Generation of Reflection Colors from Metal–Insulator–Metal Cavity Structure Enabled by Thickness-Dependent Refractive Indices of Metal Thin Film

Abstract

Tunable structural colors have diverse applications ranging from displays and photovoltaics to surface decoration and art. A metal−insulator−metal (MIM) cavity structure formed by thin continuous layers has drawn great interest as a lithography-free and scalable optical structure to control light transmission and reflection at the surface of a material. However, the production of distinct reflection colors from the structure is challenging because the typical MIM cavity absorbs a narrow wavelength range and reflects the rest of the spectrum. This study shows that the MIM structure can exhibit a reflection peak instead of a reflection dip if the metal layer has proper optical constants. Vivid reflection colors are generated by using thermally evaporated Au and Ag thin films whose refractive indices are much different from the standard handbook data. The strong thickness dependence of the refractive indices also enables color tuning by varying the thickness of the metal layer only. Consequently, color images can be printed by locally controlling the thickness of either the insulating spacer or the metal layer. The results of the study are attractive and useful for both practical and artistic purposes.

High-purity reflective color filters based on thin film cavities embedded with an ultrathin Ge2Sb2Te5 absorption layer

“…21,27 Thin lms may have refractive indices different from the bulkstate handbook data. In a previous report, 19 we showed that the refractive indices of Au and Ag lms deposited by thermal evaporation are strongly thickness dependent and coincide with the handbook data only for thicknesses over 40 nm. For a 10 nm-thick Au lm, the real part of the refractive index was comparable to its imaginary part at wavelengths longer than 600 nm, being highly lossy in this spectral range.…”

“…A Fabry-Perot (F-P) cavity comprising metalinsulator-metal (MIM) continuous layers is of signicant interest as a lithography-free planar structure for controlling the transmission, reection, and absorption of light. [19][20][21][22][23][24][25][26][27] In transmission mode where both metal layers are sufficiently thin (i.e., semitransparent), the cavity can selectively transmit a narrow frequency range of incident light, thus producing fairly vivid transmissive colors. The colors are tunable by varying the thickness of the insulator layer (i.e., the dielectric spacer).…”

Reflective Coloration from Structural Plasmonic to Disordered Polarizonic

“…Consequently, the arrangement of the dipoles within a matrix does not affect or vary the specular reflection, yet the main contribution emerges from the dynamic polarizability of the arbitrary nanoparticles within the glassy medium as demonstrated by us [ 37,38,98 ] and adapted by other researchers. [ 99,100 ]…”

“…Consequently, the arrangement of the dipoles within a matrix does not affect or vary the specular reflection, yet the main contribution emerges from the dynamic polarizability of the arbitrary nanoparticles within the glassy medium as demonstrated by us [37,38,98] and adapted by other researchers. [99,100] The complex refractive index (RI) of the effective medium of the nanocomposite plays a crucial role in the optical behavior of the stacked system. In this regard, the imaginary part "k" is governed by absorption, thus engendering the well-known plasmonic colors.…”

Nanostructured Color Filters: A Review of Recent Developments

“…Although [ 49 , 50 ] showed promising results, managing thin lossy metals requires special treatment. Recently, a broadband light absorber was constructed with absorption in the visible region by utilizing thermally evaporated Ag and Au layer [ 42 ] ( Figure 2 B), which exhibit refractive indices much different from the bulk-state value [ 51 ]. Nevertheless, the angle invariance was high, i.e., up to .…”