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The amorphous carbon thin films have been deposited on silicon and quartz substrates by microwave surface wave plasma chemical vapor deposition at low temperature (<100°C) in Ar∕CH4 phase gas. Doping of iodine has been done in the postdeposited films by exposing them in iodine vapor. The photovoltaic measurements of the films were carried out before and after iodine doping. The results show dramatic decrease of optical gap from 3.4 to 0.9 eV corresponding to nondoping to iodine doping conditions, respectively. The preliminary photovoltaic characteristics of the film deposited on n-type silicon substrate under light illumination (AM1.5, 100mW∕cm2) reveal a short-circuit current density of 1.15μA∕cm2, open-circuit voltage of 177 mV and fill factor of 21.7%.

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The effects of annealing temperature on the optical properties of nitrogenated amorphous carbon (a-C:N) films grown on quartz substrates by a novel surface wave microwave plasma chemical vapor deposition (SWMP-CVD) method are reported. The thickness, optical, structural and bonding properties of the as-grown and anneal-treated a-C:N films were measured and compared. The film thickness decreased rapidly with increasing annealing temperature above 350°C. A wide range of optical absorption characteristics is observed, depending on the annealing temperature. The optical band gap of as-grown a-C:N films is approximately 2.8 eV, gradually decreasing to 2.5 eV for the films anneal-treated at 300°C, and beyond that decreasing rapidly down to 0.9 eV at 500°C. The Raman and FTIR spectroscopy measurements have shown that the structural and composition of the films can be tuned by optimizing the annealing temperature. The change of optical, structural and bonding properties of SWMP-CVD-grown a-C:N films with higher annealing temperature was attributed to the fundamental changes in the bonding and band structures of the films.

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