Enhancement of ZnO photoluminescence by localized and propagating surface plasmons

Insulating spacer layers of MgO were used to identify the enhancement mechanisms of the ZnO band-edge and visible luminescence in ZnO-MgO-Ag and ZnO-MgO-Au multilayers. Purcell enhancement of the ZnO band-edge emission by both Ag and Au surface plasmon polaritons is confirmed by demonstrating that the exponential decay of this emission as a function of increasing MgO thickness is consistent with the Ag and Au SPP evanescent decay lengths. Local surface plasmons excited in Ag and Au nanoparticles and rough films are also shown to enhance the ZnO visible donor-acceptor-pair photoluminescence by dipole-dipole scattering, again with an appropriate dependence on the thickness of the MgO spacer layer. We also confirm that both Ag and Au nanoparticles enhance the ZnO band-edge emission by charge transfer when the MgO spacer layer is absent.