Qualitative analysis of a diamondlike carbon film by angle-resolved x-ray photoelectron spectroscopy

Abstract

Angle-resolved x-ray photoelectron spectroscopy was used to investigate the surface of a diamondlike carbon film prepared by the ionized deposition method. We then analyzed the C 1s spectra using the Doniach-Šunjić (DŠ) [J. Phys. C 3, 285 (1970)] function convoluted with a Gaussian function. Consequently, we obtained four fitting curves for the carbon components in each spectrum, regardless of the assumption of the singularity index (α) in the DŠ function, which expresses the asymmetry of the C 1s spectrum. The curves were assigned in the order of binding energy to bulk sp3 carbon (283.7–283.8eV), bulk sp2 carbon (284.2–284.3eV), surface sp2 carbon (284.7–284.8eV), and surface sp3 (285.3–285.4eV) carbon. We further considered the influence of the assumption of α. Consequently, we suggest that the C 1s spectra can be quantitatively analyzed without considering the influences of α when the ratio of α for sp2 carbon to that for sp3 carbon [α(sp2):α(sp3)] is between 10:0 and 5:5. The distribution in the α ratio may indicate that the sp2 and the sp3 carbon atoms can interact with each other (hybridization) and differ from those highly oriented pyrolytic graphite and diamond, respectively.