XPS and EPMA study of CVD diamond, hydrogenated amorphous carbon and graphite films

We applied X-ray photoelectron spectroscopy (XPS) to investigate commercially available polycrystalline CVD diamond, hydrogenated amorphous carbon (a-C:H) and graphite films. The measurements we carried out on three samples exposed for a long time to air and having therefore contaminated surfaces, were made with the use of a conventional non-monochromatic X-ray source. In particular, we analyzed the carbon C Is and O Is core lines - including their loss features - and the valence band spectra. A direct comparison of these spectral features of the three samples clearly demonstrated the capacity of the XPS technique to discriminate between various carbon phases. The CVD diamond spectrum proved to be the superposition of two spectra : one of which results from the nearly uncontaminated diamond surface and the other from heavily contaminated regions, very likely localized at grain boundaries, as confirmed by electron probe microanalysis (EPMA).