SURFACE-ANALYSIS OF CVD CARBON USING NEXAFS, XPS AND TEM

Chemical and morphological characterization of carbon thin films produ ced by chemical vapor deposition (CVD) of hydrocarbon gases onto a har d carbon substrate has been performed using various surface analytical techniques. Semiquantitative analyses of the surface concentration of C=C double bonds have been conducted using near edge X-ray absorption fine structure (NEXAFS) at the C K edge and core level X-ray photoele ctron spectroscopy (XPS). NEXAFS spectra of CVD carbon films are simil ar to those of well-ordered graphite. Rather surprisingly, however, it has been revealed that the CVD carbon films contain less C=C double b onds than that of the hard carbon. Intensities of pi-pi shake-up sate llite of the C Is XPS peak have been measured, and the results were co nsistent with those of NEXAFS. Smaller concentrations of C=C double bo nds can be attributed to the incomplete dehydrogenation due to the rel atively low temperature of the CVD treatment. High resolution transmis sion electron microscope (TEM) images of CVD carbon showed preferentia l orientation of graphite-like plane units in the direction parallel t o the surface, suggesting the formation of large molecules in gas phas e reaction prior to deposition. (C) 1998 Elsevier Science B.V.