Evolution of graphene lattice fracture at different indentation depths. This group of figures shows the process from the state at which the indentation depth reaches the critical depth to the state the graphene film is totally ruptured with an indenter radius of 2 nm, loading speed of 0.20 Å/ps, and aspect ratio of 1.2. (a) At critical moment: indentation depth 55.95 Å, load 655.08 nN; (b) first broken bond emerged: indentation depth 55.97 Å, load 635.60 nN; (c) pentagonal-heptagonal (5–7) and trilateral structures emerged: indentation depth 55.99 Å, load 426.04 nN; (d) three 5–7 structures: indentation depth 56.01 Å, load 310.45 nN; (e) single-chain structure emerged: indentation depth 56.51 Å, load 112.03 nN; (f) fracture of the chain: indentation depth 56.61 Å, load 93.70 nN.
Wang et al. Nanoscale Research Letters 2014 9:41 doi:10.1186/1556-276X-9-41