Direct laser patterning of two-dimensional lateral transition metal disulfide-oxide-disulfide heterostructures for ultrasensitive sensors

Two-dimensional (2D) heterostructures based on the combination of transition metal dichalcogenides (TMDs) and transition metal oxides (TMOs) have aroused growing attention due to their integrated merits of both components and multiple functionalities. However, nondestructive approaches of constructing TMD-TMO heterostructures are still very limited. Here, we develop a novel type of lateral TMD-TMO heterostructure (NbS₂-Nb₂O₅-NbS₂) using a simple lithography-free, direct laser-patterning technique. The perfect contact of an ultrathin TMO channel (Nb₂O₅) with two metallic TMDs (NbS₂) electrodes guarantee strong electrical signals in a two-terminal sensor. Distinct from sensing mechanisms in separate TMOs or TMDs, this sensor works based on the modulation of surface conduction of the ultrathin TMO (Nb₂O₅) channel through an adsorbed layer of water molecules. The sensor thus exhibits high selectivity and ultrahigh sensitivity for room-temperature detection of NH₃ (ΔR/R = 80% at 50 ppm), superior to the reported NH₃ sensors based on 2D materials, and a positive temperature coefficient of resistance as high as 15%-20%/°C. Bending-invariant performance and high reliability are also demonstrated in flexible versions of sensors. Our work provides a new strategy of lithography-free processing of novel TMD-TMO heterostructures towards high-performance sensors, showing great potential in the applications of future portable and wearable electronics.