Defect density and atomic bond structure of tetrahedral amorphous carbon (ta-C) films prepared by filtered vacuum arc process

Abstract

Defect density of tetrahedral amorphous carbon (ta-C) film prepared by filtered vacuum arc process was investigated in a wide range of fraction of sp3 hybridized bond. We could observe a close relationship between unpaired spin density measured by electron spin resonance spectroscopy and their atomic bond structure: the defect density was proportional to the content of sp3 hybridized bond in the film. Near edge x-ray absorption fine structure analysis further showed that the content of the surface C–H bonds presumably due to the absorption of hydrocarbon to the surface dangling bond also increased with increasing content of sp3 hybridized bond. The observed dependence was discussed in terms of the degree of clustering or pairing of the isolated sp2 sites.