O(2) dissociation before the onset of added row nucleation on Ag(110): an atomistic scanning tunnelling microscopy...

We present here a scanning tunnelling microscopy (STM) study on O(2) adsorption at Ag(110) at T = 175 K, i.e. in the temperature range between the onset of O(2) dissociation and the formation of the added row reconstruction. In agreement with previous studies at lower surface coverage, we observe several structures forming upon O(2) dissociation, including Ag-O complexes randomly distributed on the surface. We suggest that the presence of the latter structures, characterized by a large cross section for low energy electrons, can account for the marked decrease of the surface electron reflectivity and for the corresponding increase of the diffuse elastic intensity previously reported in a HREELS investigation of the same system.