Characterization of hydrogenated amorphous carbon films produced by plasma-enhanced chemical vapour deposition with various chemical hybridizations

Thin films (similar to 100 nm) of hydrogenated amorphous carbon (a-C:H) hav e been prepared by plasma-enhanced chemical vapour deposition (PECVD). Surf ace analysis techniques such as elastic recoil detection with an electromag netic filter (ERD ExB), X-ray photoelectron spectroscopy (XPS) and Auger el ectron spectroscopy (AES) have been used to measure the influence of the ar rangement of the internal structure on the retention of hydrogen and the de sorption of methane and ethylene from the PECVD carbon films under thermal and ion beam treatments. The parameters of deposition have been adjusted in such a way that the chemical hybridization of the carbon atoms could be ta ilored (mainly sp(2), sp(3) or a mix of the two hybridizations). The therma l desorption behaviour appears to be greatly influenced by the sp(3)/sp(2) hybridization ratio of the carbon films. With increasing ratio, desorption of hydrogen is shifted to higher temperatures, ethylene desorption is decre ased and methane desorption is increased. Ion beam induced desorption (IBID ) also depends on the hybridization ratio of the carbon deposits. IBID and TDS results can be understood in terms of enhanced hydrogen mobility for lo wer density (lower sp(3)/sp(2) ratio) films accompanied by hydrogen recaptu re in films with a significant degree of sp(2) hybridization. (C) 1999 Publ ished by Elsevier Science S.A. All rights reserved.