EELS analysis of hydrogenated diamond-like carbon films

Electron energy-loss spectroscopy (EELS) has been used to analyze the structure of hydrogenated diamond-like carbon (DLC) films deposited by plasma-assisted CVD (PACVD) under a variety of conditions. Spectra obtained from highly oriented pyrolytic graphite and amorphous carbon were used as references. The ratio sp(3) (tetragonal) to sp(2) (trigonal) carbon sites in the DLC films was quantified for different hydrogen contents from the near-edge structure (ELNES) of the carbon K-edge and compared with a constrained network structure model. The results were in agreement with this model and showed an increase of the ratio sp(3) to sp(2) with increasing hydrogen content in the material. The irradiation damage caused by the electron beam increased the sp(2) fraction even when using a N-2-cooled specimen holder. In order to better identify the chemical bonding from the carbon K near-edge structure, the first two peaks of the edge were deconvoluted to obtain the peaks of individual transitions, after subtracting the simulation of the carbon K-edge continuum to extract the core-excitation peaks. The relative contributions of ls/pi *(C=C), ls/sigma *(C-H) and ls/sigma *(C-C) were thus obtained. The position in energy of each peak is discussed. (C) 1998 Published by Elsevier Science S.A.