X-ray absorption of nitrogen-doped amorphous carbon films for determining sp2/sp3 bonding concentrations

A method of analyzing X-ray absorption spectra of nitrogen-doped amorphous carbon (a-C) samples was developed to determine their sp2 bonding concentrations. The films under consideration are simultaneously deposited onto polytetrafluoroethylene (PTFE) polymer or silicon wafer substrates by hot wire plasma sputtering of graphite. sp2 bonding concentrations of a-C films deposited on PTFE increase from 74% to 93% with growing nitrogen doping. Silicon substrate films yield the same general trend, but show that the near surface electronic structure of a-C films depends on the substrate.