Defect-Free Mechanical Graphene Transfer Using Doping Adhesive Gel Buffer.

The synthesis of uniform low-defect graphene on a catalytic metal substrate is getting closer to the industrial level. However, its practical application is still challenging due to the lack of an appropriate method for its scalable damage-free transfer to a device substrate. Here, an efficient approach for a defect-free, etchant-free, wrinkle-free, and large-area graphene transfer is demonstrated by exploiting a multifunctional viscoelastic polymer gel as a simultaneous shock-free adhesive and dopant layer. Initially, an amine-rich polymer solution in its liquid form allows for conformal coating on a graphene layer grown on a Cu substrate. The subsequent thermally cured soft gel enables the shock-free and wrinkle-free direct mechanical exfoliation of graphene from a substrate due to its strong charge-transfer interaction with graphene and excellent shock absorption. The adhesive gel with a high optical transparency works as an electron doping layer toward graphene, which exhibits significantly reduced sheet resistances without optical transmittance loss. Lastly, the transferred graphene layer shows high mechanical and chemical stabilities under the repeated bending test and exposure to various solvents. This gel-assisted mechanical transfer method can be a solution to connect the missing part between large-scale graphene synthesis and next-generation electronics and optoelectronic applications.