Effect of adsorbed oxygen on the properties of ytterbium nanofilms

The effect of O$_2$ molecules adsorbed on the surface of ytterbium nanofilms on the properties of the volume and surface of these films has been studied. It has been shown that the dependence of the work function of the films on the concentration of O$_2$ adsorbed molecules exhibits a nonmonotonic behavior: originally, the work function decreases, to start increasing again on passing through a minimum. At high oxygen doses, this increase stops. Adsorption of oxygen brings about a fundamental rearrangement of the Auger spectra of ytterbium; indeed, the Auger peaks observed before oxygen adsorption disappear completely after its deposition on the surface, to become replaced by other ones. The results obtained qualitatively agree with similar observations amassed by the present authors in studies of adsorption of CO molecules on the surface of ytterbium films. These results should be ascribed to a manifestation of complex processes of electron exchange between these films and adsorbed O$_2$ molecules. These processes end up in a qualitative rearrangement of the electronic structure of the part of film volume that borders the surface, where ytterbium transforms into the $d$ metal.