Towards bubble-free, centimeter-sized bilayer graphene enabled by backside lamination

Abstract

Van der Waals (vdW) homo-/heterostructures stacked by atomically thin two-dimensional materials have received much attention due to their unique physical properties and outstanding device performance. However, the bubbles at the interface of vdW homo-/heterostructures commonly exert undesirable effects that would deteriorate material quality and thus limit the size and design of the device. Herein, we propose a novel backside lamination method, by which bubble-free, centimeter-sized bilayer chemical-vapor-deposited (CVD) graphene films can be well fabricated. The key factor in our method is that the backsides, adjacent to the metal growth substrate, of two graphene layers can be directly dry-laminated by designing asymmetric transfer media. The as-transferred bubble-free bilayer graphene exhibits exceptional film characteristics, including an ultra-flat surface, clear moiré patterns, uniform interlayer coupling, and negligible strain fluctuation. Additionally, twisted bilayer graphene exhibiting uniform twisted angles with only ∼5% deviation can also be prepared. Overall, our method demonstrates great potential for achieving vdW homo-/heterostructures with bubble-free interfaces and uniform film features.