Role of lone-pair interactions and local disorder in determining the interdependency of optical constants of a-CN:H thin films -: art. no. 195415

In this paper the role of the nitrogen bonding regime and of the presence of lone-pair electrons due to nitrogen atoms on the optical properties of disordered hydrogenated carbon nitride (a-CN:H) thin films grown by reactive sputtering are studied. Evidence is given for the existence of a variable amount of mixing between nitrogen atom lone-pair states and pi bonding electronic states in different samples. It is proved that such mixing favors the stabilization of lone pairs. By properly analyzing the role of the local disorder and of the lone-pair pi mixing, an ellipsometric model able to describe the optical complex dielectric constant, measured in the UV-visible range, is developed. The existence of an optical scaling law for the real and imaginary parts of the dielectric function is demonstrated.