Surface-plasmon mediated photoluminescence enhancement of Pt-coated ZnO nanowires by inserting an atomic-layer-deposited Al₂O₃ spacer layer.

Surface-plasmon mediated photoluminescence emission enhancement has been investigated for ZnO nanowire (NW)/Pt nanoparticle (NP) nanostructures by inserting an Al2O3 spacer layer. The thickness of the Al2O3 spacer layer and of the Pt NPs capped on the ZnO NWs are well controlled by atomic layer deposition. It is found that the photoluminescence property of the ZnO NW/Al2O3/Pt hybrid structure is highly tunable with respect to the thickness of the inserted Al2O3 spacer layer. The highest enhancement (∼14 times) of the near band emission of ZnO NWs is obtained with an optimized Al2O3 spacer layer thickness of 10 nm leading to a ultraviolet-visible emission ratio of 271.2 compared to 18.8 for bare ZnO NWs. The enhancement of emission is influenced by a Förster-type non-radiative energy transfer process of the exciton energy from ZnO NWs to Pt NPs as well as the coupling effect between excitons of ZnO NWs and surface plasmons of Pt NPs. The highly versatile and tunable photoluminescence properties of Pt-coated ZnO NWs achieved by introducing an Al2O3 spacer layer demonstrate their potential application in highly efficient optoelectronic devices.