Abstract: Chemical vapor deposition (CVD) is an effective method for the growth of large scale two-dimensional materials. However, high density of vacancy defects are inevitably generated in the CVD process, which affects the photoelectric properties of the materials. In this work, millimeter-scale and atomic-thick WS₂ membranes were directly grown on p-type Si (111) substrates using an alkali metal halide-assisted CVD method. Er-doped WS₂ films (WS₂(Er)) were achieved by adding saturated ErCl₃ powders in the tungsten sources. Optical microscopy, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, photoluminescence and Raman spectroscopy techniques were used to characterize the materials systematically. The results show that the fluorescence intensity of WS₂(Er) films increase by an order of magnitude compared to pristine WS₂, and the central wavelength is significantly red-shifted. Fluorescence tests show that the fluorescence characteristics of WS₂ grown on Si substrates show a significant charge transfer effect compared to that of WS₂ on SiO₂ substrates. The photoelectric test results of WS₂ and WS₂(Er) field effect transistors based on SiO₂ substrate show that the optical responsiveness of WS₂(Er) field effect transistors is 4.015 A/W, and the external quantum efficiency is 784%, both of which are more than 2 000 times that of pristine WS₂ devices under the same conditions. This work has significance for research of rare earth doping in 2D materials.

Key words: CVD, WS₂, Er doping, single-crystal silicon, fluorescent property, photoelectric property