Optical band gap of nitrogenated amorphous carbon thin films synthesized by microwave surface wave plasma CVD

Nitrogenated amorphous carbon (a-C:N) thin films were prepared on silicon and quartz Substrates by microwave surface wave plasma chemical vapor deposition system, aiming to control optical band gap (E,) of the films for photovoltaic solar cells application. For films deposition, we used argon as carrier gas, nitrogen as dopant and hydrocarbon source gases, such as camphor dissolved with ethyl alcohol (3:7) and acetylene. The E, of the films has been decreased from 4.1 to 2.4 eV and 2.2 to 1.6 eV with alcohol plus camphor and acetylene source gases respectively by nitrogen doping. The E-g of the a-C:N films can be tuned from 2.4 to 0.95 eV by thermal annealing treatment. These results show that it is possible to control the E, by nitrogen doping with different carbon source gases and by post growth annealing of the films. (c) 2008 Elsevier B.V. All rights reserved.