Semiconducting hydrogenated carbon-nitrogen alloys with low defect densities

Abstract

Low paramagnetic defect density hydrogenated amorphous carbon (a-C:H) films grown by radio frequency driven plasma enhanced chemical vapour deposition (rf-PECVD) system are characterized using ultraviolet/visible spectroscopy and Rutherford backscattering spectroscopy (RBS). The changes in the optical band gap, Urbach tail width, and Tauc B-1 parameter as a function of nitrogen flow rate and ex situ annealing from 100 to 400 °C for 300 s are examined. Particular attention is paid to changes in the film structure after annealing at 100 °C, since an increase in the E04 optical band gap is observed as a function of nitrogen flow. This increase is shown to be a result of the restructuring of the chemical bonds present, despite there being no change in the refractive index of the films, which suggests a decrease in the defect band tails of the films.