Enhanced photoluminescence of rare-earth doped films prepared by off-axis pulsed laser deposition

Alternate pulsed laser deposition from the host (Al2O3) and dopant (Er, Yb) targets has been used to prepare artificially nanostructured films in which the rare earth ion-ion separation is controlled in the nanometer scale in order to control energy transfer between ions. One series of films was prepared in the standard on-axis configuration, i.e. a static substrate being centred with respect to the plasma expansion axis. A second series of films was prepared by rotating the substrate with respect to a shifted axis parallel to the plasma expansion one (off-axis configuration). The latter configuration leads to films with enhanced thickness and Er related photoluminescence intensity uniformity. More interestingly, the Er related photoluminescence lifetime in as-grown films increases up to 2.5 ms, which is much higher than the maximum value of 1 ms obtained for the on-axis configuration films. This enhancement is discussed in terms of a decrease of defect density when using the off-axis configuration.

Research highlights▶ PLD off-axis configuration provides larger film uniformity and enhanced PL lifetime for Er-doped as-grown thin films. ▶ PLD off-axis enables to decrease the impact of high kinetic energy species at the substrate centre, and consequently there is a decrease of induced defects. ▶ PLD off-axis configuration opens a route to prepare rare-earth doped materials with low defect densities and reduced Er-Er interaction.