Controlled Layer Thinning and p‐Type Doping of WSe 2 by Vapor XeF 2

This report presents a simple and efficient method of layer thinning and p‐type doping of WSe 2 with vapor XeF 2 . With this approach, the surface roughness of thinned WSe 2 can be controlled to below 0.7 nm at an etched depth of 100 nm. By selecting appropriate vapor XeF 2 exposure times, 23‐layer and 109‐layer WSe 2 can be thinned down to monolayer and bilayer, respectively. In addition, the etching rate of WSe 2 exhibits a significant dependence on vapor XeF 2 exposure pressure and thus can be tuned easily for thinning or patterning applications. From Raman, photoluminescence, X‐ray photoelectron spectroscopy (XPS), and electrical characterization, a p‐doping effect of WSe 2 induced by vapor XeF 2 treatment is evident. Based on the surface composition analysis with XPS, the causes of the p‐doping effect can be attributed to the presence of substoichiometric WO x ( x < 3) overlayer, trapped reaction product of WF 6 , and nonstoichiometric WSe x ( x > 2). Furthermore, the p‐doping level can be controlled by varying XeF 2 exposure time. The thinning and p‐doping of WSe 2 with vapor XeF 2 have the advantages of easy scale‐up, high etching selectivity, excellent controllability, and compatibility with conventional complementary metal‐oxide‐semiconductor fabrication processes, which is promising for applications of building WSe 2 devices with versatile functionalities.