Conduction processes in boron- and nitrogen-doped diamond-like carbon films prepared by mass-separated ion beam deposition

Abstract

Boron- and nitrogen-doped diamond-like amorphous carbon (DLC) films were prepared by alternating direct deposition of low energy mass-separated 12C+ and dopant ions. Concentration vs. depth profiles for N and B dopants were determined by neutron depth profiling. The measured current-voltage characteristics of these films, which were deposited on polished stainless steel, are explained best by Frenkel-Poole emission for high electric fields. Two different trap states Φ1 and Φ2 were found to contribute to the conduction process. At low electric fields our results suggest that conduction is due to variable-range hopping via localized states at the Fermi level. The doped DLC films show a higher electrical conductivity, indicative of an increased density of localized states, rather than a shift in the Fermi level. A diode-like device was prepared, but the measured I-V curves did not indicate that a p-n junction had formed. DLC/Si heterojunctions were also prepared and their current-voltage characteristics are presented and discussed.