Orthogonal photopatterning of two-dimensional percolated network films for wafer-scale heterostructures

Molecular intercalation-based electrochemical exfoliation of two-dimensional (2D) materials can be used to create van der Waals heterostructures. However, the scalable assembly of vertical heterostructures typically requires the use of various chemical solvents for photolithography and subsequent transfer, which can leave behind chemical residues and limit the patterning resolution. We show that patterned van der Waals heterostructures can be fabricated from electrochemically exfoliated 2D flakes using a photoreactive crosslinker. When a 2D van der Waals percolated network with the crosslinker is exposed to ultraviolet light, the network junctions form covalent bonds, thereby enabling improved charge transport and orthogonal patterning of vertically stacked van der Waals thin-film networks without affecting the underlying prepatterned layers. Our approach can be used to create wafer-scale arrays of photopatterned field-effect transistors based on different 2D materials. The field-effect transistors exhibit high spatial uniformity and can be used to create logic gates, namely NOT, NAND and NOR gates. A photoreactive crosslinker can be used to directly pattern thin films of exfoliated two-dimensional flakes, and the technique can be performed sequentially to create patterned van der Waals heterostructures at wafer scales.