Patterned resist on flat silver achieving saturated plasmonic colors with sub-20-nm spectral linewidth

Plasmonic color generation is a promising field of study that have the potential to produce paradigm-shifts in display and printing technologies. To produce vibrant colors, plasmonic surfaces decorated with complex corrugated or protruding structures have been the commonly adopted strategy for saturated structural color generation. However, it is particularly challenging to cover the full sRGB color gamut due to difficulty in achieving narrowband spectral response via plasmonic structures. Here we report a flat silver film decorated with 90 nm-thick resist nanostructures of low aspect-ratio feature (0.25-0.55). With such a facile and close-to-uniform morphology, we experimentally demonstrate sub-20-nm linewidth of full-width-half-maxima (FWHM) of reflection spectra in the visible range, realizing a color gamut comparable to that of ultra-high definition TV (UHDTV) in the chromaticity diagram. Our work breaks the conventional notion that sophisticated and high aspect-ratio plasmonic and dielectric nanostructures are indispensable, and highly saturated color are impossible for plasmonic nanoprinting. The unique structure enables an etch-free fabrication and recycling recipe, with the potential for mass production by nanoimprinting lithography and other applications including multicolor holographic projection.