MOLECULARLY ADSORBED OXYGEN SPECIES ON SI(111)-(7X7) - STM-INDUCED DISSOCIATIVE ATTACHMENT STUDIES

Scanning tunneling microscope (STM)-induced selective bond breaking in individual molecules and conventional STM imaging are combined to det ermine the nature of chemisorbed O-2 species formed during the initial stages of silicon (111)-(7x7) oxidation. A selective atomic-scale mod ification mechanism that involves dissociative electron attachment of tip-emitted electrons to empty adsorbate orbitals is introduced. Two m olecular species were found: one involves O-2 bonded to an already oxi dized silicon adatom, and the other involves an O-2 molecule that is b onded to a second-layer rest atom and interacting with two silicon ada toms.