X-ray photoelectron spectroscopy study of TiC films grown by annealing thin Ti films on graphite

Abstract

Thin Ti films with thicknesses in the range between 200 and 300 Å were evaporated onto graphite substrates under UHV conditions. The samples were annealed up to temperatures of 1470 K. After reaching steady state, subsequent x-ray photoelectron spectroscopy analysis showed formation of different TiCx phases dependent on the annealing temperature. For temperatures lower than 600 K, little carbide formation occurs in the metal film; a mixed metal–carbide phase forms only at the metal–graphite interface. At higher temperatures, the concentration ratio x of carbidic C to Ti ranges from about 0.6 at 750 K to about 0.95 at 1200 K and higher annealing temperatures. It was observed that the binding energies of the Ti 2p electrons rise continuously with increasing concentration ratio of carbidic C to Ti. Depth profiles were made to investigate chemical phases in the Ti film, as well as at the interface. It is illustrated from the profiles that formation of carbide proceeds from the metal–graphite interface, as well as from surface segregated carbon and advances into the Ti layer from both sides.