Controlled Nanoscale Cracking of Graphene Ribbons by Polymer Shrinkage

Controlled cracking of two-dimensional layered materials (2DLMs) can dramatically alter their crystallographic orientation, energy band gap, sheet resistance, and phonon softening. Previously, graphene has been ruptured using a variety of methods such as substrate-mediated deformation or using nanoscale probes. However, large-area, tunable nanoscale cracking in dry, suspended, and micropatterned graphene has yet to be demonstrated. Here, we describe a method to crack photolithographically patterned ribbons of graphene in a controlled manner. We first micropattern and suspend arrays of rectangular patterned graphene ribbons across the topographically patterned lines of SU8 and generate controlled cracks by tunable shrinkage of SU8 using electron beam irradiation. We utilize a statistical design of experiments (DOE) to identify that two variables, namely the extent of prior ultraviolet SU8 crosslinking and the irradiated electron beam dose, contribute most significantly to the nano to microscale breakage of micropatterned graphene ribbons. Also, the extent of nanoscale breakage in graphene can be tuned by varying the aforementioned factors. We anticipate that this approach can allow for integrated 2DLM-based electronic and optical devices with engineered defects or break junctions.