Structure and optical property of the a-C:N films synthesized by filtered cathode vacuum arc

Amorphous carbon nitride (a-C:N) films were deposited on silicon using a 90°-bend filtered cathode vacuum arc system. The optical properties of a-C:N films were studied using spectroscopic ellipsometry and cathodoluminescence. The results are discussed in view of the electronic structure of diamond, graphite and the density of states of the a-C:N films. It is demonstrated that the investigation of the a-C:N films reveal not only their diamond- or graphite-like character, but also their local electronic structure and configuration, based on the fact that the Nπ+π→Nπ*+π* in sp2 sites and Nσ→Nσ* in sp3 sites take place in carbon and nitrogen atoms. Nitrogen in sp3 sites of the a-C:N films causes the blue emission. The energies of Nπ+π→Nπ*+π* in sp2 sites and Nσ→Nσ* in sp3 sites are about 1.91 and 2.67 eV, respectively, in a-C:N films.