosion process and the stability of other X/Pd type bimetallic catalysts during liquid phase hydrogenation are also discussed.     

Activated gas plasma surface treatment of polymers for adhesive bonding

Polyethylene, polypropylene, poly(vinyl fluoride) (Tedlar), polystyrene, nylon 6, poly(ethylene terephthalate) (Mylar), polycarbonate, cellulose acetate butyrate, and a poly(oxymethylene) copolymer were treated with activated helium and with activated oxygen. Mechanical strengths of adhesive-bonded specimens prepared from treated and from untreated coupons were compared. Polyethylene (PE) and polypropylene (PP) showed the greatest increases in bond strength. Oxygen and helium were both effective with polyethylene, but polypropylene showed no improvement when treated with activated helium. The results with excited helium parallel the effects of ionizing radiation on these two polymers, as does the appearance of unsaturation bands in the infrared (965 cm^?1 in PE, and 887 and 910 cm^?1 in PP). Active nitrogen produced excellent bond strength with polyethylene but not with polypropylene. Of the remaining polymers examined, Tedlar, polystyrene, and nylon 6 showed the greatest improvement in bondability after treatment, and Mylar showed moderate improvement. Polycarbonate, cellulose acetate butyrate, and the poly(oxymethylene) copolymer gave approximately two-fold increases in lap-shear bond strength. In several cases, significant differences in response to time of treatment and type of excited gas were found.     

Calibrated,Registered Images of an Extended Urban Area

We describe a dataset of several thousand calibrated, time-stamped, geo-referenced, high dynamic range color images, acquired under uncontrolled, variable illumination conditions in an outdoor region spanning several hundred meters. The image data is grouped into several regions which have little mutual inter-visibility. For each group, the calibration data is globally consistent on average to roughly five centimeters and 0 1°, or about four pixels of epipolar registration. All image, feature and calibration data is available for interactive inspection and downloading at http://city.lcs.mit.edu/data.Calibrated imagery is of fundamental interest in a variety of applications. We have made this data available in the belief that researchers in computer graphics, computer vision, photogrammetry and digital cartography will find it of value as a test set for their own image registration algorithms, as a calibrated image set for applications such as image-based rendering, metric 3D reconstruction, and appearance recovery, and as input for existing GIS applications.     

Anomalies in the thermal and electrical conductivity of CuIn5Se8 crystals

Anisotropy, asymmetry, and other anomalies of electrical and thermal properties are revealed in CuIn₅Se₈ crystals. It is shown that the nature of these anomalies is associated with the natural coexistence of order and disorder in these ordered-defect compounds.     

Formation and optical properties of CuInSe<Subscript>2<Emphasis Type="Italic">x</Emphasis></Subscript>Te<Subscript>2(1−<Emphasis Type="Italic">x</Emphasis>)</Subscript> nanoparticles in a silicate glass matrix

Glasses containing nanoparticles of semiconductor CuInSe_2xTe_2(1?x) compounds (0≤x≤1) were fabricated by high-temperature melting of the mixtures of the glass-forming components and the corresponding compounds. Particles of average size 15–30 nm, whose characteristics were similar for compounds with different x, were formed. Optical absorption of the glasses near the fundamental absorption edge in the near-infrared and visible regions of the spectrum was studied, as well as the effect of additional heat treatment of glasses on their optical properties. The nature of the observed changes in the spectra with varying compound composition (the [Se]/[Te] ratio) was related to the possible transformations of the crystalline structure of nanoparticles.     

Structural and optical properties of AgIn<Subscript>5</Subscript>S<Subscript>8</Subscript> films grown by pulsed laser deposition

Thin AgIn₅S₈ films are grown on glass substrates by pulsed laser deposition using bulk crystals as targets, and their structure, chemical composition, surface morphology, and optical properties (transmission and reflection spectra in the range 0.5–2.5 µm) are investigated. The transmission and reflection data are used to evaluate the absorption coefficient of the films and the energies of direct and indirect interband transitions. The results obtained for laser-deposited AgIn₅S₈ films agree well with those for bulk crystals.Translated from Neorganicheskie Materialy, Vol. 40, No. 12, 2004, pp. 1418–1422.Original Russian Text Copyright © 2004 by Bodnar, Gremenok     

Pressure Effects on the Structural and Elastic Properties of AgGaS2–AgGaSe2Crystals: An X-ray Diffraction Study

The structural and elastic properties of AgGa(S_{1 – x} Se _x )₂crystals with the tetragonal chalcopyrite structure were studied by x-ray powder diffraction at pressures of up to 4 GPa. All of the crystals were found to have anisotropic elastic properties, with thec-axis compressibility notably exceeding the a-axis compressibility. The compression along the longer bond Ag–S(Se) is smaller than that along the Ga–S(Se). The compressibility anisotropy in the solid solutions and AgGaSe₂is stronger than that in AgGaS₂. The composition dependences of the elastic constants are nonlinear.     

Failure of Adhesive Bonds at Constant Strain Rates

Shear strengths of adhesive bonds using AF126 and two thicknesses of aluminum were measured at constant rate of crosshead separation. It was found that the shear strength could be related to temperature and strain rate or failure time over the range of deformation rates used.