Modification of the surface and bulk electronic properties of ytterbium nanofilms under the action of adsorbed CO molecules

The modification of the surface and bulk electronic properties of ytterbium nanofilms under the action of adsorbed CO molecules has been investigated. It has been shown that adsorption of these molecules is accompanied by a fundamental rearrangement of the electronic structure of the films. This rearrangement is initiated by the formation of a donor-acceptor adsorption bond by a lone electron pair localized at the carbon atom of the CO molecule. The formation of this bond is accompanied by the lowering of the Yb 5$d$ level below the Fermi level. After this lowering reaches a considerable value, the 4$f$ electrons start to transfer to the 5$d$ level; i.e., the 4$f^{14}$ $\to$ 4$f^{13}$ transition occurs. The transition opens a way to the $N_{45}N_{67}N_{67}$ Koster–Kronig supertransition in the Auger spectra. As a result of these processes, the peaks observed in the spectra before adsorption of the CO molecules disappear and new peaks appear. Therefore, the adsorption of the CO molecules brings about qualitative changes in the Auger spectra of ytterbium. It has been found that the rearrangement of the ytterbium electronic structure due to the action of CO molecules involves both the surface of the ytterbium films and their near-surface layers. The thickness of these layers exceeds the Auger electron escape depth and can reach more than 11 monolayers.