Abstract
We experimentally demonstrated an amorphous graphene-based metasurface yielding near-infrared super absorber characteristic. The structure is obtained by alternatively combining magnetron-sputtering deposition and graphene transfer coating fabrication techniques. The thickness constraint of the physical vapor-deposited amorphous metallic layer is unlocked and as a result, the as-fabricated graphene-based metasurface absorber achieves near-perfect absorption in the near-infrared region with an ultra-broad spectral bandwidth of 3.0 µm. Our experimental characterization and theoretical analysis further point out that the strong light-matter interaction observed is caused by localized surface plasmon resonance of the metal film's particle-like surface morphology. In addition to the enhanced light absorption characteristics, such an amorphous metasurface can be used for surface-enhanced Raman scattering applications. Meanwhile, the proposed graphene-based metasurface relies solely on CMOS-compatible, low cost and large-area processing, which can be flexibly scaled up for mass production.
Highlights
In recent times, there have been a growing interest in perfect absorbers or so-called super absorbers, which fully absorb electromagnetic radiations at specific wavelengths ranging from the visible to infrared regions, owing to their potential in enhancing performances in solar energy conversion [1,2], thermal imaging [3], thermophotovaltaics [4], and sensors [5]
Multilayer coatings lead to thicker optical devices, and the current trends for realizing such perfect absorbers resort to so-called metasurfaces, which are nanostructures with controlled geometry and periodicity that are easy to implement into downscaled optical components
To improve the graphene transfer coating, we carry out a pre-study of chemical vapor deposition (CVD) grown graphene transfer process on SiO2/Si wafer, and we found that the backside surface of CVD-grown graphene on copper needs to be removed to minimize the defects and improve the monolayer graphene’s uniformity, as discussed in Figs. 6(a)–6(b) of Appendix A
Summary
There have been a growing interest in perfect absorbers or so-called super absorbers, which fully absorb electromagnetic radiations at specific wavelengths ranging from the visible to infrared regions, owing to their potential in enhancing performances in solar energy conversion [1,2], thermal imaging [3], thermophotovaltaics [4], and sensors [5]. With the flexibility of current state-of-the-art nanofabrication approaches, recent developments of metasurfaces [8] can yield near perfect light absorption in the visible [9], near-infrared [10], mid-infrared [11], and far-infrared [12] regions Among these perfect absorbers, the three-layer configuration is designed with a metasurface on the top, a dielectric spacer in the middle, and a metallic reflector at the bottom, which is analogous to so-called Salisbury screen [13]. In addition to the light absorption enhancement, such metasurfaces have a potential in surface enhanced Raman scattering applications, as indicated by characterizing sandwiched graphene with metasurfaces
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