Coupling of photoluminescent centers in ZnO to localized and propagating surface plasmons

The interaction of excitons and other photoluminescent centers in semiconductors with plasmons represents the coupling of the fundamental one-particle, electron-hole excitation with the fundamental many-particle excitation in metals. We describe recent photoluminescence and pump-probe experiments that illustrate both the energetics and the dynamics of this interaction, in a model material incorporating ZnO films separated from a nanostructured plasmonic metal substrate by a variable-thickness spacer layer. We find evidence for different coupling mechanisms for the band-edge exciton and donor–acceptor pair defect luminescence, and discuss the competing roles of localized surface-plasmon resonances and propagating surface-plasmon polaritons. We also present first femtosecond pump-probe lifetime measurements for the band-edge exciton with and without the presence of nearby metal nanostructures.