The effects of energy transfer on the Er3+ 1.54 μm luminescence in nanostructured Y2O3 thin films with heterogeneously distributed Yb3+ and Er3+ codopants

Abstract

We report the effects of heterogeneous Yb3+ and Er3+ codoping in Y2O3 thin films on the 1535 nm luminescence. Yb3+:Er3+:Y2O3 thin films were deposited using sequential radical enhanced atomic layer deposition. The Yb3+ energy transfer was investigated for indirect and direct excitation of the Yb 2F7/2 state using 488 nm and 976 nm sources, respectively, and the trends were described in terms of Forster and Dexter's resonant energy transfer theory and a macroscopic rate equation formalism. The addition of 11 at. % Yb resulted in an increase in the effective Er3+ photoluminescence (PL) yield at 1535 nm by a factor of 14 and 42 under 488 nm and 976 nm excitations, respectively. As the Er2O3 local thickness was increased to greater than 1.1 Å, PL quenching occurred due to strong local Er3+ ↔ Er3+ excitation migration leading to impurity quenching centers. In contrast, an increase in the local Yb2O3 thickness generally resulted in an increase in the effective Er3+ PL yield, except when the Er2O3 and Yb2O3 layers were separated by more than 2.3 Å or were adjacent, where weak Yb3+ ↔ Er3+ coupling or strong Yb3+ ↔ Yb3+ interlayer migration occurred, respectively. Finally, it is suggested that enhanced luminescence at steady state was observed under 488 nm excitation as a result of Er3+ → Yb3+ energy back transfer coupled with strong Yb3+ ↔ Yb3+ energy migration.