AN IN-SITU XPS STUDY OF SPUTTER-DEPOSITED ALUMINUM THIN-FILMS ON GRAPHITE

Interfaces created by sputter deposition of aluminium on the basal pla ne of highly oriented pyrolytic graphite (HOPG) have been investigated in situ by X-ray photoelectron spectroscopy (XPS). Chemical bonds hav e been characterized by well defined chemical states in the Al2p and C 1s photoelectron peaks displaying chemical shifts of + 1.2 +/- 0.1 eV for Al2p and - 2.1 +/- 0.1 eV for C1s with respect to bulk aluminium a nd graphite, respectively. This reveals the existence of a marked char ge transfer from aluminium to carbon with the formation of carbide-lik e species. The growth mode of the film has been described with an earl y stage of aluminium cluster formation involving Al-C bonds at the int erface, followed by the growth of a pure aluminium overlayer. The inte rfacial carbide-like component Al(x)C with x almost-equal-to 1.4 exten ds to about 18 angstrom in the film.