Figure shows the reflectance R, ratios of cross sections σ abs /σ sca , σ abs , and σ sca plots for the data with the lowest reflectance condition from the comprehensive FDTD simulation results. For Au, Ag, and Cu, the peaks of the σ abs and σ sca are coincident, and they are equal to each other at the reflectance minimum (σ abs /σ sca ∼ 1). In contrast, for HEA, Pt, and Pd, the σ abs and σ sca peaks appeared at separate wavenumbers, indicating that the σ abs is much larger than the σ sca at the resonance wavelength of low reflection where absorption is dominant. To examine this in more detail, the ratio of the σ abs and σ sca (σ abs /σ sca ) at each resonant wavelength is plotted against the reflectance (Fig. ). In the case of Au, Ag, and Cu, the minimum reflection appeared at σ abs /σ sca =1 in all simulation results for different SiO 2 thickness. Therefore, all data, including Au, Ag, Cu, and different SiO 2 thicknesses, can be plotted as a single Gaussian function, which is presented by the dotted gray line. HEA and Pt also follow this relationship when SiO 2 thickness is from 50 to 150 nm. However, when a thicker SiO 2 film was used, σ abs /σ sca > 1 was observed. At this condition, the absorption becomes dominant and corresponds well with the experimental reflection spectra. In the case of Pd, the shift value of σ abs /σ sca is the largest in all metals. This indicates the strong absorption of metals decreases the Q-factor of the MIM resonance. The shifted σ abs /σ sca value is similar to that of 50 nm Cr added as an adhesion layer, shown in our previous work . These results indicates that HEA with Au, Ag, Cu, Pd, and Pt realizes the "true perfect absorption" and "true perfect thermal emission."