Fluorine-doped tin oxides for mid-infrared plasmonics

Abstract

Fluorine-doped tin oxides (FTO) were investigated for infrared plasmonic applications. Nano-crystalline FTO thin films were grown by the SPEED chemical-spray deposition method. Complex permittivity spectra were measured from 1.6 to 12 μm wavelength. These spectra were used to calculate materials parameters, which compared well with values from transport measurements, and to predict characteristics of surface plasmon polaritons (SPP). Reflectivity spectra for lamellar FTO gratings revealed SPP coupling resonances in good agreement with predictions. The FTO film studied here is well suited for plasmonic applications in the important 3-5 μm wavelength range.