Evolution of the opto-electronic properties of amorphous carbon films as a function of nitrogen incorporation

The present work provides correlations between the optical, electronical and microstructural properties of amorphous carbon nitride films (a-CNx) deposited by Direct Current (DC) magnetron sputtering technique versus the N2/Ar + N2 ratio. The microstructure of the films was characterized by Raman spectroscopy and optical transmission measurements. The evolution of both the density of states (DOS) located between the bandtail states and the density of states around the Fermi level N(Ef), have been investigated by electrical measurements versus temperature varying the N2/Ar + N2 ratio. The evolution of the microstructure versus N reveals a continuous structural ordering of the sp2 phase, which is confirmed by the optical and the conductivity measurements. The conductivity variation was interpreted within the framework of the band structure model of the π electrons in a disordered carbon with the presence of localized states.