Er3+ interlayer energy migration as the limiting photoluminescence quenching factor in nanostructured Er3+:Y2O3 thin films

We report the effects of Er3+ nanostructuring on optical properties of heterogeneously doped Er3+:Y2O3 thin films synthesized by radical enhanced atomic layer deposition. By alternating the cycle sequences of Y2O3 and Er2O3, rare earth (RE) ion concentrations were controlled from 4.8 to 11.8 at. % Er and the local Er2O3 thicknesses were varied between 0.7 to 7.6 angstrom. Photoluminescence (PL) was used to examine the 1535 nm (Er I-4(13/2) -> I-4(15/2)) emission at two excitation wavelengths, 488 nm and 976 nm. The normalized PL increased with increasing Er3+ concentrations up to 11.8 and 9.6 at. % under 488 and 976 nm excitations, respectively. The introduction of a local Er2O3 layer greater than 2.4 angstrom resulted in significant PL quenching, over an order of magnitude, under both excitation wavelengths. The quenching was attributed to enhanced local Er3+<-> Er3+ interlayer energy migration. Compared to homogeneously doped RE systems where the RE concentration is directly related to the average RE <-> RE spatial distance, increased luminescence was observed at high Er3+ concentrations in heterogeneously doped systems. These results suggest that controlling the RE proximity is key to engineering the optical properties of RE doped heterogeneous materials. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737793]