Taylor, Hayden1; Nguyen, Vu1; Gramling, Hannah1; Towle, Clarissa1; Li, Wan1; Lien, Der-Hsien1; Kim, Hyungjin1; Chrzan, Daryl1; Javey, Ali1; Xu, Ke1; Ager, Joel1
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One of the major challenges in the van der Waals (vdW) integration of 2D materials is achieving high-yield and high-throughput assembly of pre-defined sequences of monolayers into heterostructure arrays. Mechanical exfoliation has recently been studied as a promising technique to transfer monolayers from a multilayer source synthesized by other techniques, allowing the deposition of a wide variety of 2D materials without exposing the target substrate to harsh synthesis conditions. Although a variety of processes have been developed to exfoliate the 2D materials mechanically from the source and place them deterministically onto a target substrate, they can typically transfer only either a wafer-scale blanket or one small flake at a time with uncontrolled size and shape. Here we present a method to assemble arrays of lithographically defined monolayer WS2 and MoS2 features from multilayer sources and directly transfer them in a deterministic manner onto target substrates. This exfoliate–align–release process—without the need of an intermediate carrier substrate—is enabled by combining a patterned, gold-mediated exfoliation technique with a new optically transparent, heat-releasable adhesive. WS2/MoS2 vdW heterostructure arrays produced by this method show the expected interlayer exciton between the monolayers. Light-emitting devices using WS2 monolayers were also demonstrated, proving the functionality of the fabricated materials. Our work demonstrates a significant step towards developing mechanical exfoliation as a scalable dry transfer technique for the manufacturing of functional, atomically thin materials.
