Initial oxidation and surface stability diagram of Ge(100) as a function of the temperature and oxygen partial pressure through ab initio thermodynamics

Abstract

Density functional theory calculations in conjunction with thermodynamic modeling were performed to examine the oxygen adsorption on a Ge(100) c(4 x 2) surface and the subsequent initial oxidation. For several possible adsorption sites, the adsorption energy of atomic oxygen as well as the atomic configuration and electronic properties of the adsorbed structure were examined. Then the effects of the surface coverage of oxygen from 1/64 to 1/4 monolayers on the adsorption energy were considered. Through the surface Gibbs free energy as a function of the temperature (T) and oxygen partial pressure (P-O2), the (T, P-O2) surface stability diagram was predicted for the O/Ge(100) c(4 x 2) surface. The theoretical prediction well reproduced previous experimental observations and provides an insight to control the initial oxidation process of Ge surface with tuned T and P-O2.