Effect of Cs and Ba adsorption on the electronic properties of carbon films adsorbed on metals (Ir, Re)

Abstract

The effect of adsorption of cesium, barium and oxygen on the electronic properties of mono- and multilayer carbon films on the surface of metals (Ir, Re) has been studied by high resolution (Δ E E ≈0.1%) Auger electron spectroscopy. The shape of the high-energy part of the carbon Auger spectrum has been found to change dramatically after the adsorption of Cs and Ba atoms on a monolayer of graphite film on metals. This change is similar to the effect observed on single crystal intercalated by donor atoms. The reason for the close electronic properties between a graphite layer adsorbed on a metal surface and that representing a part of a macroscopic graphite crystal is that the graphite film is separated from the metal surface at a distance characteristic of the van der Waals forces. This effect was not observed in the adsorption of Cs and Ba atoms on a film of chemisorbed carbon on metals, which does not exhibit a graphite structure. Oxidation of the Cs or Ba adsorbed on a graphite layer on a metal has been shown to affect the direction of the electron exchange by restoring the electrons from the graphite valence band to the adparticles.