Graphene-assisted metal transfer printing for wafer-scale integration of metal electrodes and two-dimensional materials

Metal–semiconductor junctions are essential components in electronic and optoelectronic devices. With two-dimensional semiconductors, conventional metal deposition via ion bombardment results in chemical disorder and Fermi-level pinning. Transfer printing techniques—in which metal electrodes are predeposited and transferred to create van der Waals junctions—have thus been developed, but the predeposition of metal electrodes creates chemical bonds on the substrate, which makes subsequent transfer difficult. Here we report a graphene-assisted metal transfer printing process that can be used to form van der Waals contacts between two-dimensional materials and three-dimensional metal electrodes. We show that arrays of metal electrodes with both weak (copper, silver and gold) and strong (platinum, titanium and nickel) adhesion strengths can be delaminated from a four-inch graphene wafer due to its weak van der Waals force and absence of dangling bonds, and transfer printed onto different substrates (graphene, molybdenum disulfide and silicon dioxide). We use this approach to create molybdenum disulfide field-effect transistors with different printed metal electrodes, allowing the Schottky barrier height to be tuned and ohmic and Schottky contacts to be formed. We also demonstrate the batch production of molybdenum disulfide transistor arrays with uniform electrical characteristics.