Real time scanning tunneling microscopy study of the initial stages of oxidation of Ni(111) between 400 and 470 K

A real-time in situ study of the initial stages of the interaction of oxyge n with Ni(111) in a high temperature scanning tunneling microscope (STM) at temperatures between 400 and 470 K is presented. Oxygen adsorption feature s, in particular the Ni(111)-p(2X2)O reconstruction, were identified in roo m temperature STM images. The process of oxide formation is investigated in detail at 470 K. Starting from the initial nucleation at the step edges, a gradual transformation of the terrace structure results in the formation o f a three-domain NiO(001) layer finally covering: the entire terraces as we ll as forming bulges at the steps due to surface diffusion of excess Ni. We ll-resolved local oxide surface structures are discussed on the basis of a thin (001)-oriented NiO layer model on the Ni(111) substrate. Formation of triangular bulk NiO(111) islands is observed for higher oxygen exposures ab ove 25 L. (C) 2000 American Vacuum Society. [S0734-2101(00)00203-7].