X-RAY PHOTOELECTRON-SPECTROSCOPY CHARACTERIZATION OF HIGH-DOSE CARBON-IMPLANTED REFRACTORY-METALS

A study has been made of the depth dependence of atomic fraction and chemical bonding states of carbon-implanted group IVa to VIa transition metals, by means of X-ray photoelectron spectroscopy combined with an Ar+ sputtering. Implantation of C-12+ was performed with 10(18) ions cm-2 at 100 keV, and at room temperature. A gaussian-like carbon distribution, predicted by the range theory, was observed even following such a very high dose. The implanted carbon combined with both matrix metal and carbon itself to form metallic carbides and graphitic solid state carbon. The carbon-enriched carbides were also found by the deconvolution of C Is spectra. The depth profile of C-metal bonded carbon was trapezoidal, whereas C-C bonded carbon exhibited a gaussian profile corresponding to the net carbon distribution. The binding energy of core electrons of metals shifted nearly linearly with carbon content at the region deeper than the average projected range and at the shallower region it was large and approximately constant, which indicate the formation of carbides with carbon vacancies and stoichiometric carbides respectively. These results will be discussed with respect to the energy deposition effects accompanied by ion implantation.