GROWTH AND STRUCTURE OF ULTRATHIN CR FILMS ON PT(111)

The growth and structure of ultrathin chromium films on Pt(111) have b een studied using low-energy He+ ion scattering spectroscopy, X-ray ph otoelectron spectroscopy, low energy electron diffraction and scanning tunneling microscopy. Upon initial deposition at room temperature, th e Cr atoms migrate along the Pt terraces and populate the step edges. Further growth results in two-dimensional islands of chromium developi ng from the step edges and across the Pt terraces. The him is pseudomo rphic to the Pt(111) substrate. At coverages above 3 ML, chromium form s three-dimensional elongated islands oriented along the three close-p acked directions of the Pt(111) surface. The chromium overlayer adopts a bcc (110) surface structure with the close-packed overlayer directi ons, [111], aligned with the close-packed Pt(111) directions, [110]. T he presence of the Cr overlayer was found to electronically perturb th e Pt surface atoms leading to a redistribution of charge between Pt an d Cr.