Thermal stability of plasma deposited thin films of hydrogenated carbon-nitrogen alloys

The need to grow high quality semiconducting hydrogenated amorphous carbon (a-C:H) thin films to allow n-type electronic doping by nitrogenation has l ead us to deposit films with low paramagnetic defect density (10(17) cm(-3) ). The films were grown on the earthed electrode of a radio frequency drive n plasma enhanced chemical vapor deposition system using methane, helium an d a range of nitrogen concentrations as the precursor gases. The deposited films are shown to be polymer like. Changes in the chemical structure and r elative bond fractions as a function of the nitrogen flow rate into the pla sma chamber and ex situ annealing are reported. Particular attention is pai d to changes in the film structure after annealing at 100 degrees C, since an increase in the E-04 optical band gap is observed as a function of nitro gen flow after the anneal. This suggests a decrease in the defect density o f the film. (C) 1999 American Institute of Physics. [S0021-8979(99)08622-3] .