Two-dimensional (2D) materials and

Two-dimensional (2D) materials and their programmable heterostructures have attracted much more attentions attention due to their vagaries of physical properties. The 2D materials of single component in these heterostructures can be graphene, hBN1, transition metal chalcogenides (TMCs, including dichalcogenides and monochalcogenides), transition metal halides (TMHs), black phosphorus2, and other kinds of materials. Among the studied 2D materials, TMCs and TMHs have abundant properties, such as semiconducting, superconducting, ferromagnetic, ferroelectric, electrocatalytic etc.. Similar to graphene, most TMCs and TMHs can also be prepared by either bottom-up or top-down routes. Under the premise of retaining their intrinsic physical properties, micromechanical exfoliation of bulk layered materials3, 4, 5, 6, molecular beam epitaxy (MBE) and chemical vapour deposition (CVD) growth are main methods until now. Although many TMCs, like MoS2, NbSe2, etc., can be prepared by above methods, most of these atomically thin TMCs are fragile and easily affected after exposure to atmospheric environment with H2O or O2, leading to remarkable changes in their physical or chemical properties.7, 8 This structural degradation of TMCs significantly hinders their further structural characterization and performance measurements, and their environmental instability has already increased the difficulty of stacking vertical heterostructures.9, 10