Structure evolution for annealing Co ultrathin films on Pt (111)

Low-energy electron diffraction (LEED), Auger electron spectroscopy (AES) and ultraviolet photelectron spectroscopy (UPS) were used to study the thermal evolution of the structure of cobalt ultrathin films on a Pt(111) surface at different coverages. The phase diagram of surface structures was obtained from LEED observation. Several structural phases of this system were observed, i.e. pseudo-(1 × 1), incoherent epitaxy, extra p(2 × 2), rotational incoherent epitaxy, and alloying (1 × 1) structures. The coverage and temperature ranges were examined for each structure. Alloy formation was verified by AES. The changes in valence-band structures during phase transitions were studied by UPS.