Correlating Morphology and NO2 Gas Detection at Room Temperature in Layered Tin Diselenide

Two-dimensional layered tin diselenide (SnSe2) is a promising material for NO2 gas detection at room temperature because of its high adsorption energy of NO2 and a good intrinsic conductivity. However, there are only a few reports on dependence on its morphology and NO2 gas detection properties. Here, we investigate the correlation with the morphologies and NO2 gas detection properties of SnSe2 synthesized by a hydrothermal route. With increasing the reaction time, the morphologies of SnSe2 are changed from disk-like shape to flower-like hierarchical one caused by the inherent self-assembly behavior, while preserving the hexagonal crystal structure. Based on various morphologies of SnSe2, we fabricated gas sensor devices with interdigitated electrodes. Among various morphologies of SnSe2, the hierarchical SnSe2 device exhibits the highest NO2 gas detection properties at room temperature, achieving gas response of 22% toward 100 ppm NO2 and superior gas selectivity with respect to other gas species. This is attributed to the higher specific surface area of hierarchical morphology than other morphologies and improved crystallinity.