Competing Atomic and Molecular Mechanisms of Thermal Oxidation

TL;DR

This paper investigates the oxidation mechanisms of SiC and Si, revealing atomic and molecular oxygen as key oxidants and how interface properties influence these processes, using first-principles calculations.

Contribution

It identifies the specific oxidants for SiC faces and compares oxidation mechanisms between SiC and Si, highlighting the role of interfaces in controlling these mechanisms.

Findings

Atomic oxygen is the oxidant for Si-face SiC.

Molecular oxygen is the oxidant for C-face SiC.

Interface properties influence the competition between atomic and molecular oxidation mechanisms.

Abstract

The oxidation of SiC and Si provide a unique opportunity for studying oxidation mechanisms because the product is the same, SiO2. Silicon oxidation follows a linear-parabolic law, with molecular oxygen identified as the oxidant. SiC oxidation obeys the same linear-parabolic law but has different rates and activation energies and exhibits much stronger face-dependence. Using results from first-principles calculations, we show that atomic and molecular oxygen are the oxidant for Si- and C-face SiC respectively. Comparing SiC with Si, we elucidate how the interface controls the competition between atomic and molecular mechanisms.