SURFACE DEFECT CHARACTERIZATION IN OXYGEN-DOSED NICKEL SURFACES AND IN NIO THIN-FILMS BY CO ADSORPTION-DESORPTION EXPERIMENTS

Oxygen-covered Ni(110) as well as thin NiO films grown by oxidation of that surface were characterized under ultrahigh vacuum by using low-e nergy electron diffraction (LEED), X-ray photoelectron (XPS), Auger (A ES), and ion scattering (ISS) spectroscopies together with CO temperat ure-programmed desorption (TPD) titrations. Results from NiO(100) film s with surface defects induced via Ar+ ion irradiation at room tempera ture were compared with those from partially oxidized ordered Ni(110) surfaces. CO TPD proved to be a useful local probe for the investigati on of defective NiO surfaces, since its adsorption energy varies by ov er 20 kcal/mol in going from a metallic Ni(110) clean surface to NiO. The CO-probing experiments also revealed that Ar+ bombardment of thin NiO films leads to the formation of Ni-O phases similar to those found during the early oxidation stages of the Ni metal surface.