Comparative study of annealing effects for Cu/Pt(111) films with and without oxygen

The effect of annealing on Cu/Pt(111) films with and without oxygen has bee n studied by low-energy electron diffraction (LEED), Auger electron spectro scopy (AES), and ultraviolet photoelectron spectroscopy (UPS). While the fi rst Cu layer on bare Pt(111) grows pseudomorphically the second layer grows epitaxial and rotationally commensurate to the Pt(111) substrate. Only aft er a 1.2 ML Cu/Pt(111) film was annealed at temperatures above 600 K, the ( 1 x 1) structure was observed indicating alloy formation. After exposing th e 1.2 ML Cu/Pt(111) system to 12 L O-2 at 320 K, no new LEED features were observed. Annealing of this system at temperatures between 600 and 700 K ca uses a 2 x 2 structure to emerge. AES and UPS measurements suggest the co-e xistence of a copper oxide at a Cu-Pt alloy. At higher temperatures, the co pper adatoms diffuse into the Pt(111) substrate to form an alloy while the oxygen desorbs. (C) 2001 Elsevier Science B.V. All rights reserved.