Optical Duality of Molybdenum Disulfide: Metal and Semiconductor.

Sakong, Wonkil; Gul, Hamza Zad; Ahn, Byungwook; Oh, Suar; Kim, Giheon; Sim, Eunji; Bahng, Jaeuk; Yi, Hojoon et al. · Nano Lett · 2022

basic_science · Level V

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Abstract

The two different light-matter interactions between visible and infrared light are not switchable because control mechanisms have not been elucidated so far, which restricts the effective spectral range in light-sensing devices. In this study, modulation of the effective spectral range is demonstrated using the metal-insulator transition of MoS<sub>2</sub>. Nondegenerate MoS<sub>2</sub> exhibits a photoconductive effect in detecting visible light. In contrast, degenerate MoS<sub>2</sub> responds only to mid-infrared (not visible) light by displaying a photoinduced heating effect via free carrier absorption. Depending on the doping level, the optical behavior of MoS<sub>2</sub> simulates the photoconductivity of either the semiconductor or the metal, further indicating that the optical metal-insulator transition is coherent with its electrical counterpart. The electrical switchability of MoS<sub>2</sub> enables the development of an unprecedented and novel design optical sensor that can detect both visible and mid-IR (wavelength of 9.6 μm) ranges with a singular optoelectronic device.