Fig. 3. Current challenges in the mass production of 2D materials.

a Single-crystal homo/heteroepitaxial growth, wrinkle formation by thermal expansion coefficient mismatch between 2D materials and growth substrates, and cracking/contamination during the transfer process are all issues presented by the CVD technique. b Inhomogeneous size and thickness of 2D nanosheets and poor production yield are problems associated with liquid exfoliation. c Low durability and instability of 2D materials by defects and environmental pollution remain challenges for wet chemical synthesis.