Effects of H-termination on initial oxidation process

The initial oxidation processes of H-terminated Si(100) surfaces have been investigated by means of high-resolution electron energy loss spectroscopy. The adsorption of atomic oxygen on H-terminated Si(100) surfaces occurs even at room temperature and there exist two steps in the initial oxidation of H-terminated surfaces at oxidation temperatures below 300°C, in contrast with the oxidation of clean surfaces: Oxygen atoms preferentially adsorb on one of the two back-bond sites of a surface Si atom until an oxygen coverage is 0.8 and the other sites such as the other back-bond sites are occupied by oxygen atoms above 0.8. This coverage is very close to the saturation coverage of oxygen atom adsorption when oxygen atoms are forbidden to adsorb on the back-bond sites adjacent to an oxygen-occupied site, which is confirmed by the simulation results. Moreover, the existence of SiH bonds is considered to promote the structural relaxation of SiOSi bonds.