Effect of Interfacial Sulfur on Oxidation Behavior and Oxide Adhesion to Fe(111)

Abstract

We report the first STM observations of the thermally induced dewetting of an iron oxide scale from an Fe(111) surface. In addition, we report the influence of the presence of S at the metal/oxide interface on substrate topography. Room-temperature oxidation of S-free and (1 × 1)-S-covered Fe(111) surfaces at oxygen partial pressures of 1 × 10-7 to 5 × 10-7 Torr resulted in the growth of oxide islands, with the only difference being the formation of larger islands in the latter case. Line shape analyses of the Fe(MVV) peak indicated a similar growth mechanism in both cases, with the formation of Fe3O4 initially and Fe2O3 at higher exposures of O2. Flash annealing of the oxide formed on the S-free and (1 × 1)-S-covered surfaces in ultrahigh vacuum (UHV) resulted in oxide dewetting, leaving larger oxide islands separated by S-free or S-covered Fe regions, respectively. The presence of S at the metal/oxide interface causes oxide dewetting to occur at lower temperatures than those on a S-free surface. In the ...