Structural Color Filters Enabled by a Dielectric Metasurface Incorporating Hydrogenated Amorphous Silicon Nanodisks

Chul-Soon Park,Song Gao,Vivek Raj Shrestha,Duk-Yong Choi,Wenjing Yue,Sang-Shin Lee,Eun-Soo Kim

doi:10.1038/s41598-017-02911-w

Chul-Soon Park, Song Gao + Show 5 more

Open Access

https://doi.org/10.1038/s41598-017-02911-w

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Abstract

It is advantageous to construct a dielectric metasurface in silicon due to its compatibility with cost-effective, mature processes for complementary metal-oxide-semiconductor devices. However, high-quality crystalline-silicon films are difficult to grow on foreign substrates. In this work, we propose and realize highly efficient structural color filters based on a dielectric metasurface exploiting hydrogenated amorphous silicon (a-Si:H), known to be lossy in the visible regime. The metasurface is comprised of an array of a-Si:H nanodisks embedded in a polymer, providing a homogeneously planarized surface that is crucial for practical applications. The a-Si:H nanodisk element is deemed to individually support an electric dipole (ED) and magnetic dipole (MD) resonance via Mie scattering, thereby leading to wavelength-dependent filtering characteristics. The ED and MD can be precisely identified by observing the resonant field profiles with the assistance of finite-difference time-domain simulations. The completed color filters provide a high transmission of around 90% in the off-resonance band longer than their resonant wavelengths, exhibiting vivid subtractive colors. A wide range of colors can be facilitated by tuning the resonance by adjusting the structural parameters like the period and diameter of the a-Si:H nanodisk. The proposed devices will be actively utilized to implement color displays, imaging devices, and photorealistic color printing.

Highlights

One of the outstanding applications of such a metasurface may be a structural color filter that operates in the visible regime, which is regarded as a promising alternative for pigment/dye-based colorations in the applications encompassing color displays, imaging, color printing, photovoltaic, and so forth[12,13,14,15]
The operation of the proposed metasurface was thoroughly explored through the observation of the field profiles, which are accountable for the electric dipole (ED) and magnetic dipole (MD) resonances initiated by the amorphous silicon (a-Si):H nanodisk
The proposed filters were designed by means of a simulation tool that is based on the finite-difference time-domain (FDTD) method (FDTD Solutions, Lumerical, Canada)

Summary

Introduction

One of the outstanding applications of such a metasurface may be a structural color filter that operates in the visible regime, which is regarded as a promising alternative for pigment/dye-based colorations in the applications encompassing color displays, imaging, color printing, photovoltaic, and so forth[12,13,14,15]. As against the case of c-Si, amorphous silicon (a-Si) is presumed to offer a salient advantage that it can be efficiently grown over a foreign substrate at a low temperature so as to exhibit a high refractive index and be appreciably compatible with the cost-effective complementary metal-oxide-semiconductor (CMOS) process In this context, several color filtering schemes were suggested relying on either a high-index film or a nanodisk in a-Si, yet the transmission was unbearably poor or the operation was limited to the reflective mode due to its high absorption in the visible band[20, 21, 39, 40]. The operation of the proposed metasurface was thoroughly explored through the observation of the field profiles, which are accountable for the ED and MD resonances initiated by the a-Si:H nanodisk

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Conclusion