Nanostructuring the Er3+ and Si nanoparticle distributions to enhance the 1.5 μm emission in codoped Al2O3 thin films

Nanostructured amorphous aluminum oxide (Al₂O₃) thin films codoped with Erbium ions (Er³⁺) and Si nanoparticles (Si NPs) are prepared by pulsed laser deposition. The doping structure can be controlled in such a way that Er³⁺ and Si NP concentrations are optimized independently, the Si NP sizes are selected and the Er³⁺ and Si NPs distances are varied to achieve a close contact below the nanometer scale. The optimized as-grown films show an enhanced photoluminescence performance at 1.5 μm which is related to an efficient Si NPs to Er³⁺ energy transfer. Upon low temperature thermal annealing it is found a further enhancement of the photoluminescence intensity which is due both to a decrease of the number of non-radiative defects in the film and to an increase the fraction of excitable Er³⁺ ions through Si NPs. The origin of the loss of the Si NPs-Er energy transfer upon high temperature annealing (≥750°C) is discussed.