EPITAXIAL-GROWTH OF ULTRATHIN FILMS OF CHROMIUM AND ITS OXIDES ON PT(111)

The growth of vapor-deposited Cr and chromium oxide on Pt(111) has bee n studied by ion scattering spectroscopy, x-ray photoelectron spectros copy, low energy electron diffraction, and scanning tunneling microsco py. Both metal Cr film and its oxide nucleate at Pt(111) step edges, a nd grow in a step-flow mode. The metal Cr film is pseudomorphic to the Pt(111) substrate within the first two monolayers. At higher coverage s, the chromium overlayer adopts a bcc(110) surface structure and form s three-dimensional elongated islands oriented along the three close-p acked directions of the Pt(111) surface. For the chromium oxide, a wel l ordered p(2X2) structure is observed within the first two monolayers and attributed to the epitaxial growth of metastable Cr3O4. At higher coverages, a (root 3 X root 3)R30 degrees structure appears, due to t he formation of the stable Cr2O3 phase. (C) 1997 American Vacuum Socie ty.