Structure and oxidation kinetics of the Si(100)-SiO2 interface

TL;DR

This study uses first-principles calculations to analyze the structure, electronic properties, and oxidation kinetics of the Si(100)-SiO2 interface, revealing a transition region with sub-oxide species and proposing a mechanism for oxygen diffusion.

Contribution

The paper introduces a combined Monte-Carlo and first-principles approach to characterize the Si(100)-SiO2 interface and investigates oxygen behavior, providing new insights into oxidation mechanisms.

Findings

Identification of a ~20Å transition region with sub-oxide species

Peroxyl linkage is energetically favored for atomic oxygen in SiO2

Proposed mechanism for oxygen diffusion relevant to oxidation processes

Abstract

We present first-principles calculations of the structural and electronic properties of Si(001)-SiO2 interfaces. We first arrive at reasonable structures for the c-Si/a-SiO2 interface via a Monte-Carlo simulated annealing applied to an empirical interatomic potential, and then relax these structures using first-principles calculations within the framework of density-functional theory. We find a transition region at the interface, having a thickness on the order of 20\AA, in which there is some oxygen deficiency and a corresponding presence of sub-oxide Si species (mostly Si^+2 and Si^+3). Distributions of bond lengths and bond angles, and the nature of the electronic states at the interface, are investigated and discussed. The behavior of atomic oxygen in a-SiO2 is also investigated. The peroxyl linkage configuration is found to be lower in energy than interstitial or threefold configurations. Based on these results, we suggest a possible mechanism for oxygen diffusion in a-SiO2 that may be relevant to the oxidation process.