CVD Growth and Dry Transfer of Large High Quality Graphene Crystals

Graphene and other 2D materials revealed electronic properties that are fundamentally different from those in their bulk counterparts, and they carry the promise of novel device applications. Thus far, the best quality 2D layers are prepared by mechanical exfoliation, but this labor-intensive method does not lend itself to large-scale production. Alternatively, chemical vapor deposition (CVD) can be used to consistently produce large samples, but in this case, the substrate surface roughness limits the maximum size of single crystals and introduces grain boundaries, which degrade the carrier mobility. For CVD production of graphene, the substrate of choice is copper. We describe a method of electrochemical polishing (ECP) of copper which results in larger crystals. By optimizing the voltage range and chemical composition of the etchant, we achieved single-crystal domains that are significantly larger than those attained by mechanical exfoliation. The crystals are then transferred from the copper substrate to boron nitride using the dry-transfer method [1]. We show that by using ECP, CVD, and dry transfer, it is possible to consistently and reliably obtain large, high-quality graphene samples.

1. L. Banszerus et al. Sci. Adv. 1, e1500222 (2015).