SURFACE PRECIPITATION PROCESS OF EPITAXIALLY GROWN GRAPHITE (0001) LAYERS ON CARBON-DOPED NICKEL(111) SURFACE

The surface precipitation process of epitaxially grown graphite (0001) layers on the C-doped Ni(111) surface has been investigated by in situ x-ray photoemission spectroscopy measurements. Peak intensity measurements at various temperatures clarified the change of the carbon chemical state from the segregated carbon through the monolayer graphite to the multilayer graphite. The simple thickness estimation in the transition region from the monolayer graphite to the multilayer graphite indicates that once the estimated thickness is calibrated, controlling the thickness of the graphite thin film in the monolayer range by a precise adjustment of the temperature may be possible. Changes of the chemical states of carbon on the Ni(111) surface with temperature were clarified by high-resolution measurements with a monochromated Al Kalpha source. From the observed chemical shift of the C 1s peaks, a negative charge transfer from the monolayer graphite to the substrate can be postulated. This C-Ni interaction is considered to be the possible cause for the stability of the monolayer graphite over 100 K.