Referencing the XPS Binding Energies on Oxidized Surfaces of SiC
摘要
This study addresses one major uncertainty concerning referencing the XPS binding energies (BEs) on oxidized surfaces of silicon carbide (SiC). Based on the extensive catalogue of SiC powder spectra, two spectral features are compared as potential BE references, namely, the C1s photopeak from adventitious carbon and the O1s photopeak from the native oxidized overlayer. Referencing to adventitious carbon produces a systematic shift in the BEs of all species depending upon the degree of surface oxidation. In contrast, referencing to O1s yields SiC BEs that are reproducible to ±0.2 eV across a wide range of SiO2 surface concentrations. Stability in referencing to O1s is attributed to the prominent Si‒O‒Si coordination of oxygen over a wide range of SiCxOy surface compositions. When referenced to O1s, the BE values reported for different types of oxidized SiC substrates (crystal faces, films) compare favorably with those of the powders. Using the O1s reference and a few constraints to stabilize the curve fitting of the Si2p and C1s spectral envelopes, a broad range of SiC powder surface chemistries can be described in a consistent manner and in line with knowledge on other types of SiC substrates.