Surface morphology of Au(111) after exposure to oxygen at high temperature and pressure

We report a scanning tunnelling microscopy (STM) study of the surface morphology of Au(111) exposed to oxygen at high temperature (700-800 degrees C) and high pressure (1 bar). Two types of oxygen induced surface structures were observed: (i) a hexagonal long-range reconstruction [L. Huang et al., Appl. Phys, Lett. 66 (1995) 211] with a periodicity of similar to 65 Angstrom and a corrugation of about 0.5 Angstrom. At the atomic scale this surface exhibits a (root 3 X root 3)R30 degrees structure, which we attribute to atomic oxygen strongly chemisorbed at the Au(111) surface. (ii) a ''modified'' herringbone pattern related to the original herringbone reconstruction of the clean Au(111) surface, but with additional depressions in some of the fee-regions between the reconstruction lines. At the atomic scale this surface exhibits a characteristic ''row structure'' with root 3 periodicity. For both structures the dependence of the STM image contrast on the tunnelling parameters was investigated.