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O: Oberflächenphysik

O 39: Adsorption an Oberflächen (V)

O 39.1: Talk

Friday, March 31, 2000, 11:15–11:30, H44

Identification of the Initial-Stage Oxidation Products on Si(111)-(7×7) — •Sung-Hoon Lee and Myung-Ho Kang — Pohang University of Science and Technology, Pohang 790-784, Korea

Chemisorption of oxygen molecules on Si(111)-(7×7) has been studied extensively as a model for the initial-stage silicon oxidation. The basic step to the surface oxidation is the dissociation of the adsorbed O₂ molecules, but the dissociation procedure and the atomic structure of the reaction products are still a subject of investigation. We present here the result of density-functional theory calculations for this system: The equilibrium structures of all possible surface oxidation configurations on the most reactive Si adatom site have been determined. Our electronic and vibrational analysis clarifies the atomic origin of the oxygen-induced UPS and EELS features. Moreover, the calculated decay pathways of the metastable structures and the comparison of the calculated O 1s core-level shifts with XPS data make it possible to identify unambiguously the experimental metastable and stable structures, thereby providing a convincing atomic-scale picture of the initial-stage oxidation process of Si(111)-(7×7).