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Abstract:
A preparation is reported which, for the first time, results in a thin, crystalline SiO2 film on a Mo(1 1 2) single crystal. The procedure consists of repeated cycles of Si deposition and subsequent oxidation, followed by a final annealing procedure. LEED pictures of high contrast show a crystalline SiO2 overlayer with a commensurate relationship to the Mo(1 1 2) substrate. Surface imperfections have been studied by SPA-LEED and a structure model, consistent with the appearance of antiphase domain boundaries as preferential disorder, is proposed. AES and XPS have been used to control film stoichiometry. A spatial dependence of the Si4+ core level shift with distance from the interface plane is observed and well explained by image charge interaction across the interface. Furthermore, the theoretically predicted insensitivity of the Si4+ core level shift with respect to the degree of crystallinity is experimentally verified for the first time. The wetting of the substrate by the film has been investigated by XPS and TDS. The results prove that the film covers the substrate completely.
