Effects of annealing ambient on the photoluminescence properties of Si-rich oxide/SiO2 multilayer films containing Si-nanocrystals

In this study, Si-nanocrystals (Si-NCs) have been prepared by annealing Si-rich oxide (SRO)/SiO2 multilayer films in Ar and N2, and the effects of annealing ambient on the photoluminescence (PL) properties are studied. XPS results show that the chemical compositions for the SRO and SiO2 layers are SiO1.1 and SiO2, respectively. FTIR results show that phase separation between Si and SiO2 occurs after annealing treatment, and Si-NCs are obtained which have been proved by the TEM images. Large and high density Si-NCs are obtained in the Ar-annealed film, and high structural disorder exists at the interface of Si-NCs. Compared with the film annealed in N2, a 2.4 times PL enhancement is obtained for the Ar-annealed sample, and the PL peak shifts toward low energy. Two lifetime distribution bands are obtained by fitting the time-resolved PL spectra, and the proportion of slow PL decay component increases from 69.7 to 84.0 %. The PL intensity for the Ar-annealed film is further enhanced by hydrogen passivation, and the slow PL decay component is increased to 87.5 %. Analyses show that both interface states recombination and quantum confinement effect (QCE) related optical transition in the Si-NCs exist in the optical emission process, and intense PL can be obtained only when the QCE become dominant PL mechanism.