Emission dynamics of hybrid plasmonic gold/organic GaN nanorods

摘要

We studied the emission of bare and aluminum quinoline (Alq(3))/gold coated wurtzite GaN nanorods by temperature-and intensity-dependent time-integrated and time-resolved photoluminescence (PL). The GaN nanorods of similar to 1.5 mu m length and similar to 250 nm diameter were grown by plasma-assisted molecular beam epitaxy. Gold/Alq(3) coated GaN nanorods were synthesized by organic molecular beam deposition. The near band-edge and donor-acceptor pair luminescence was investigated in bare GaN nanorods and compared with multilevel model calculations providing the dynamical parameters for electron-hole pairs, excitons, impurity bound excitons, donors and acceptors. Subsequently, the influence of a 10 nm gold coating without and with an Alq(3) spacer layer was studied and the experimental results were analyzed with the multilevel model. Without a spacer layer, a significant PL quenching and lifetime reduction of the near band-edge emission is found. The behavior is attributed to surface band-bending and Forster energy transfer from excitons to surface plasmons in the gold layer. Inserting a 5 nm Alq(3) spacer layer reduces the PL quenching and lifetime reduction which is consistent with a reduced band-bending and Frster energy transfer. Increasing the spacer layer to 30 nm results in lifetimes which are similar to uncoated structures, showing a significantly decreased influence of the gold coating on the excitonic dynamics.