Modified metal-assisted exfoliation for low disorder, large monolayer devices

Exfoliating two-dimensional(2D) materials down to monolayers is of great significance for fundamental exploration of emerging physical phenomenon because of their unique band structure and flexible control with electrostatic gate tuning. Mechanical exfoliation, which starts with the first isolation of graphene with scotch tape, provides high quality 2D material single crystals but usually suffers from insufficient monolayer yield and lateral size. Here, we report a facile modified metal-assisted mechanical exfoliation method to produce high quality 2D material monolayer arrays on bare Si chip without exposing to water or solution based etching process. The resulting transition metal dichalcogenide (TMD) monolayers can be assembled by standard dry transfer techniques into BN encapsulated devices with low disorder, which allows for further investigation of their intrinsic properties with tunable dual gates. This approach provides a simple and efficient way to produce high quality, dry transfer assembly compatible 2D material arrays with intrinsic properties, and thus accelerates potential fundamental research on properties and development of proof-of concept devices.