Increase of sp3 content in a-C films with gas cluster ion beam bombardments; XPS and NEXAFS study

Abstract

Gas cluster ion beams (GCIB) were used for surface modification of amorphous carbon (a-C) or tetrahedral carbon (ta-C) films, and in-vacuum XPS and near edge X-ray absorption fine structure (NEXAFS) measurements were carried out for evaluation of sp2/sp3 ratio. Since GCIB deposit its kinetic energy at local area, it leads to formation of high energy density state on surface. From XPS analysis, it was shown that sp3 contents in carbon films increased with increasing acceleration voltage (Va) and it showed highest value at Va of 10 kV. NEXAFS measurements also showed decrease of sp2 content at Va of 10 kV. GCIB irradiations can assist to form sp3 rich layer on amorphous carbon surface.