Film Thickness Dependence of Surface Plasmon Resonance Behavior at a Grating Structure of Highly Ga-Doped ZnO

摘要

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