Surface analysis of carbon-hydrogen bonds in diamondlike carbon films by X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) was used to analyze the carbon-hydrogen bonds near the surfaces of two types of diamondlike carbon (DLC) film with different hydrogen distribution, which were prepared by the unbalanced magnetron sputtering (UBMS) and ionized deposition (ID) methods, respectively. Elastic recoil detection (ERD) analysis revealed that, in the UBMS films, hydrogen is distributed homogeneously along the depth axis, while in the ID film it is distributed inhomogeneously and concentrated at the surface. The C 1s spectra of the UBMS films with different hydrogen concentrations suggested that the spectra are decomposed into four components, corresponding to the carbon-hydrogen and carbon-carbon bonds of the sp² and sp³ carbons. A correlation between the hydrogen concentrations obtained by the XPS and ERD analyses was observed. The C 1s spectrum of the ID film depended on the emission angle, suggesting that the carbon-hydrogen bonds concentrate at the surface. This result agreed with the ERD result. Both correlations suggested that XPS can analyze hydrogen as an atom bound to a carbon atom and be a comprehensive surface analytical tool for DLC films.