A photoemission and resonant photoemission study of Ba deposition at the TiO 110/surface

Results are reported on photoemission and resonant photoemission ResPES.measurements performed on a Ba-deposited TiO2 110.using synchrotron radiation. For coverages less than 1 monolayer ML.of Ba, only oxidized and no metallic Ba states were detected, and in the valence band spectra a new gap state, attributed to Ti3q, was seen at 0.8 eV below the Fermi edge and shown by ResPES to give a characteristic 3pª3d resonance of Ti. When the Ba thickness exceeds 1 ML, a resonance of the near-Fermi-edge bandgap state appears, with a maximum found for the Ba 4dª4f resonant transition. The metallic nature of the layers thicker than 1 ML is confirmed by an asymmetry of the Ba 4d peak. Work function measurements showed an abrupt change with Ba thickness when approaching 1 ML, in consistence with the above results. q1999 Elsevier Science B.V. All rights reserved