TiNxOy films were prepared by activated reactive evaporation (ARE) on copper to produce a tandem solar absorber exhibiting a low emissivity (epsilon) (250 degree(s)C) 2/PO2) gas pressure ratios, show that maximum (epsilon) is obtained when the ratio PN2/PO2 is held approximately equals eight. The chemical composition of these TiNxOy films was determined by x-ray photoelectron spectroscopy (XPS) and related to solar selective properties. The investigated samples consist of about 38 - 42 atomic % titanium, 35 - 37 at% oxygen and 21 - 23 at% nitrogen (bulk values), depending on preparation conditions. A depth profile indicates an oxygen enrichment at the surface, partially due to the exposure of the samples to atmosphere. After sputtering the photoelectron spectra show a marked peak at the TiO and TiN positions and a weaker one at the TiO2 position. Therefore, with regard to the known composition, the film is mainly a TiO(-N) compound with a small admixture of TiO2. The surface layer is almost entirely consisting of TiO2. Additionally, there might also be a small amount of TiC (3 at% carbon impurity was detected).
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