In discussions of experimental data, it is often argued that 2 nm of Cr have enough adhesion strength for successful lift-off. Thinner Au at less than 10 nm would be expected to form an island film rather than an uniform coating. Therefore, a 2 nm of Cr and 10 nm Au defines the lowest limitation for experimental fabrication. Therefore the transparency of 40% that has been obtained in experiments is almost the limitation using Au as the ground plate in MIM metasurfaces. Figure (a) shows optical permittivity of Au, Cr and Ti that has obtained from Palik's database and used for the FDTD simulations.