Interactions of Hyperthermal TiClx+ (x = 0−4) Ions with Graphite Surfaces

The interactions of hyperthermal chlorotitanium ions, TiCl x + ( x = 0−4) with HOPG surfaces were studied by low-energy ion scattering of TiCl x + from HOPG and by XPS depth profile analysis of the TiCl x + exposed HOPG surfaces. Positive ion scattering data for 5−500 eV collision energies showed exclusively dissociative scattering of the molecular TiCl x + into TiCl + and Ti + fragments. TiCl 3 + and TiCl 2 + daughter fragments were not detected in the surface-induced dissociation (SID) spectra of the corresponding larger incident TiCl x + ions. The observed survival of >100 eV TiCl 3 + and TiCl 2 + incident ions in the scattered ion spectra and the calculated trend in the electron affinities of TiCl x neutrals implicate the role of bond dissociation in the efficient electron transfer to the departing TiCl 3 and TiCl 2 fragments during SID. XPS depth profile analysis showed a good correlation between the collision energy and the type of incident TiCl x + with the quality of TiC thin films formed on the surface of HOPG. Higher collision energies resulted in higher carbidic C to Ti ratios and higher carbidization efficiencies whereas a larger number of Cl atoms in the incident TiCl x + ion gave lower stoichiometries and lower carbidization efficiencies in the resulting films.