Transfer-induced wrinkles are universal issues when transferring transition metal dichalcogenide (TMDC) monolayer from an as-grown substrate to a target substrate. The undesired transfer-induced wrinkles can mainly be attributed to wettability, which refers to the ability of a liquid to come in contact with a solid surface. Herein, an adjustable wettability-assisted transfer (AWAT) method with different mixtures of transfer media to reduce the density of wrinkles is developed. By manipulating the wettability of the transfer medium with different ratios of alcohol and de-ionized (DI) water, the TMDC monolayer is smoothly attached to the target substrate, thus achieving a wrinkle-less transferred TMDC monolayer. With this method, the density of wrinkles can be decreased by ≈15-20% compared with the conventional transfer method by pure DI water. The transferred MoS 2 monolayer with the AWAT method can achieve enhanced carrier mobility from ≈20 to ≈35 cm 2 V −1 s −1 in average, which is 30 times larger than that transferred by pure DI water. The AWAT method applied to a WS 2 monolayer onto a SiO 2 /p + -Si substrate and a MoS 2 monolayer onto a HfO 2 /p + -Si substrate are demonstrated, which is beneficial in research and applications involving the transfer of TMDC monolayer.

We report a top-down method for high-yield production of Janus monolayer MoSSe. In particular, we replace the top S atom with Se by controlled plasma-assisted selenization of monolayer MoS2. Based on the Raman Spectroscopy results, all of the characterized monolayer MoS2 triangles are completely transformed to Janus MoSSe. The Janus structure of MoSSe is confirmed directly by means of high-resolution transmission electron microscopy (TEM) and energy-dependent X-ray photoelectron spectroscopy (XPS). Density Functional Theory (DFT) calculations are performed to determine the effect of the Se-concentration on the electronic properties of Janus MoSSe. Our method provides an avenue towards high-yield production and full exploration of Janus Transition Metal Dichalcogenides (TMDs).

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