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

Abstract

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 mid‐infrared (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. It is shown that this fabrication technique can provide a bottom‐up approach to controlling the length and spacing of the design. The characterization findings reveal a broadband absorbance above 0.8 in vis and NIR, and a narrowband absorbance centered around 6.54 µm. Dense architecture and extraordinary permittivity of Bi provide strong field confinement in ultrasmall gaps between nanostructures, and this can be utilized for a sensing application. An ultrahigh sensitivity of 2151 nm refractive‐index unit (RIU–1) is acquired, which is, as far as it is known, the experimentally highest sensitivity attained so far. The simple and large‐scale compatible fabrication route of the design together with the extraordinary optical response of Bi coating makes this design promising for many optoelectronic and sensing applications.

Ultra-broadband, lithography-free, omnidirectional, and polarization-insensitive perfect absorber

“…Yet, those sub-wavelength patterns demand lithographic fabrication, which are costly and cumbersome, especially for the applications of large surface areas and high working frequencies (i.e., tiny feature sizes). Therefore, the fabrication of PAs without the use of EB lithography, such as multilayer deposition 23 – 31 , oblique-angle deposition 32 , 33 , and chemical processes 34 – 36 , has been proposed to overcome the drawbacks of structural metamaterials. Among those methods, the multilayer deposition method outperforms others because the multilayer deposition method is not only more feasible, but also achieves the larger bandwidth and higher incident angle tolerance simultaneously.…”

Strong Light–Matter Interactions in Au Plasmonic Nanoantennas Coupled with Prussian Blue Catalyst on BiVO4 for Photoelectrochemical Water Splitting

“…Moreover, the simultaneous formation of small and large particles could excite both FP and LSPR modes to achieve both semiconductor light absorption enhancement and plasmonic hot electron injection. In recent studies, we developed a facial route based on oblique angle deposition to synthesize plasmonic nanostructures on a large scale. Moreover, we demonstrated that as a result of the cyanide chemistry, so‐called CoFe‐Prussian blue analog (PBA) is a strong and robust water oxidation catalyst (WOC), when connected to an organic chromophore .…”

Ultra-broadband Near-Unity Light Absorption by Disjunct Scattering Resonances of Disordered Nanounits Created with Atomic Scale Shadowing Effect

“…It is generally accepted that the mechanistic factor controlling the nanostructural evolution of the films is an atomic scale "shadowing effect," which prevents the deposition of particles in regions situated behind initially formed nuclei (i.e., shadowed regions). We have successfully adopted this approach for the design of 3D ultra-broadband absorbers in visible, near-infrared (NIR) [53][54][55] and mid-infrared (MIR) [56,57] light-harvesting devices. Taking all into consideration, the oblique angle deposition, with its random geometry and capability to synthesize nanostructures with no material restriction, is an excellent approach to realize high-performance perfect absorbers in large-scale dimensions.…”