  Growth of two-dimensional van der Waals layered single-crystal (SC) films is
highly desired to manifest intrinsic material sciences and unprecedented
devices for industrial applications. While wafer-scale SC hexagonal boron
nitride film has been successfully grown, an ideal growth platform for diatomic
transition metal dichalcogenide (TMdC) film has not been established to date.
Here, we report the SC growth of TMdC monolayers in a centimeter scale via
atomic sawtooth gold surface as a universal growth template. Atomic
tooth-gullet surface is constructed by the one-step solidification of liquid
gold, evidenced by transmission-electron-microscopy. Anisotropic adsorption
energy of TMdC cluster, confirmed by density-functional calculations, prevails
at the periodic atomic-step edge to yield unidirectional epitaxial growth of
triangular TMdC grains, eventually forming the SC film, regardless of Miller
indices. Growth using atomic sawtooth gold surface as a universal growth
template is demonstrated for several TMdC monolayer films, including WS2, WSe2,
MoS2, MoSe2/WSe2 heterostructure, and W1-xMoxS2 alloy. Our strategy provides a
general avenue for the SC growth of diatomic van der Waals heterostructures in
a wafer scale, to further facilitate the applications of TMdCs in post silicon
technology.
