Tuning the metal filling fraction in metal-insulator-metal ultra-broadband perfect absorbers to maximize the absorption bandwidth

Abstract

In this paper, we propose a methodology to maximize the absorption bandwidth of a metal-insulator-metal (MIM) based absorber. The proposed structure is made of a Cr-Al 2 O 3-Cr multilayer design. At the initial step, the optimum MIM planar design is fabricated and optically characterized. The results show absorption above 0.9 from 400 nm to 850 nm. Afterward, the transfer matrix method is used to find the optimal condition for the perfect light absorption in an ultra-broadband frequency range. This modeling approach predicts that changing the filling fraction of the top Cr layer can extend light absorption toward longer wavelengths. We experimentally proved that the use of proper top Cr thickness and annealing temperature leads to a nearly perfect light absorption from 400 nm to 1150 nm, which is much broader than that of a planar design. Therefore, while keeping the overall process lithography-free, the absorption functionality of the design can be significantly improved. The results presented here can serve as a beacon for future performance-enhanced multilayer designs where a simple fabrication step can boost the overall device response without changing its overall thickness and fabrication simplicity.

Semiconductor-nanoantenna-assisted solar absorber for ultra-broadband light trapping

“…Solar energy, as a renewable, clean, and widespread energy, is widely studied because it can be transformed into other energies for wide applications such as solar cells [1][2][3], photovoltaic devices [4,5], and photothermal emitters [6,7]. Since Landy et al reported the perfect absorbers based on the metal-insulator-metal triple-layer meta-materials [8], a plenty of fascinating nanostructures have been designed for the collection and utilization of solar energy [9][10][11][12][13][14][15][16][17][18][19][20][21]. It is worth noting that the efficient solar energy capture is a key for these applications.…”

“…However, the absorbed solar energy would lead to the increase in temperature (i.e., thermal instability), resulting in the damage of noble metallic nanostructures with low melting point [7]. Note that the structural stability and high temperature tolerance can be guaranteed when refractory metals are used to replace noble metals in the absorbers [6,9,11,12]. Although the broadband light absorption phenomena were demonstrated in these platforms, these methods may suffer from problems such as the sophisticated geometries [6,18], relatively finite absorption bandwidths (< 750 nm) [9,11,12], or large requirement of noble metals [8,10,11,18].…”

Lithography‐Free Random Bismuth Nanostructures for Full Solar Spectrum Harvesting and Mid‐Infrared Sensing

“…To alleviate these problems, planar multilayer designs that consist of metal–insulator (MI) pairs are proposed. Many multilayer planar structures were designed and fabricated using this idea . Although this architecture provides a lithography‐free fabrication route and broadband response, the absorbed power is not accessible due to being confined mostly in the middle metallic layer.…”

“…Many multilayer planar structures were designed and fabricated using this idea. [18][19][20][21][22][23][24][25] Although this architecture provides a lithography-free fabrication route and broadband A lithography-free, double-functional single bismuth (Bi) metal nanostructure is designed, fabricated, and characterized for ultrabroadband absorption in the visible (vis) and near-infrared (NIR) ranges, and for a narrowband response with ultrahigh refractive index sensitivity in the midinfrared (MIR) range. To achieve a large-scale fabrication of the design in a lithography-free route, the oblique-angle deposition approach is used to obtain densely packed and randomly spaced/oriented Bi nanostructures.…”

Lithography-free, manganese-based ultrabroadband absorption through annealing-based deformation of thin layers into metal–air composites

“…Therefore, it has always been very desirable to come up with lithography-free, cost-effective, and easy-to-fabricate structures. Some of the designs for lithography-free absorbers are based on planar MIM cavities [6,7], metal-insulator multilayer stacks [8], chemically synthesized metal-coated dielectric nanowires [9], random nanopillars [10], and etching-based random pyramids formed in doped Silicon wafers [11]. In addition, lithography-free absorbers without a broadband response are also of high interest, and they cover a wide range of crucial applications such as filtering [12], real-time tuning [13], and bio-sensing [14].…”