Optical and structural properties of amorphous carbon thin films deposited by microwave surface-wave plasma CVD

Nitrogen doped amorphous carbon (a-C : N) thin films were deposited on silicon and quartz substrates by microwave surface-wave plasma chemical vapor deposition technique at low temperature (< 100 °C). We used argon (Ar), camphor dissolved in alcohol and nitrogen (N) as carrier, source and dopant gases, respectively. Optical band gap (Eg) decreased from 4.1 to 2.4 eV when the N gas concentration increased from 0 to 4.5%. The films were annealed at different temperatures ranging from 150 to 450 °C in Ar gas environment to investigate the optical and electrical properties of the films before and after annealing. Both Eg and electrical resistivity (ρ) decreased dramatically to 0.95 eV and 5.7 × 104 (Ω-cm) at 450 °C annealing. The structural modifications of the films leading to more graphite as a function of the annealing temperature was confirmed by the characterization of Raman spectra.