Elastic straining of free-standing monolayer graphene

Ke Cao,Yang Lu,Ying Han,Zhiping Xu,Thuc Hue Ly,Shizhe Feng,Libo Gao

doi:10.1038/s41467-019-14130-0

Abstract

The sp2 nature of graphene endows the hexagonal lattice with very high theoretical stiffness, strength and resilience, all well-documented. However, the ultimate stretchability of graphene has not yet been demonstrated due to the difficulties in experimental design. Here, directly performing in situ tensile tests in a scanning electron microscope after developing a protocol for sample transfer, shaping and straining, we report the elastic properties and stretchability of free-standing single-crystalline monolayer graphene grown by chemical vapor deposition. The measured Young’s modulus is close to 1 TPa, aligning well with the theoretical value, while the representative engineering tensile strength reaches ~50-60 GPa with sample-wide elastic strain up to ~6%. Our findings demonstrate that single-crystalline monolayer graphene can indeed display near ideal mechanical performance, even in a large area with edge defects, as well as resilience and mechanical robustness that allows for flexible electronics and mechatronics applications.

Highlights

The sp[2] nature of graphene endows the hexagonal lattice with very high theoretical stiffness, strength and resilience, all well-documented
We circumvent the gripping problem by developing well-controlled sample transfer and shaping techniques, namely well control of the shape of free-standing chemical vapor deposition (CVD)-grown graphene samples, which were transferred onto the tensile straining stage through a modified wet-transfer method, and explore the in-plane mechanical responses of suspended monolayer graphene by our previously developed in situ nanomechanical testing platform under SEM37. We demonstrate their representative engineering tensile strength reaching ~50–60 GPa with sample-wide elastic strain up to ~6%, even in a large area with edge defects, displaying near-ideal mechanical performance, high resilience, and mechanical robustness
The crystalline structure of graphene ribbons suspended on the gap was further characterized by transmission electron microscope (TEM) multi-point diffraction analysis

Summary

Introduction

The sp[2] nature of graphene endows the hexagonal lattice with very high theoretical stiffness, strength and resilience, all well-documented. Directly performing in situ tensile tests in a scanning electron microscope after developing a protocol for sample transfer, shaping and straining, we report the elastic properties and stretchability of free-standing single-crystalline monolayer graphene grown by chemical vapor deposition. In the experimental studies reported in literature, the stretchability of finite graphene sheets was limited by the presence of point and line defects, resulting in a common tensile strain to failure of ~1%7,36, far below the strain level associated with notable strain effects These facts clearly indicate that a samplewide elastic strain level much higher than 1% is desired to endow graphene with realistic strain-tunable device applications[27]

Methods

Results

Conclusion