The interaction of oxygen with the clean (1 × 1) surfaces of Cr(100) and Cr(100) single crystals has been examined by LEED, XPS, AES and Δφ measurements. At low exposures, oxygen on both surfaces is found to form metastable overlayers at 300 K which slowly undergo incorporation into the underlying metal with a characteristic half-life of several minutes. At higher exposures (10-100 L), formation of Cr2O3 films takes place; the rate of corrosion is demonstrated to be structure sensitive, film thicknesses of 0.4 and 1.3 nm being observed after 100 L O2 exposures on Cr(100) and Cr(100) respectively. The oxide on Cr(100) was found to adopt a well-ordered c(2 × 4) structure, whereas Cr(110) exhibited oxygen-induced faceting. The results are discussed in the light of previously reported studies of these chemisorption systems. © 1985.
