Abstract
Amorphous hydrogenated carbon films show a characteristic photoluminescence behavior that is of great interest for the study of their electronic structure. In the present paper we develop a model of the photoluminescence process in a polymerlike hydrocarbon on the basis of a mixed hybridization of the carbon atoms in this material. The phase is assumed to be confined in clusters embedded within a matrix. We assume excitation and recombination to take place within a single cluster. Thus the overall photoluminescence signal consists of the contribution of all single clusters, having different energy-gap values , due to their various sizes and/or shapes. Applying the model to experimental data, we deduce a material-characteristic function f() that turns out to be representative of the distribution of the different energy-gap values of the clusters in the film. The good agreement with experimental data suggests that the classical Tauc gap in a-C:H films is a value averaging over all single-cluster gap values . Moreover, our model reproduces all the peculiar features of the photoluminescence behavior of a-C:H films, such as the nonactivated dependence upon temperature.
- Received 27 July 1994
DOI:https://doi.org/10.1103/PhysRevB.51.2143
©1995 American Physical Society