Homogeneous heterophase junction based on cubic/orthomorphic SnS for chemiresistive room temperature trace-ethanol sensor

Herein, we developed a homogeneous heterophase structure based on the stereochemically-active cubic/orthorhombic SnS (CUB/ORT-SnS) by chemical precipitation and vacuum annealing. By precisely adjusting the annealing temperature, spherical cubic-SnS partially transformed into block-like orthorhombic phase. In the constructed heterophase structure, abundant junction interfaces which directly exposed in the atmosphere, serve as high-active adsorption centers, effectively hoisting the ethanol adsorption capability of SnS. The experimental results show that CUB/ORT-SnS sensor exhibits a response of 184% towards 5 ppm ethanol with rapid response-recovery process at room temperature (RT). Moreover, in order to improve the selectivity of the sensor to ethanol vapor, principal component analysis (PCA) was adopted to realize the specific identification towards ethanol and isopropanol. Further investigations based on DFT calculations and band alignment indicate that local cubic phase SnS of the heterophase structure is the strong electron trap, and forms effective conductive path with ethanol molecules. Benefiting from the enrichment of the interface adsorption sites and the enhancement of carrier transport and diffusion, the heterophase junction of SnS obtains remarkably boosted ethanol-sensing performance. This work constructs a homogeneous heterophase structure for sensing ethanol at RT, which provides a new design strategy for developing high-performance VOCs gas sensors.