INITIAL-STAGES OF FE(110) OXIDATION AT 300 K - KINETICS AND STRUCTURE

STM has been used to study the structural changes occurring during O-2 chemisorption on Fe(110) and to correlate these with sticking and LEE D measurements [A. Hodgson et al., Surf. Sci. 319 (1994) 119]. Oxygen forms an ordered c(2 X 2) phase with a coverage of 0.25 monolayer whic h at higher coverages is replaced by a disordered layer with local fea tures having a (3 x 1) periodicity, aligned to the close packed direct ions. At O coverages above similar to 0.25 monolayer the surface shows small single step height features on the O-rich areas of the surface, attributed to FeO. As the O coverage increases above 0.4 monolayer th e size and density of the FeO islands increases, finally giving a hexa gonal LEED pattern characteristic of FeO(111). The onset of FeO nuclea tion coincides with a minimum in the O-2 sticking probability.