CORE-LEVEL X-RAY PHOTOELECTRON-SPECTRA AND X-RAY PHOTOELECTRON DIFFRACTION OF RUO2(110) GROWN BY MOLECULAR-BEAM EPITAXY ON TIO2(110)

We have measured Ru 3d, 4s, 4p and O Is high-resolution core-level X-r ay photoelectron spectra, along with Ru 3d and O Is scanned-angle X-ra y photoelectron diffraction angular distributions, for RuO2(110). The surfaces were prepared by oxygen-plasma-assisted molecular beam epitax ial growth of RuO2 on TiO2(110). XPS spectral interpretation and the n ature of the XPD scans strongly suggest that the complex line shapes a re due to final-state screening effects, rather than the presence of R u in oxidation states other than +4. (C) 1997 Elsevier Science B.V.