Monolayer of Mie-Resonant Silicon Nanospheres for Structural Coloration

Abstract

Structural coloration of a monolayer of Mieresonant silicon (Si) nanospheres (NSs) produced by a solutionbased process is studied. It is shown by simulation that a monolayer of hexagonal close-packed Si NSs exhibits sizedependent structural color with a peak reflectance of ∼50%. The peak reflectance can be increased to over 90% by introducing spaces between the Si NSs. The high reflectance despite the small coverage is due to the very high scattering efficiency of Mieresonant Si NSs. Monolayers of densely packed Si NSs are produced from Si NS suspensions by the Langmuir−Blodgett method. The monolayers exhibit size-dependent structural color with a peak reflectance of 30−50%. The color is very insensitive to the viewing angle, and the angle dependence of the reflectance spectra is very small. The peak reflectance is increased by increasing the distance between the NSs by partially oxidizing the layers. The results demonstrate that iridescence-free structural coloration of a substance is possible by a layer of Si NSs much thinner than the monolayer, i.e., by sparsely scattered Si NSs.

Mie-Resonant Structural Color of Silicon Nanosphere Monolayer Coupled with Fabry–Pérot Cavity

“…However, as can be seen in Figure S7, the angle dependence is small. This is because of noniridescent structural color of Si NS monolayers . Finally, the structural color is stable in ambient for a long period (see Figure S6).…”

“…This results in the reflectance maximum at 550 nm due to the Kerker effect . The overlap of the two modes decreases with increasing g , and distinctive MD and ED peaks appear in the reflectance spectra when g = ∼100 nm …”

“…The oxide thickness is changed from 50 to 200 nm by the oxidation duration (see Figure S3). On the SiO 2 /Si substrates, Si NS monolayers are formed by the Langmuir–Blodgett (LB) method Figure g shows an SEM image of a Si NS monolayer.…”

“…Si NS monolayers were fabricated by the LB method . First, the Si NS surface was etched in HF solution (5 wt %) for 2 min to remove the native oxide and to make the surface hydrophobic, and then they were transferred to butanol.…”

Au–Si Nanocomposites with High Near-IR Light-to-Heat Conversion Efficiency via Single-Step Reactive Laser Ablation of Porous Silicon for Theranostic Applications

“…For example, switching to ultrashort (femtosecond) pulses commonly leads to a marked reduction of the LAL product size down to a few nanometers, yet making the synthesis substantially more expensive. At the same time, certain applications involving resonant light-matter interaction require an exact range of NP size that cannot be guaranteed upon variation of just laser parameters in the process of LAL synthesis …”