Dry\nTransfer of van der Waals Junctions of Two-Dimensional\nMaterials onto Patterned Substrates Using Plasticized Poly(vinyl chloride)/Kamaboko-Shaped\nPolydimethylsiloxane

Two-dimensional (2D)\nmaterials can be transferred onto substrates\nwith various surface structures, opening up multiple functions and\napplications for 2D materials in the form of suspended membranes.\nIn this paper, we present a method for transferring exfoliated 2D\ncrystal flakes from SiO<sub>2</sub> substrates onto patterned substrates\nusing a poly(vinyl chloride) (PVC) layer mounted on a polydimethylsiloxane\n(PDMS) stamp structure. 2D crystal flakes can be transferred onto\nvarious patterned structures such as grooves, round holes, and periodic\nhole or groove patterns. Our method can also be used to fabricate\nsuspended van der Waals (vdW) heterostructures by assembling 2D crystal\nflakes on the PVC/PDMS stamp and then transferring them onto patterned\nsubstrates. The adhesiveness and curvature of the PVC/PDMS stamp were\ntuned, and a high successful transfer rate was realized due to the\nuse of kamaboko-shaped (semicylindrical) PDMS and the addition of\nan appropriate amount of a high-viscosity plasticizer to the PVC layer.\nTaking advantage of this method, we demonstrate the facile fabrication,\nsimply by transferring a vdW heterostructure onto an Au-coated groove\nsubstrate, of a suspended vdW field-effect transistor device with\nthe carrier density tuned using ionic gating. This method enables\nthe transfer of 2D crystal flakes and vdW heterostructures onto various\npatterned substrates, and hence it should help to advance suspended\n2D materials research.