No Tilt Angle Dependence of Grain Boundary on Mechanical Strength of Chemically Deposited Graphene Film

Abstract

Although graphene has been successfully grown in large scale via chemical vapor deposition (CVD), it is still questionable whether the mechanical properties of CVD graphene are equivalent to those of exfoliated graphene. In addition, there has been an issue regarding how the tilt angle of the grain boundary (GB) affects the strength of graphene. We investigate the mechanical properties of CVD graphene with nanoindentation from atomic force microscopy and transmission electron microscopy. Surprisingly, the samples with GB angles of 10 degrees and 26 degrees yielded similar fracture stresses of similar to 80 and similar to 79 GPa, respectively. Even for samples with GB exhibiting a wider range, from 0 degrees to 30 degrees, only a slightly wider fracture stress range (similar to 50 to similar to 90 GPa) was measured, regardless of tilt angle. The results are contrary to previous studies that have reported that GBs with a larger tilt angle yield stronger graphene film. Such a lack of angle dependence of GB can be attributed to irregular and well-stitched GB structures.