In-situ monitoring of oxygen adsorption at Mo(112) surface via fast atom diffraction

The adsorption of oxygen on a Mo(112) surface is studied via scattering of fast He atoms under a grazing angle of incidence. We show that, in addition to the intensity for reflected atoms, diffraction effects for fast atoms can be used to monitor adsorption and to obtain also information on the unit cell of adsorbed atoms. The new method is demonstrated by studies on oxygen exposure where as a function of O2 dose and target temperature a variety of superstructures can be found. Our conclusions are supported by work performed with LEED.