3D-Atom-probe study of oxygen-adsorption on stepped platinum surfaces

Oxygen adsorbed on Pt (011), (012) and (113) has been studied by means of field desorption in a three-dimensional atom-probe. The formal procedure of these experiments is quite similar to thermal desorption. Comprehensive investigations with the thermal desorption technique report on a highly stable atomic oxygen phase on Pt, which has been attributed to a subsurface oxygen layer or platinum oxide. In atom-probe depth profiling experiments oxygen was measured only in the topmost layer. Oxygen and platinum have been detected almost as single atomic ions, Pt-oxygen complexes have not been observed in the time-of-flight mass spectra. The 2D plots of the impact positions of the desorbed ions as well as field ion micrographs show most of the oxygen adsorbed in highly co-ordinated sites on the (012) and (113) planes.