The morphology of doubly-clamped graphene nanoribbons

Christian Brand,Jani Kotakoski,Markus Arndt,Yigal Lilach,Ori Cheshnovsky,Clemens Mangler,Mohammad R A Monazam

doi:10.1088/2053-1583/abe952

Abstract

Understanding the response of micro/nano-patterned graphene to mechanical forces is instrumental for applications such as advanced graphene origami and kirigami. Here, we analyze free-standing nanoribbons milled into single-layer graphene by focused ion beam processing. Using transmission electron microscopy, we show that the length L of the structures determines their morphology. Nanoribbons with L below 300 nm remain mainly flat, whereas longer ribbons exhibit uni-axial crumpling or spontaneous scrolling, a trend that is well reproduced by molecular dynamics simulations. We measure the strain of the ribbons as well as their crystallinity by recording nanometer-resolved convergent beam electron diffraction maps, and show that the beam tails of the focused ion beam cause significant amorphization of the structures adjacent to the cuts. The expansive or compressive strain in the structures remains below 4%. Our measurements provide experimental constraints for the stability of free-standing graphene structures with respect to their geometry, providing guidelines for future applications of patterned graphene.

Highlights

Transferring paper-work techniques such as origami and kirigami to graphene promises novel threedimensional structures with a high potential for innovations [1,2,3,4]
Studying free-standing graphene nanoribbons written by Ga-ion-beam milling, we show that their morphology can be effectively manipulated by choosing the appropriate geometry
The results indicate that changes in the edge morphology lead to compressive strain in the ribbon, resulting in uni-axial crumpling

Summary

Introduction

Transferring paper-work techniques such as origami and kirigami to graphene promises novel threedimensional structures with a high potential for innovations [1,2,3,4]. These can be used to reduce the thermal conductivity [5], steer folding by dopants [6], and exploit tension for advanced kirigami patterns [7]. The prerequisites are the outstanding mechanical properties of graphene on the one hand and the influence of static ripples on the other hand, leading to a bending rigidity exceeding the expected value by three orders of magnitude [1]. Engineering the bending rigidity of single-layer graphene has remained challenging

Methods

Discussion

Conclusion