THE GROWTH OF THIN TI AND TIOX FILMS ON PT(111) - MORPHOLOGY AND OXIDATION-STATES

The initial stages of the growth of Ti and TiO(x) films on Pt(111), grown by evaporation in ultra-high vacuum or under controlled pressure of oxygen, has been studied using X-ray absorption fine structure (XAFS) taken above the Ti K-edge, and by ion scattering and X-ray photoelectron spectroscopy. Extended XAFS spectra of the metallic films reveal that growth occurs from the earliest stages as islands. Analysis of the EXAFS amplitudes and the low-energy ion scattering data indicate that the islands retain a morphology in which the thickness and lateral extent are similar as they coarsen through continued growth. Room-temperature oxidation of these metallic films leads to mixed oxidation states, but evaporation in oxygen atmospheres allows films of higher, and more homogeneous, oxidation state to be prepared, as judged by near-edge XAFS and Ti2p level photoemission.