UC Berkeley

The development of room-temperature sensing devices for detecting small concentrations of molecular species is imperative for a wide range of low-power sensor applications. We demonstrate a room-temperature, highly sensitive, selective, stable, and reversible chemical sensor based on a monolayer of the transition-metal dichalcogenide Re_0.5Nb_0.5S₂. The sensing device exhibits a thickness-dependent carrier type, and upon exposure to NO₂ molecules, its electrical resistance considerably increases or decreases depending on the layer number. The sensor is selective to NO₂ with only minimal response to other gases such as NH₃, CH₂O, and CO₂. In the presence of humidity, not only are the sensing properties not deteriorated but also the monolayer sensor shows complete reversibility with fast recovery at room temperature. We present a theoretical analysis of the sensing platform and identify the atomically sensitive transduction mechanism.