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

The electronic and optical properties of two-dimensionaltransitionmetal dichalcogenides can be tuned by a doping strategy. Herein, spiraland monolayer Er-doped WS2 (WE) flakes have been synthesizedby chemical vapor deposition using ErCl3, WO3, and S as precursors. The growth and properties of WE flakes havebeen systematically studied based on experimental and theoreticalanalysis. The morphology, size, and thickness of WE flakes can beregulated 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 flakesduring the growth but also drives the formation of screw dislocationsowing to the internal strain in the lattice induced by Er3+ doping. The WE flakes exhibit near-infrared (NIR) emission at & SIM;1530nm under 980 nm excitation, which corresponds to the energy transitionfrom (4) I (13/2) to (4) I (15/2) of the Er3+ dopants.In addition, the WE-based device exhibits improved NIR photoresponsewith a 16.9-fold enhancement in photocurrent compared with that ofthe WS2-based device. Our work provides a simple methodfor the preparation of highly crystalline WE flakes with NIR emissionand enhanced NIR photoresponse.