Film Thickness Dependence Of Surface Plasmon Resonance Behavior At A Grating Structure Of Highly Ga-Doped Zno

Grating structures of the same grating period and similar ridge widths and heights are fabricated at the air interface of highly Ga-doped ZnO (GaZnO) thin films of different thicknesses for studying the different resonance behaviors of induced surface plasmon (SP) polariton and localized SP in the near-IR range. The wavelengths of those SP resonance modes obtained via the reflection and transmission measurements from the air and substrate sides are compared for observing the effects of the GaZnO/substrate interface on the behaviors of the SP resonances induced around the grating structures. With the refractive index of the sapphire substrate around 1.75, the resonance wavelengths of the SP modes induced in a sample of a smaller GaZnO film thickness generally become longer. This variation trend can be clearly observed in the reflection measurement from the sapphire side. Therefore, the SP resonance wavelengths of a GaZnO grating structure can be controlled by the refractive index of the used substrate as long as the GaZnO layer is not too thick (roughly thin than 200 nm).