“Preparation defines the future”. Ever since its discovery, the synthesis of graphene has for a long time played a significant role in the graphene community.
Scientists have realized the preparation of large-area graphene films by using transition metals such as Ni or Cu as substrate. Superior-quality large-scale continuous monolayer graphene has been successfully grown on Cu foils.
This cost-effective and simple method has been extensively accepted as the most promising way for graphene production in the industrial level. However, graphene films attained via this method are generally polycrystalline with domain boundaries, which would majorly destroy the optical, electrical, thermal and mechanical properties.
Thus, finding a method for synthesizing large-size single-crystal graphene is considered to be a huge scientific problem that needs to be solved.
Prof. K. H. Liu, Prof. D. P. Yu and Prof. E. G. Wang from Peking University teaming up with Prof. F. Ding from Ulsan National Institute of Science and Technology and other collaborators discovered a new way to prepare 5×50 cm2 single-crystal graphene on industrial Cu foils (Science Bulletin 2017, 62, 1074). First, they converted industrial polycrystalline Cu foils into single-crystal Cu(111) by thermal annealing with the help of a temperature-gradient-driving technique. Graphene domains were epitaxially grown on the Cu(111) substrate and then seamlessly combined together to produce large single-crystal graphene films.
The graphene growth rate and each individual graphene domain size were obviously improved as a result of being combined with their ultrafast graphene growth technique (Nature Nanotechnology 2016, 11, 930). Additionally, oxygen discharged from oxide at high temperature was demonstrated to further enhance the domain alignment, which would majorly improve the quality of graphene films.
This reported technique permits the synthesis of large-size single-crystal graphene films, which comprise of superior properties for different high-end applications, particularly in electronics, such as the transparent film replacing ITO and large-scale fabrication of THz devices. This technique will also enable the epitaxial growth of several other 2D single-crystal materials on graphene with meter-sized dimension.