XPS and factor analysis for investigation of sputter-cleaned surfaces of metal (Re, Ir, Cr)–silicon thin films

XPS and factor analysis were used for investigation of the electronic structure of MexSi1−x (Me=Re, Ir or Cr) thin films which show a semiconductor-to-metal transition at a critical (metal) concentration xc. Sputter cleaning applied for surface preparation leads to enrichment of Me and, as proved by TEM investigations, to silicide formation. For RexSi1−x and IrxSi1−x films, this influences the XPS valence band and the core level spectra, signals of silicide bonding are extracted and their contributions to the XPS data are quantified by factor analysis. On that way, an indirect connection to xc for RexSi1−x films is found by quantification of metallic Re contributions. For the CrxSi1−x films, valence band studies are more promising, energy shifts of the valence band edge correlate with the electrical transport properties.