This work measures the C and O K-edge x-ray absorption near-edge structure (XANES) spectra of hydrogenated amorphous carbon (a-C:H) films deposited at various baking temperatures Tb (Tb = 300–500 °C at 50 °C). The C–H σ* peak related to the content of the sp2 graphite-like bonding in the C K-edge spectra was found to yield to the C–H π* peak related to the sp3 diamond-like bonding at high temperature (500 °C). We find that the intensities of both the sp2 and sp3 features in the C K-edge XANES spectra decrease with increase of Tb, which suggests an increase of the defect concentration with Tb. The intensities of the O K-edge XANES spectra are found to decrease with increase of Tb, which suggests thermally induced decomposition of carbonyl contaminants on the surface. The elemental analysis C/O (or O/C) ratio was obtained from XPS spectra and indicates that films are not hydrogenated amorphous carbon but rather oxyhydrogenated amorphous carbon thin films.
Journal of Physics Condensed Matter 16(32), pp.5713-5719