Comparative study of annealing effects for Cu/Pt(1 1 1) films with and without oxygen

The effect of annealing on Cu/Pt(1 1 1) films with and without oxygen has been studied by low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), and ultraviolet photoelectron spectroscopy (UPS). While the first Cu layer on bare Pt(1 1 1) grows pseudomorphically the second layer grows epitaxial and rotationally commensurate to the Pt(1 1 1) substrate. Only after a 1.2 ML Cu/Pt(1 1 1) film was annealed at temperatures above 600 K, the (1×1) structure was observed indicating alloy formation. After exposing the 1.2 ML Cu/Pt(1 1 1) system to 12 L O2 at 320 K, no new LEED features were observed. Annealing of this system at temperatures between 600 and 700 K causes a 2×2 structure to emerge. AES and UPS measurements suggest the co-existence of a copper oxide at a Cu–Pt alloy. At higher temperatures, the copper adatoms diffuse into the Pt(1 1 1) substrate to form an alloy while the oxygen desorbs.