Oxidation kinetics of single crystal silicon carbide using electron microscopy

Abstract

The thickness of the specific oxide phase scale formed on single crystal silicon carbide was measured to determine the activation energy on both the Si-face and the C-face. The oxide scales were thermally formed on both the Si- and the C-face of 6H-SiC at 1273-1473 K in a pure oxygen environment. Microstructures of the oxide scales were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Crystalline oxide scales were found to be randomly distributed on the surfaces of both the Si-face and the C-face of the oxidized samples. The focused ion beam (FIB) micro-sampling technique was employed to prepare the specific site specimens for thickness measurement of the oxide scales in the regions where the oxide scales were composed of only uniform amorphous silica. The thickness of the oxide scales was measured directly to high accuracy using SEM and TEM, and fitted to the Deal-Grove model. The oxidation activation energy for the parabolic rate constant was found to be 358 kJ/mol for the Si-face and 85 kJ/mol for the C-face. The low activation energy for the C-face that is close to that for oxygen diffusion in silica strongly suggested that the rate controlling process of the C-face oxidation is the diffusion of oxygen in the oxide layer. (C) 2012 The Ceramic Society of Japan. All rights reserved.