A large-scale lithography-free metasurface with spectrally tunable super absorption

Recently, periodically patterned metasurfaces have been employed to realize on-chip super/near-perfect optical absorption. However, most reported meta-absorbers rely on top-down micro/nano-lithography, which imposed a serious cost barrier on the development of practical applications, especially in the visible-infrared (IR) domain and at very large scales. Here we report a simple method to manufacture super absorptive metasurfaces using direct sputtering deposition. By controlling the deposition and post thermal treatment conditions, random metallic nanoparticles (NPs) can be formed easily on rigid and flexible substrates to function as the nanoantennas of spectrally tunable meta-absorbers. This low-cost and highly scalable approach would release the manufacturing barrier for previously reported meta-absorbers and therefore enable the development of affordable and large-scale thin-film metamaterial structures and devices.