Successive oxidation stages and annealing behavior of the Si(111) 7×7 surface observed with scanning tunneling microscopy and scanning tunneling spectroscopy

Abstract

Scanning tunneling microscopy and spectroscopy reveal at least a two‐stage reaction process which occurs at adatom sites on Si (111) 7×7 surfaces exposed to oxygen at 300 K. Reacted adatoms in the first stage have a slightly modified electronic spectrum and show a preference for the faulted half and the corners of the 7×7 unit cell, while second stage adatoms appear similar to ‘‘missing’’ or ‘‘lowered’’ adatoms in topographic images. Annealing the surface to ∼625 K causes large changes in the number and site preference of the two stages.