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Chemically inert coatings on Havar ® entrance foils of the targets for [ 18 F] production via proton irradiation of enriched water at pressurized conditions are needed to decrease the amount of ionic contaminants released from Havar ® . During current investigation, magnetron sputtered niobium and niobium oxide were chosen as the candidates for protective coatings because of their superior chemical resistance. Aluminated quartz substrates allowed us to verify the protection efficiency of the desirable coatings as diffusion barriers. Two modeling corrosion tests based on the extreme susceptibility of aluminum to liquid gallium and acid corrosion were applied. As far as niobium coatings obtained by magnetron sputtering are columnar, the grain boundaries provide a fast diffusion path for active species of corrosive media to penetrate and to corrode the substrate. Amorphous niobium oxide films obtained by reactive magnetron sputtering showed superior barrier properties according to the corrosion tests performed. In order to prevent degrading of brittle niobium oxide at high pressures, multilayers combining high ductility of niobium with superior diffusion barrier efficiency of niobium oxide were proposed. The intercalation of niobium oxide interlayers was proved to interrupt the columnar grain growth of niobium during sputtering, resulting in improved diffusion barrier efficiency of obtained multilayers. The thin layer multilayer coating architecture with 70 nm bi-layer thickness was found preferential because of higher thermal stability. [ABSTRACT FROM AUTHOR]

Hydrogenated intrinsic amorphous silicon (a-Si:H) was investigated as a surface passivation method for crystalline silicon thin film solar cells on graphite substrates. The results of the experiments, including quantum efficiency and current density–voltage measurements, show improvements in cell performance. This improvement is due to surface passivation by an a-Si:H( i ) layer, which increases the open circuit voltage and the fill factor. In comparison with our previous work, we have achieved an increase of 0.6% absolute cell efficiency for a 40 μm thick 4 cm 2 aperture area on the graphite substrate. The optical properties of the SiN x /a-Si:H( i ) stack were studied using spectroscopic ellipsometer techniques. Scanning transmission electron microscopy inside a scanning electron microscope was applied to characterize the cross section of the SiN x /a-Si:H( i ) stack using focus ion beam preparation. [ABSTRACT FROM AUTHOR]

Abstract: Poly- and single-crystal thin films of U–Mo alloys have been grown both on glass and sapphire substrates by ultra-high vacuum magnetron sputtering. X-ray and Electron Backscatter Diffraction data indicate that for single-crystal U1− x Mo x alloys, the pure cubic uranium γ-phase exists for x ≥0.22 (10wt.% Mo). Below 10wt.% Mo concentration, the resulting thin film alloys exhibited a mixed α–γ uranium phase composition. [Copyright &y& Elsevier]

Abstract: Tribofilms, formed by tribochemical reactions between steel surface and trimethylphosphite in gas phase, have been characterized by various structural and analytical techniques including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS). Focus ion beam technique has been used to prepare cross-sections of the tribofilm for further TEM and EDS analyses. Cross-sectional views of tribofilms obtained by gas phase lubrication show that tribofilm has an inhomogeneous thickness ranging from 10 to 50nm and is amorphous. Complementary XPS and EDS analyses confirm the formation of various iron phosphides as the major component of the tribofilms, with a preferential nucleation of Fe3P stoichiometry at the interface between steel and tribofilm. [Copyright &y& Elsevier]