The researchers from Purdue University patterned a graphene film experimentally using a strong and short laser shock impact, which was generated by confined laser ablation of an ablative layer. A Q-switched Nd:YAG laser with a pulse width of ~7 ns was used. The pressure is controlled by the laser intensity.

Arrays of holes with diameters of 50, 100 and 200 nm were successfully patterned on monolayer graphene films. It was found that the pressure to punch a nanohole (50–200 nm) is only about 1.2–2.5 GPa, although the tensile strength of graphene is about 150 GPa.

Impact model

The team also carried out molecular dynamics (MD) simulations to study the dynamic punching process of graphene. Researchers from Arizona State University used MD to simulate the process of nanopatterning. Round holes with diameters of 100 and 50 nm were first simulated and the results found to be comparable to the experiments.

Graphene patterned with smaller diameters, which is difficult to perform experimentally, were also simulated, including theoretical predictions of the critical breaking pressure and force. The mechanical properties of graphene can then be analysed based on the simulations. This work should be a good supplement to the studies on the mechanical properties of graphene.

Full details including movies of the punching process can be found in the journal Nanotechnology.