Van der Waals epitaxial growth of two-dimensional non-layered CdS1-xSex for high-sensitivity NH3 detection

Two-dimensional (2D) materials are considered as ideal building blocks for constructing new functional gassensitive devices because of their large specific surface area, abundant active sites and high carrier mobility. However, research has mainly focused on 2D layered materials due to their easy availability. This work aims to further explore the application value of 2D non-layered materials in gas sensing. Firstly, van der Waals epitaxial growth of 2D non-layered CdS1-xSex on fluorophlogopite substrate was achieved by APCVD. Secondly, the CdS1-xSex-based gas sensor exhibits high sensitivity (626 % at 50 ppm NH3), low detection limit (1 ppm), fast response (12 s at 50 ppm NH3), good selectivity and repeatability to NH3 at room temperature. Notably, the sensing performance of the ternary CdS1-xSex for NH3 is better than other structures of binary CdS. This phenomenon is also further explained. Finally, density functional theory is used to calculate the adsorption energy and charge transfer properties, and the results reconfirm that CdS1-xSex is a promising NH3 sensing material. This work provides a universal synthesis method of 2D non-layered alloy materials, and explores the application of 2D CdS1-xSex in gas sensing for the first time, hoping to bring new ideas for the research of other 2D non-layered materials.