Surface plasmon modes guided by Ga-doped ZnO layers bounded by different dielectrics

We report two types of surface plasmon (SP) modes guided by a Ga-doped ZnO (ZnO:Ga) layer bounded between air and glass. A symmetric SP (s-) mode having leaky waves was found at an air-ZnO interface by attenuated total reflection measurements and showed a cutoff thickness region from 141 to 107 nm. Consequently, only an asymmetric SP (a-) mode bound at a ZnO-glass interface remained, as confirmed by numerical analyses and finite-difference time-domain simulations. s- and a-modes of the ZnO:Ga layer exhibited a high cutoff thickness and a strongly confined SP field at air-ZnO and ZnO-glass interfaces, respectively.