Metallic Nanodimple Arrays for Wide-Angle Coloration via Plasmonic and Structural Resonances

Plasmonic metasurfaces have provided unique optical properties useful for high-resolution color printing, reflective or transmissive displays, color filters, sensors, and anticounterfeiting. However, direct-writing methods to produce the metasurfaces have a low production throughput, and self-assembly approaches have limited control over optical property and resolution of patterning. Here, we design multicolor graphics by combining bottom-up colloidal self-assembly and top-down photolithography. Hexagonal arrays of nanodimples are templated by two-dimensional (2D) colloidal crystals to develop both plasmonic and structural colors after aluminum deposition, and the nanodimples can be reshaped by thermal annealing to tune the plasmonic colors. In addition, the nanodimple arrays can be micropatterned to have single- or dual-colored graphics by a photolithographic technique. The graphics show angle-independent plasmonic colors for specular reflection. At the same time, the graphics show angle-dependent structural colors for a wide range of observation angles through diffraction on the polycrystalline hexagonal arrays. The simultaneous use of plasmonic and structural resonances makes the graphics show high visibility. In addition, the fabrication procedure is relatively simple, reproducible, and scalable. We believe that plasmonic graphics will be potentially useful for optical encoding and anticounterfeiting.