Chemical Vapor Deposition of Er-Doped WS2 Flakes with Near-Infrared Emission and Enhanced Near-Infrared Photoresponse

The electronic and optical properties of two-dimensional transition metal dichalcogenides can be tuned by a doping strategy. Herein, spiral and monolayer Er-doped WS2 (WE) flakes have been synthesized by chemical vapor deposition using ErCl3, WO3, and S as precursors. The growth and properties of WE flakes have been systematically studied based on experimental and theoretical analysis. The morphology, size, and thickness of WE flakes can be regulated by adjusting the molar ratio of ErCl3/WO3 and the growth time. It has been found that the ErCl3 precursor not only acts as the promoter of the WE flakes during the growth but also drives the formation of screw dislocations owing to the internal strain in the lattice induced by Er3+ doping. The WE flakes exhibit near-infrared (NIR) emission at ∼1530 nm under 980 nm excitation, which corresponds to the energy transition from 4I13/2 to 4I15/2 of the Er3+ dopants. In addition, the WE-based device exhibits improved NIR photoresponse with a 16.9-fold enhancement in photocurrent compared with that of the WS2-based device. Our work provides a simple method for the preparation of highly crystalline WE flakes with NIR emission and enhanced NIR photoresponse.