Localized surface plasmon enhanced photoluminescence from ZnO films: Extraction direction and emitting layer thickness

The light emission from ZnO films is enhanced by localized surface plasmon (LSP) of Ag island films. The dependence of LSP coupled emission on light-extracting direction and the thickness of ZnO films is investigated. It is found that the photoluminescence (PL) enhancement factors for upward extraction are much smaller than those for downward extraction. This is ascribed to the low transmittance and nonradiative absorption loss of Ag films. The near-field effect of LSP results in the dependence of the PL enhancement of ZnO films on the film thickness. A maximum PL enhancement factor of more than 15 is obtained when the thickness of ZnO was about 40 nm.