title: Origin of O 1s core-level shifts on oxygen adsorbed Si(111)-(7x7)
abstract: Density functional calculations are used to examine the chemical and structural origin of O 1s core-level shifts measured on the initial oxidation stage of Si(111)-(7x7). Our analysis of metastable core-level peaks leads to a conclusive identification of the long-sought metastable oxidation species as a tetrahedral SiO4 unit, formed by two successive O2 adsorptions on a Si adatom. The origin of a higher-binding core-level shoulder is clarified by the presence of a threefold-coordinated subsurface O atom, introduced as a decay product of the metastable SiO4 unit. The present study provides a detailed atomic-scale picture of the initial oxidation process of Si(111)-(7x7).
authors.affiliation: Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.initials: SH
authors.lastname: Lee
authors.initials: MH
authors.lastname: Kang