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- Chemistry; Materials Science
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Functionalization of transition metal dichalcogenides has been studied with the aim of tuning their electrical and optical properties, but structural information during functionalization and its reversibility have not been elucidated. We report a simple and effective method for hydrogenation of monolayer MoSeusing hydrogen plasma treatment. The covalent bonding of hydrogen to MoSewas confirmed by X-ray photoelectron spectroscopy, and the degree of hydrogenation was modulated from 32% to 80% by increasing the plasma treatment time from 5 to 40 s. Transmission electron microscopy confirmed a 1.5% reduction in the lattice constant of hydrogenated MoSewithout structural damages or defects; crystal structures of hydrogenated MoSeand as-prepared MoSewere identical. Photoluminescence (PL) investigation of hydrogenated MoSeshowed charge transfer from hydrogen to MoSe. Furthermore, reversible desorption of hydrogen from hydrogenated MoSewas achieved by heat treatment. The optical and electrical properties of as-prepared and hydrogenated MoSesamples were compared. The PL peak of hydrogenated MoSereturned to the as-prepared one after heat treatment at 500 °C. Furthermore, the electron mobility of MoSedecreased from 29 to 9 cmVsafter hydrogenation and was restored to 27 cmVsupon heat treatment at 500 °C. This reversible hydrogen adsorption and desorption lends control over the optical and electrical properties of monolayer MoSeand contributes to the hydrogen functionalization of monolayer transition metal dichalcogenides and other two-dimensional materials.