Surface-plasmon-enhanced visible light emission of ZnO/Ag grating structures

We investigated the optical properties of ZnO/Ag grating structures, with the periods of 1000 and 1400 nm, fabricated by sputtering and nanoimprint lithography. The grating structures exhibited multiple peak features in visible-range photoluminescence (PL) spectra. Whereas a ZnO/Ag planar thin film showed two broad PL peaks in UV and visible region. Moreover, the PL intensity of the periodic structures was similar to 100 times larger than that of the planar counterpart. Several reflectance dips in the visible range were seen only in the grating structures, which could be caused by photon-induced surface plasmon polariton (SPP) excitation via the grating coupling. The PL peaks well matched with the reflectance dips. This represented that the PL enhancement should be originated from the SPP excitation. The finite-difference time-domain simulations also supported the plasmonic effects in the periodic structures.