Top-down Production of 2D Materials in Macroscopic Sizes

Scalable and controllable top-down exfoliation processes to obtain 2D materials with sufficient size and high quality are often desired for their mass production and device implementation. We have developed a few metal-assisted methods to exfoliate a variety of van der Waals (vdW) single crystals into 2D flakes with controlled thickness and morphology, and achieved high yield, high quality, and macroscopic dimensions. Examples include single-crystal monolayer transition metal dichalcogenides (TMDCs), few-layer hBN flakes with controlled thickness, and monolayer nanoribbons. The universal top-down approach will gain access to a variety of 2D nanoribbons, analogous to the widely used Scotch tape exfoliation in preparation of monolayers. High-quality and large-area monolayers will allow us to further assemble them into artificial stacks, which has been shown to achieve enhanced responses in high-harmonic generation. The heterobilayer stacks have been used to reveal light-induced interlayer thermal transfer dynamics in ultrafast electron diffraction experiments. Obtaining macroscopic 2D materials with enhanced yield will not only facilitate the fundemental research, but also take us one step closer to mass production and commercialization of the 2D devices in the future.