From Auto-Kirigamito Drumheads: Suspended, Self-Tearing,and Strained Graphene Nanostructures Formed by Nanoindentation

Nanoindentation of substrate-supported graphene can produce auto-kirigami (AK) structures: spontaneously folded and extended self-tearing nanoribbons up to several micrometers in length. However, the mechanisms governing their formation and yield are poorly understood. Here, we study graphene AK through statistical analysis of high-throughput experiments involving hundreds-fold arrays of indents on highly uniform regions of exfoliated monolayer and bilayer graphene, with no applied oscillation (in contrast with prior work). Post-mortem atomic force microscopy analysis reveals a baseline AK formation rate of 13–61% for monolayers and 0–17% for bilayers depending on inter-indent pitch. Force–distance curves of each type of nanostructure showed no appreciable differences. Moreover, graphene can remain intact after indentation, permitting formation of unbroken graphene suspended over or conformed within indents. Inter-indent pitch affects the absolute and relative formation rates of these nanostructures, attributed to indentation-induced tensile graphene strain. This advances the understanding of mechanisms for controlled formation of nanostructures, including twisted bilayers of graphene and other van der Waals materials.