The combination of quantum materials and metasurfaces promises intrinsically new functionalities, driven by the wide range of novel phenomena inherent to quantum materials and the ability to control them with metamaterials. Two-dimensional (2D) quantum materials, such as graphene and transition metal dichalcogenides, have attracted much attention in this respect due to their ability to replicate nearly all of the properties of bulk quantum materials at the nanoscale and the relative ease in combining them with one another as well as incorporating them into new device architectures. Here, I will describe our recent studies combining 2D quantum materials and metasurfaces to achieve new and enhanced functionalities, including tunable THz transmission and Faraday rotation in graphene microribbon-based metasurfaces and control over exciton emission/dynamics in WSe2 monolayer/metasurface structures.
A pair of parallel metallic plates with nanometer-scale separations, or a ‘metallic nanotrench’, creates strongly enhanced electric field with uniform spatial distribution when a long wavelength radiation is incident. This property is not only useful for quantitative analysis of light-matter interactions, but also for potential electrochemical studies on nanoconfined molecules. Here, we show our progress on realizing sub-10 nm-wide metallic nanotrenches filled with various liquids to study interaction of nano-confined molecules with terahertz radiation. Large height-to-width aspect ratio and strong field enhancement of the nanotrenches enable sensitive detection of the nano-confined molecules, from which optical properties of the molecules can be determined. We demonstrate fabrication of the nanotrenches with widths as small as 2 nm, and study changes in their terahertz optical properties upon integration with various liquids. Also, we discuss anomalous optical properties of water molecules confined within sub-10 nm-wide metallic nanotrenches.
Atomic layer deposition is an efficient method for coating a few nanometer-thick alumina over a wafer scale. This method combined with the standard photolithography process was presented to fabricate metallic nanometer gaps that optically act in terahertz regimes. However, the cross-sectional view of the gap shape of the metal–insulator–metal nanogap structure varies depending on the conditions from the stepwise procedure. In specific, selecting photoresist materials, adding ion milling and chemical etching processes, and varying metal thicknesses and substrates result in various optical gap widths and shapes. Since the cross-sectional gap shape affects the field enhancement of the funneled electromagnetic waves via the nanogap, the control of tailoring the gap shape is necessary. Thus, we present five different versions of fabricating quadrangle-ring-shaped nanometer gap arrays with varying different kinds of outcomes. We foresee the usage of the suggested category for specific applications.
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