A novel approach for oxide scale growth characterization: Combining etching with atomic force microscopy

Abstract

The combination of atomic force microscopy (AFM) analysis of oxide scales before and after chemical etching is presented as a fast, powerful method to gain information on oxide scale growth kinetics. While not limited to the field of ceramics, we chose the thermal oxidation of silicon carbide at high temperatures (1,400°C) as an example for the potential of the AFM/etching method. SiC is a promising semiconductor material with many high-temperature applications during which not only simple oxidation, but also crystallization of the initially vitreous silica scale occurs. We demonstrate how AFM/etching analysis of crystalline areas (radialites) yields valuable information on the growth rate of the crystalline and amorphous silica scale. This can be directly translated into a statement on the oxidation passivation potential of a certain oxide scale state/morphology with important consequences for the actual high-temperature application. Also, the influence of impurities is addressed as this is an essential aspect for real-world application of silicon carbide (both, as a refractory and ceramic material).