EFFECT OF CS AND BA ADSORPTION ON THE ELECTRONIC-PROPERTIES OF CARBON-FILMS ADSORBED ON METALS (IR, RE)

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. © 1990.