Initial Backbond Oxidation at an Unpaired Dangling Bond Site on a Hydrogen-Terminated Si(100)2×1 Surface

The oxidation reaction at an unpaired dangling bond (DB) site on a hydrogen-terminated Si(100)2×1 surface was studied using an ultrahigh-vacuum scanning tunneling microscope. The surface image was observed in situ during the exposure to O 2 molecules at room temperature. During exposure, the unpaired DBs induced structural changes around themselves, and they were mostly localized on one side of a Si dimer bond. We conclude that the backbonds near an unpaired DB were preferentially oxidized, following the dissociation of O 2 molecules at the unpaired DB site. Based on high-resolution measurements, models of backbond-oxidized-structure were proposed.