Low-temperature grown single-crystal Si on epi Ge(001)-2 × 1 and its oxidation: electronic structure study via synchrotron radiation photoemission

The capped Si expels completely the Ge dimers on top of the epi Ge(001)-2 × 1 and exhibits a multiphase electronic structure consisting of strained surface atoms bonded with Ge in the film. The deposition of molecular oxygen at room temperature removes a portion of the segregated Ge atoms and oxidizes some of the rest. The surface Si atoms exhibit 1+ to 4+ charge states. Heat eliminates the embedded Ge in the capped Si film and transfers the oxygen bonded with the surface Ge to Si. The oxidation reactions occur primarily on the capped Si surface region without involving the Si/Ge interface.