ULTRAHIGH-VACUUM SCANNING TUNNELING MICROSCOPY STUDIES OF PLATINUM ONGRAPHITE

The surface morphology of submonolayer coverages of platinum vapor dep osited onto highly oriented pyrolytic graphite (HOPG) has been studied . With coverages of 5%-30% of a monolayer, we have observed both three -dimensional clusters and two-dimensional (2D) islands of Pt on the su bstrate. Our studies concentrated on the 2D islands of Pt, which exhib ited several interesting features. Small islands exhibited epitaxial g rowth on the HOPG with markedly small Pt-Pt bond lengths, as well as o ccasional features of larger spacings. Similar larger structures on gr aphite islands and near graphite steps on the clean HOPG surface were observed. Results of scanning tunneling spectroscopy show that spectra on platinum deposits exhibit a broader character than those on clean graphite and show some structure consistent with bulk Pt.