Near-IR (1 – 4 μm) control of plasmonic resonance wavelength in Ga-doped ZnO

The plasmonic resonance wavelength λres in ZnO doped with 3wt%Ga2O3 can be controlled over the range 1 – 4 μm by simple furnace annealing in flowing Ar. For each annealing temperature TA, the reflectance Rm and transmittance Tm are measured over a wavelength range, λ = 185 – 3200 nm, (energy range, E = 6.7 – 0.387 eV), and the reflectance coefficient R is calculated from Rm and Tm. The value of λres is then determined from a Drude-theory analysis of R vs E that yields fitting parameters nopt (optical carrier concentration), μopt (optical mobility), high-frequency dielectric constant ε∞, and thickness d, at each annealing temperature TA. The validity of this process is confirmed by comparison of ε∞ with literature values, and comparison of nopt and μopt with analogous quantities n and μH measured by the Hall-effect.