Preparation of epitaxial ultrathin RuO2-TiO2(110) films by decomposition of Ru3(CO)12

Ru-3(CO)(12) has been used as a source for depositing metallic ruthenium particles and RuO2 films over a TiO2(110) surface. At 300 degrees C in ultrahigh Vacuum the precursor is completely decomposed, and the deposited metal particles show some residual carbon contamination. Such a deposit is disordered, both in the short and long range, and the high binding energy found for the metal suggests the presence of nano-clusters on the surface. The Ru-TiO2 interface seems to be non-reactive, in the sense that the titanium atoms of the substrate are not reduced by reaction with the incoming metal atoms. On the other hand, RuO2 ultrathin epitaxial films are easily obtained either by heating the metal deposit at 300 degrees C or by directly decomposing the organometallic precursor in an oxygen atmosphere (2 x 10(-6) mbar). These films grow in a three-dimensional cluster-like way and are epitaxial, as demonstrated by the presence of well-defined X-ray photoelectron diffraction patterns. The new RuO2-TiO2 interface is, on the contrary, reactive and there is some evidence for the presence of some charge transfer from the electron-rich RuO2 toward the electron-poor TiO2. (C) 1999 Elsevier Science B.V. All rights reserved.