Formation of oxygen-induced Si(1 1 3)-3 × 2 facets on the Si(5 5 12) surface

We report the formation of Si(1 1 3)-3 × 2 facets upon exposing oxygens on the Si(5 5 12) surface at an elevated temperature. These facets are found to form only for a limited range of oxygen exposure and exhibit a well-defined 3 × 2 LEED pattern. We also find the surface electronic state unique only to the facets in the valence band. The spectral feature of these electronic states and the behavior of a (1/3 1/2) LEED spot upon oxygen contents in the facets indicate that the formation is a heterogeneous mixture of the clean Si(1 1 3) facets free of oxygens and other facets containing oxygen atoms.