Temperature-dependent carrier recombination processes in nanocrystalline Si/SiO₂ multilayers studied by continuous-wave and time-resolved photoluminescence

50-period SiO₂/SiO_x layers have been prepared on Si wafers by ion beam sputtering deposition and subsequently annealed to form Si nanocrystals (NCs) in the SiO_x layer. The integrated photoluminescence (PL) intensity of the samples with x ≤ 1.6 increases on decreasing the temperature down to a certain temperature named as T_C, but below T_C, it decreases. T_C is maintained at 95 K, almost irrespective of x. The rate of decrease of the PL below T_C gets slower as x increases up to 1.6, and at x ≤ 1.8, the PL intensity shows a monotonic increase with decreasing temperature. This phenomenon is strongly related to the change in the temperature dependence of the PL decay rate at around T_C as x varies. These results can be explained by the fact that the PL behaviours are increasingly influenced by the NCs' environment such as the defect states of the Si NCs/SiO₂ interfaces as x increases.