Photoluminescence of silicon carbonitride thin films: The interdependence of post-deposition annealing and growth temperature

Silicon carbonitride (SiCN) thin films have recently emerged as the promising class of multifunctional materials because of their unique properties inherited from binary submatrices of silicon carbide, silicon nitride, and carbonitride. The luminescence mechanism of such ternary materials is complex and is influenced by slight changes in the film composition, deposition temperature, and post-deposition annealing temperature. This paper reports the temperature dependence of luminescent centres in SiCN thin films grown using the electron cyclotron plasma enhanced chemical vapour deposition (ECR PECVD) at different deposition temperatures, which are subsequently subjected to a wide range of annealing temperatures. With the increase of the deposition temperature, the photoluminescence (PL) sub-band positioned at around 1.8 eV (650 nm) intensifies. Following the annealing, the changes of the PL spectra at higher annealing temperatures are dominated by the emission related to this PL sub-band. The white luminescence of SiCN thin films observed under excitation by a 325 nm laser is explained in terms of the radiative defects at localized carbide- and nitride-related states. We assign the changes of the intensity and shape of the PL-sub bands mainly to the evolution of carbon-related defects. The observed variation of the PL emission of different samples was linked with the film restructuring and original growth temperature. We discuss how the post-deposition thermal annealing influences the emissions associated with the carbon and nitride states differently in the samples grown at different deposition temperatures, which have different compositions.