2D/2D SnS2/SnSe2 van der Waals heterostructure for highly sensitive room-temperature NO2 sensor: Key role of interface contact

Abstract

2D/2D van der Waals (vdW) heterostructure is an effective strategy for improving the functions of 2D layered nanomaterials due to the high-quality heterointerfaces with the lacked dangling bonds at the interfaces. However, little attention was paid to investigating the effect of heterointerface amount and quality on gas-sensing performance. Here, two sets of 2D/2D SnS2/SnSe2 vdW heterostructures with tunable SnSe2 content are fabricated by physical mixing and solvothermal growth methods for room-temperature NO2 gas sensors. Compared to pure SnS2 and SnSe2 layers, the creation of 2D/2D vdW heterostructure shows a great improvement in sensing performance at room temperature. Moreover, the response and sensitivity are further enhanced by increasing the amount of heterointerface. More importantly, the SSSe-1.0 vdW heterostructures with improved interface contact by solvothermal growth exhibit a much higher response and sensitivity than that of MSSe-1.4 prepared by physical mixing, showing the highest response (1274.1% for 2 ppm) with the sensitivity of 598.2 % ppm−1 to NO2 gas. The mechanism of enhanced response and sensitivity for the SSSe-1.0 sensor is investigated by DFT calculation and XPS analysis, revealing that the strengthening of the interface contact improves the charge transfer and NO2 adsorption in 2D/2D SnS2/SnSe2 vdW heterostructure. Such effect of heterojunction number and interface contact on sensing performance paves a solid step toward the development of 2D layered crystals-based NO2 sensors and extends to applications in other fields.