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 co-doped 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.