A collaboration between Flagship-affiliated physicists from RWTH Aachen University and Forschungszentrum Jülich, together with colleagues in Japan, devised a method for peeling graphene flakes from a CVD substrate with the help of intermolecular forces. It is an innovative variant on the traditional CVD process, which yields high quality material in a scalable manner, that might significantly narrow the performance gap between synthetic and natural graphene.
The process is heavily based on the strong van der Waals interaction that exists between graphene and hexagonal boron nitride, another 2D material within which it is encapsulated. Thanks to strong van der Waals interactions between graphene and boron nitride, CVD graphene can be separated from the copper and transferred to an arbitrary substrate. The process allows for re-use of the catalyst copper foil in further growth cycles, and minimizes contamination of the graphene due to processing.Raman spectroscopy and transport measurements on the graphene/boron nitride heterostructures reveal high electron mobilities comparable with those observed in similar assemblies based on exfoliated graphene. Furthermore, no noticeable performance changes are detected between devices developed in the first and subsequent growth cycles. This confirms the copper as a recyclable resource in the graphene fabrication process.
The researchers remark that until now, graphene synthesized by CVD has been significantly lower in quality than that obtained with the scotch-tape method, especially when it comes to the material’s electronic properties. But this new demonstrated method based on CVD yields ultra-high quality synthetic graphene samples. The process is in principle suitable for industrial-scale production, and narrows the gap between graphene research and its technological applications. The key is to transfer CVD graphene from its growth substrate in such a way that chemical contamination is avoided. The high mobility of pristine graphene is thus preserved, and the approach allows for the substrate material to be recycled without degradation.