Study of NBE emission enhancement of ZnO nanorods by changing the surface property of ultrathin Ag interlayer

Surface plasmon-enhanced near-band-edge (NBE) emission of ZnO nanorods (NRs) array was studied after growing on ultra-thin Ag film of mass thickness 1 nm. Prior to the growth, Ag films were annealed at 100 and 250 °C. Annealing at 100 °C lead to the formation of smaller size of Ag nanoparticles with higher particle number density facilitating the vertical growth of higher density of ZnO NRs with high aspect ratio. The observation of predominant (002) plane from X-ray diffraction confirmed the preferential growth of ZnO nanorods on Ag films. The shape, orientation, diameter and number particles density of ZnO NRs are investigated by scanning electron microscopy (SEM). The photoluminescence (PL) spectra reveals the enhancement of NBE emission of ZnO NRs due to the transfer of electrons from Ag to ZnO and the resonance coupling of surface plasmon energy with ZnO emission. The evolution of multiple, low intense side bands in visible rsgion are due to shallow trap levels. Moreover, the absence of broad defect level emission peak indicating the high optical quality of ZnO NRs which could be applicable for UV LEDs.