Influence of annealing on the structure and 1.54 μm photoluminescence of er-doped ZnO thin films prepared by sol-gel method

We have investigated the effects of Er concentration, post-annealing time and temperature through a sol-gel preparation method on the structure and 1.54-μm-related photoluminescence (PL) of ZnO:Er thin films. The results illustrated that the 1.54μm emission was greatly influenced by the local structure of Er-O complex and ZnO host. The active oxygen movement during annealing process resulted in the formation of optical active center of Er ions, which probably attributed to the formation of a similar pseudo-octahedron with C_4v structure around Er. The preferential orientation of ZnO host had more effect on the 1.54 μm PL intensity than the crystallinity of ZnO host. Therefore, the optimum annealing condition was about 800 °C/2 h and the appropriate concentration was about 0.05 at. % Er. A low-cost and fast formation of highly efficient Er centers in ZnO host for strong luminescence at near-infared region should be benefit for both fundamental research and also applications of light-emitting devices.