Reflection structural colors based on Fano resonance in planar optical nanocavities with Sb2Te3 layer

Planar optical nanocavities play crucial roles in light interactions with matters and structural colors. The purity of reflection structural color is generally limited by the resonant absorption of light, especially in metal-based nanocavities. Herein, we propose and fabricate a novel kind of planar metal-based nanocavities integrated with an ultrathin antimony telluride (Sb₂Te₃) layer to generate Fano resonance effect for achieving the vivid reflection colors, which present the higher purity than those of traditional metal/dielectric/metal cavities. The results show that the Sb₂Te₃/ITO/Ag nanofilm possesses strong light absorption in the entire visible region. The integration of this nanofilm with the ITO and Ag layers can give rise to the generation of Fano resonance effect with the low light absorption and narrow reflection peak. The experiments agree excellently with the simulations. The Fano resonance effect can be derived from the coupling interference between the wide-spectrum lossy resonance (continuum state) in Sb₂Te₃/ITO/Ag nanofilm and narrow-spectrum resonance (discrete state) in Ag/ITO/Ag nanocavity. We achieve the high-purity reflection structural colors in the planar nanocavities and vivid color printing based on the Fano resonance effect by using grayscale focused ion beam (FIB) lithography. This work will pave a new avenue for the realization of Fano resonance and its application in high-performance reflection color printing.