Improving the photoluminescence of thin films by nanostructuring the rare-earth ion distribution

Pulsed laser deposition has been used to prepare nanostructured rare-earth-doped films. Alternate deposition from the host (Al2O3) and dopant (Er, Yb) targets has been used to obtain artificially structured films in which the rare-earth ion–ion separation is controlled in the nanometer scale (0.5–9 nm). In the case of Er3+–Er3+ interactions, it has been found that self-quenching is greatly reduced for separations larger than 3 nm. The control of the laser fluence used for Er ablation is also important, and higher fluences lead to higher luminescence efficiencies. The Er and Yb co-doped films have been designed with the Er3+ and Yb3+ ions distributed either in the same layer or in different layers separated from 1 to 3 nm. The emission intensity in these codoped films can be up to two orders of magnitude higher than that reported for films doped only with Er. The results evidence that structuring the rare-earth distribution in the nanometer scale is a very efficient means to reduce rare-earth clustering. Finally, it will also be shown that nanostructuring offers a valuable method to analyze ion–ion interactions such as energy transfer mechanisms.