Enhancement of Er³⁺ Emission from an Er−Si Codoped Al₂O₃ Film by Stacking Si−Doped Al₂O₃ Sublayers

A multilayer film (multi-film), consisting of alternate Er-Si-codoped Al₂O₃ (ESA) and Si−doped Al₂O₃ (SA) sublayers, is synthesized by co−sputtering from separated Er, Si, and Al₂O₃ targets. The dependence of Er³⁺ related photoluminescence (PL) properties on annealing temperatures over 700–1100°C is studied. The maximum intensity of Er³⁺ photoluminance (PL), about 10 times higher than that of the monolayer film, is obtained from the multi−film annealed at 950°C. The enhancement of Er³⁺ PL intensity is attributed to the energy transfer from the silicon nanocrystals (Si−NCs) to the neighboring Er³⁺ ions. The effective characteristic interaction distance (or the critical ET length) between Er and carriers (Si−NCs) is ∼3 nm. The PL intensity exhibits a nonmonotonic temperature dependence. Meanwhile, the PL integrated intensity at room temperature is about 30% higher than that at 14 K.