THERMAL-STABILITY OF PT FILMS ON TIO2(110) - EVIDENCE FOR ENCAPSULATION

We have studied the thermal stability of ultrathin platinum films on a rutile TiO2(110) surface, using low energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS). At room temperature, Pt grows in three-dimensional islands on the TiO2 surface, with little indication of an interface reaction. Upon annealing to temperatures above 450 K in UHV, encapsulation of the Pt islands by Ti suboxides is observed; the rate of this process increases with annealing temperature and decreases with island thickness. The Ti layer on top of the Pt islands is identified as a reduced Ti-n+ species (1 less than or equal to n less than or equal to 3) with the degree of reduction depending on the thickness of the Pt islands. These results are discussed in the framework of the strong metal-support interaction (SMSI) effect.