Optical characterisation of CNx thin films deposited by reactive pulsed laser ablation

Abstract

Optical absorption measurements on CNx thin films produced by reactive pulsed laser ablation (RPLA) at different pressures of nitrogen in the growth chamber were performed. The influence of growth regime on optical properties (n,k) of the CNx films has been examined with IR and UV-VIS spectroscopy. The dependence of the absorption coefficient α on the photon energy ℏω at the edge of the absorption band is well described by the relation αℏω=B(ℏω−Eopt)2 indicating the presence of allowed indirect transitions in the 0.8–3.0 eV photon energy range. Furthermore, we observed a decrease in the optical gap values with increasing N concentration in the deposited films. Fourier transform infrared (FTIR) spectra were also employed to analyse the chemical bonding state between the different species present in the films.