Plasma Treatment for Achieving Oxygen Substitution in Layered MoS₂ and the Room-Temperature Mid-Infrared (10 μm)...

Highly sensitive photodetectors in the mid-infrared (MIR, 3-15 μm) are highly desired in a growing number of applications. However, only a handful of narrow-band-gap semiconductors are suitable for this purpose, most of which require cryogenic cooling to increase the signal-to-noise ratio. The realization of high-performance MIR photodetectors operating at room temperature remains a challenge. Herein, we report on plasma-treated few-layer MoS₂ for room-temperature MIR (10 μm) photodetection. Oxygen plasma treatment, which is a mature microfabrication process, is employed. The ion kinetic energy of oxygen plasma is adjusted to 70-130 eV. A photoresponsivity of 0.042 mA/W and a detectivity of 1.57 × 10⁷ Jones are obtained under MIR light (10 μm) illumination with an average power density of 114.6 mW/cm². The photoresponse is attributed to the introduction of electronic states in the band gap of MoS₂ through oxygen substitution. A graphene/plasma-treated MoS₂/graphene device is further demonstrated to shorten the active channel while maintaining the illumination area. The photoresponsivity and detectivity are largely boosted to 1.8 A/W and 2.64 × 10⁹ Jones, respectively. The excellent detective performance of the graphene/plasma-treated MoS₂/graphene device is further demonstrated in single-detector MIR (10 μm) scanning imaging. This work offers a facile approach to constructing integrated MoS₂-based MIR photodetectors.