Photoluminescence of granular CdSe films

We have produced granular films with a high density of CdSe clusters by a deposition method using a cluster beam. The photoluminescence spectra of those granular films were measured over the temperature range of 80–300 K in order to explore quantum size effects and interactions between clusters. The results were compared with photoluminescence of a thin film which was made by a conventional vacuum evaporation method. It has been found that the observed blue-shifted broad photoluminescence band of the granular film cannot be explained simply by the calculation using the effective mass approximation derived by Kayanuma with taking into account the size distribution of CdSe clusters in the film. The discrepancy suggests that the luminescence yield may depend strongly on the cluster size. The surface states and connectivity of clusters which may influence the interaction between clusters in such a granular film should be also considered as well as the size-dependent luminescence yield to explain the temperature dependence of peak energy of the photoluminescence.