NITROGEN DOPING OF TETRAHEDRAL AMORPHOUS-CARBON

N has been found to be an effective n-type dopant of tetrahedral amorphous carbon, ta-C. Molecular orbital diagrams and band calculations are used to describe the electronic structure of various C-N bonding configurations and account for the doping mechanism. The doping configuration of N at low concentrations is the substitutional, sp(3) coordination. The doping efficiency is estimated to be about 1%. Two possible non-doping configurations of N, the trivalent and the compensated are both consistent with the electron energy loss spectra. Both N and C adopt graphitic bonding a high N concentrations.