Results are reported of an investigation of the electrical properties of Ge films evaporated on Duran glass at different substrate temperatures TS. The resistivity measurements allow to distinguish between amorphous and polycrystalline films on account of a steep resistivity step of four or seven orders of magnitude at 294 or 80 K lattice temperature, respectively as found at TST = 135°C. This step is due to the fact that with the relatively high evaporation rate used, grains of only equal size are performed, and that with decreasing TS at TST all grains fall below a critical grain size. By the analysis of the lattice temperature dependence of the resistivity of the polycrystalline films, making use of the mean free path of carriers between two collisions at grain boundaries, the critical grain size was found to be about an elementary cell.
Interaction of Arsenious Oxide with DeNOx-Catalysts: An X-Ray Absorption and Diffuse Reflectance IR Spectroscopy Study. -The interaction of arsenious oxide (exposure via sublimation of As2O3 in air) with MoO3/TiO2 and WO3/TiO2 is studied by XANES and EXAFS and by in situ diffuse reflectance FT IR spectroscopy (DRIFT). The results indicate the formation of an orthoarsenate(V) species on the catalyst surface which interacts directly with tungsten sites. It is suggested that the poisoning of the WO3/TiO2 catalyst is due to blocking of active sites which involve coordinatively unsaturated tungsten centers by the orthoarsenate surface species. -(HILBRIG, F.; GOEBEL, H. E.; KNOEZINGER, H.; SCHMELZ, H.; LENGELER, B.; J.
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