Ab initio study of reflectance anisotropy spectra of a sub-monolayer oxidized Si(100) surface

TL;DR

This study uses ab initio DFT calculations to analyze how oxygen adsorption affects the reflectance anisotropy spectra of Si(100) surfaces during early oxidation stages, revealing preserved features and new spectral structures.

Contribution

It provides the first detailed ab initio analysis of RAS changes during sub-monolayer oxidation of Si(100), linking electronic transitions to spectral features.

Findings

Dangling bonds and main RAS features are preserved after 50% oxidation

A small red shift of the first peak occurs with oxidation

A new spectral structure appears at about 1.5 eV

Abstract

The effects of oxygen adsorption on the reflectance anisotropy spectrum (RAS) of reconstructed Si(100):O surfaces at sub-monolayer coverage (first stages of oxidation) have been studied by an ab initio DFT-LDA scheme within a plane-wave, norm-conserving pseudopotential approach. Dangling bonds and the main features of the characteristic RAS of the clean Si(100) surface are mostly preserved after oxidation of 50% of the surface dimers, with some visible changes: a small red shift of the first peak, and the appearance of a distinct spectral structure at about 1.5 eV. The electronic transitions involved in the latter have been analyzed through state-by-state and layer-by-layer decompositions of the RAS. We suggest that new interplay between present theoretical results and reflectance anisotropy spectroscopy experiments could lead to further clarification of structural and kinetic details of the Si(100) oxidation process in the sub-monolayer range.