Influence of CO admolecules on the electronic state of ytterbium nanofilms grown on silicon substrates

The adsorption of carbon monoxide (CO) molecules on ytterbium nanofilms from 16 to 200 monolayers thick (61–76 nm) has been studied. The films have been grown on single-crystal Si(111) substrates. It has been shown that before CO molecule adsorption, ytterbium is in the divalent state with electronic configuration [Xe]4$f^{14}$6$s^{2}$. After gas molecule adsorption, a layer of trivalent ytterbium (electronic configuration [Xe]4$f^{13}$5$d^{1}$6$s^{2}$) forms in a part of the film that is adjacent to the surface. The thickness of the layer modified by CO admolecules has been estimated. It has been found that the thickness is within 9–22 monolayers (3.4–8.4 nm).