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Previously, 2D ReS2 has only been prepared by mechanical exfoliation from bulk crystal which was synthesized via chemical vapor transport at high temperature (> 1000 C) for several weeks.[16] Most recently, two groups have reported the synthesis of ReS2 by using chemical vapor deposition (CVD) growth method, where ammonium perrhenate (NH4ReO4) and Re powder were used as Re source, respectively.[17, 18] Though great efforts have been made to prepare 2D ReS2, controllable synthesis of ReS2 with high-crystal-quality and uniform thickness still faces great challenge. For example, using NH4ReO4 as Re source, which has high valence state Re (+ 7), to grow ReS2 may suffer from low crystal quality due to lots of by-product.[18] Directly using Re powder as Re source can avoid this problem, but the high-melting point of Re (3180 C) always lead to the low yield of ReS2 because the low vapor pressure of Re inevitably restricts the vapor pressure of ReS2 in the CVD system. Besides, the distorted 1T structure and the weaker interlayer coupling of ReS2 make it preferable to grow into dendritic structure and thick flake on amorphous SiO2 substrate.[17, 18] These limitations pose great difficulty to the preparation of ReS2, and thus restrict its application. In this work, we demonstrate a tellurium-assisted CVD method to synthesize high quality monolayer ReS2 in largescale on mica substrate (Figure 1a, b). The idea is based on the Re–Te binary eutectic, whose eutectic point can be lowered down to 850 C, even to 430 C when Te–Re weight ratio is up to 90%(Figure S1, Supporting Information).[19] Hence, introducing Te powder into Re …