Influence of the annealing temperature on the photoluminescence of Er-doped SiO thin films

Abstract

Er-doped amorphous silicon suboxide thin films were prepared by the coevaporation method. The Er concentration was varied from 0.4to6at.% and the samples were annealed at different temperatures up to 900°C. The samples exhibit a broad photoluminescence band in the visible range. Both energy and intensity of this band were dependent on the annealing temperature. For as-deposited films and samples annealed below 500°C, this band was assigned to defects in the oxide films. For higher annealing temperatures, this photoluminescence band shifted to higher wavelengths and was correlated to the appearance of amorphous silicon clusters. Two narrow bands in the near-infrared range at 0.98 and 1.54μm were also observed for the annealed samples. The intensity of these Er-related luminescence was maximal for an annealing temperature equal to around 700°C. The effective absorption cross section of Er was dependent on the annealing temperature and was equal to 6.6×10−16cm2 for the sample annealed at 700°C. The strong Er-related photoluminescence is discussed in terms of a coupling phenomenon between Er3+ ions and spatially confined amorphous silicon clusters which act as sensitizers. The existence of a low annealing temperature to obtain the best Er-related photoluminescence is also discussed.