Abstract :
The analysis of the X-ray photoelectron spectra (XPS) of the C 1s core level of pulsed laser deposited diamond-like carbon thin films, obtained at different laser intensities is presented. These spectra are deconvoluted into two different contributions, at 284.4 eV and 285.2 eV, which are respectively attributed to sp2 and sp3 hybridized carbon atoms. From the deconvoluted spectra, the sp3 content in the films is evaluated. It is found to increase from 33% to about 60% as laser intensity is varied from 0.9×108 to 7.1×108 W/cm2. These measurements have been compared to those obtained by the analysis of the C KLL X-ray excited Auger electron spectra. The two methods provide the same qualitative variation of the sp3 content with laser intensity. However, the XPS of the C 1s core level yields systematically higher sp3 content values. These differences are attributed to the presence of an sp2 rich outer layer on the surface of the DLC films, as confirmed by angle-resolved XPS. The analysis of the C 1s peak is shown to be a very simple and direct method to evaluate the sp3 content in unhydrogenated DLC thin films.
