Anisotropic monolayer of ReX2 on Au foils for exploring abnormal growth behavior and electronic properties

As an emerging class of semiconducting transition metal dichalcogenides (TMDCs), two-dimensional (2D) rhenium dichalcogenides (ReX 2 , X = S or Se) have recently aroused great research interest due to their unique anisotropic structure (1T’ phase), and the related novel properties and applications. Recently, many efforts have been devoted to the controllable syntheses of high-quality monolayer or few-layer ReX 2 flakes/films by chemical vapor deposition (CVD), wherein the metallic Au foil is found to be a unique substrate, due to the relatively strong interfacial coupling between monolayer ReX 2 and Au. And the conductive nature of Au enables in situ characterizations of the as-grown ReX 2 samples, which is essential for exploring the fundamental properties and internal growth mechanisms. Hereby, this review focuses on the recent progresses on the CVD syntheses and in situ characterizations of high-quality monolayer ReX 2 flakes/films and their heterostructures with graphene on Au foils. The effects of Au foils on improving the crystal quality and inducing the growth of monolayer ReX 2 single crystals are intensively addressed. The crystallinity, domain morphology, atomic and electronic structures, as well as the growth behaviors of monolayer ReX 2 flakes/films and graphene/ReX 2 heterostructures on Au revealed by in situ characterization techniques are also highlighted. As contrasts, the growth behaviors of monolayer or few-layer ReX 2 on insulating substrates are also discussed. Besides, the potential applications of 2D ReX 2 in new-generation electronic, optoelectronic devices, and energy-related fields are also introduced. Finally, future research directions are also prospected for propelling the practical applications of 2D ReX 2 materials in more versatile fields.