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

Abstract

The interactions of hyperthermal chlorotitanium ions, TiClx+ (x = 0−4) with HOPG surfaces were studied by low-energy ion scattering of TiClx+ from HOPG and by XPS depth profile analysis of the TiClx+ exposed HOPG surfaces. Positive ion scattering data for 5−500 eV collision energies showed exclusively dissociative scattering of the molecular TiClx+ into TiCl+ and Ti+ fragments. TiCl3+ and TiCl2+ daughter fragments were not detected in the surface-induced dissociation (SID) spectra of the corresponding larger incident TiClx+ ions. The observed survival of >100 eV TiCl3+ and TiCl2+ incident ions in the scattered ion spectra and the calculated trend in the electron affinities of TiClx neutrals implicate the role of bond dissociation in the efficient electron transfer to the departing TiCl3 and TiCl2 fragments during SID. XPS depth profile analysis showed a good correlation between the collision energy and the type of incident TiClx+ 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 TiClx+ ion gave lower stoichiometries and lower carbidization efficiencies in the resulting films.