Quantum chemical study of adsorption and dissociation of HfCI_4 and H2O on Ge/Si(100) - (2x1): Initial stage of atomic layer deposition of HfO_2 on SiGe surface

摘要

We investigated adsorption and dissociation of water and HfCl_4 on a Ge/Si(100) -(2X1) surface with a density-functional theory. The Si-Ge and Ge-Ge homodimers are used to represent the Si_(1-x)-Ge_x surface, (i) Water first adsorbs on the bare Ge/Si(100) - (2 X 1) surface and then dissociates into OH and H. The activation energy for adsorption of water on the Ge-Ge homodimer is much higher than that on the Si-Ge heterodimer. (ii) HfCl_4 dissociates upon adsorption on the Ge/Si(100) -(2X1) surface into HfCl_3 and Cl. No net activation barrier exists during the adsorption of HfCl_4 on both SiGe surface dimers. The molecular adsorption state is found to be metastable according to the calculation, which implies that the reaction tends to move toward to the product rather than trapping in HfCl_4 adsorbed state. The difference in the potential energy surface between reactions on Si-Ge and Ge-Ge dimers is due to different bond strengths.