Theoretical investigation on the adsorption and dissociation behaviors of TiCl ₄ on pyrolytic carbon surface

We present a theoretical investigation of the reaction mechanism of TiCl ₄ dissociation on pyrolytic carbon surface and discuss the influence of H atom on adsorption and dissociation behaviors of TiCl ₄ by using density functional theory. The adsorption behaviors of TiCl _x (x = 4-0) and the interactions between pre-adsorbed H atom and TiCl _x are studied by calculating adsorption energies E _ads and interaction energies H _Ti , respectively. The pre-adsorbed H atom significantly facilitates the adsorption of TiCl _x on pyrolytic carbon surface. Specially, TiCl ₃ adsorption on pyrolytic carbon surface converts from an endothermic process into an exothermic process due to the present of pre-adsorbed H atom. The calculation results of H _Ti show that the interactions between pre-adsorbed H atom and TiCl _x are attractive. The dissociation of TiCl ₄ on pre-adsorbed H pyrolytic carbon surface is an exothermic process, and TiCl ₄ → TiCl ₃ is the limited step. The dissociation barriers of each step are less than 1.5 eV except for TiCl → Ti, which does not need to overcome any barriers, that is to say, once TiCl is adsorbed on pre-adsorbed H surface the reaction of TiCl → Ti spontaneously occurs. It thus can be concluded that the dissociation of TiCl ₄ on pyrolytic carbon surface is a favorable process as long as H ₂ molecular have decomposed into atomic H and adsorbed on pyrolytic carbon surface, and the intermediate species (TiCl ₃ , TiCl ₂ and TiCl) play an important role on the titanium CVD deposition. We also study the adsorption behavior of H atom and the dissociation behavior of H ₂ molecular on pyrolytic carbon surface.