SnSe 2 is an anisotropic binary-layered material with rich physics, which could see it used for a variety of potential applications. Here, we investigate the gas-sensing properties of SnSe 2 using first-principles calculations and verify predictions using a gas sensor made of few-layer SnSe 2 grown by chemical vapor deposition. Theoretical simulations indicate that electrons transfer from SnSe 2 to NO 2 , whereas the direction of charge transfer is the opposite for NH 3 . Notably, a flat molecular band appears around the Fermi energy after NO 2 adsorption and the induced molecular band is close to the conduction band minimum. Moreover, compared with NH 3 , NO 2 molecules adsorbed on SnSe 2 have a lower adsorption energy and a higher charge transfer value. The dynamicsensing responses of SnSe 2 sensors confirm the theoretical predictions. The good match between the theoretical prediction and experimental demonstration suggests that the underlying sensing mechanism is related to the charge transfer and induced flat band. Our results provide a guideline for designing high-performance gas sensors based on SnSe 2 . KEYWORDS: SnSe 2 , gas sensing, charge transfer, first-principles calculations, selective gas sensing, NO 2 gas sensor, NH 3 gas sensor
Air pollution is a global problem, which poses serious environmental concerns and health risks. In light of this, a key aspect of the challenge of managing air pollution is effective monitoring, which requires reliable high‐sensitivity sensors with strong selectivity and long‐term stability. Layered materials represent an emergent class of materials with extraordinary electronic properties and physicochemical properties, and, therefore, are a highly attractive prospect for this field. Here, such a sensor for NO2 based on GaSe is presented. An ultrahigh sensitivity of 0.5 part per billion (p.p.b.) is achieved at room temperature, and the NO2 selectivity ratios with respect to other likely interfering environmental gases are larger than 100. Moreover, no great degradation is observed after 10 days of air exposure. As a practical demonstration, the GaSe‐based sensors are also used to detect vehicle exhaust emission, and wearable GaSe‐based NO2 sensors are presented and tested. Based on the results obtained in this work, it is believed that GaSe‐based sensors can be used for the detection of NO2 in real‐world applications.
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