The effects of CeF_3 doping on the photoluminescence of Si nanocrystals embedded in a SiO_2 matrix

摘要

The effects of CeF_3 doping on the photoluminescence (PL) of Si nanocrystals embedded in a SiO_2 matrix, assigned as nc-Si:SiO_2, have been studied. The nc-Si:SiO_2 sample was prepared by means of reactive evaporation followed by thermal annealing, and CeF_3 doping was conducted via thermal diffusion. It is found that the doping of CeF_3 is able to enhance the PL intensity of nc-Si by a factor as large as 3.7. With the increasing doping concentration, the degree of PL intensity enhancement increases until a maximum is reached, and then it drops down. This trend also holds for the PL intensity enhancement versus the diffusion annealing temperature. A continuous redshift of the PL peak was observed with the increasing doping concentration and diffusion annealing temperature. Beyond a certain concentration or temperature, the PL peak starts to shift back towards shorter wavelengths. The doping effects on the PL intensity were explained by a model of electron transfer from Ce ions to nc-Si, while the trends of PL peak shift were accounted for with the help of a previous model referring to the size distribution of nc-Si crystallites versus nc-Si:SiO_2 film thickness (Fang et al 2004 Nanotechnology 15 494); the peak shift was also related to the chemical reaction between Ce and Si.