Electronic structure of ultrathin Fe films onTiO2(110) studied with soft-x-ray photoelectron spectroscopy and resonant photoemission

We report on soft-x-ray photoelectron spectroscopy (SXPS) of a ${\mathrm{TiO}}_2$(110) surface during deposition of Fe in the monolayer regime. At low fractional monolayer coverages, the adsorbed Fe atoms are oxidized and Ti cations at the interface become reduced due to Fe adsorption. SXPS from shallow core levels and valence bands show that Fe starts to exhibit metallic character at a coverage of approximately 0.7 equivalent monolayers. Two well separated defect states appear in the band gap of ${\mathrm{TiO}}_2$ at iron coverages well below one monolayer. We use resonant photoemission to obtain information on the partial density of states, and we assign these defect states as being Fe-derived and Ti-derived states, located at the Fe and Ti sites, respectively. We suggest that a position change of oxygen is involved in the bonding of Fe on the ${\mathrm{TiO}}_2$(110) surface.