Quantifying the local mechanical properties of twisted double bilayer graphene

TL;DR

This study uses Ultrasonic Force Microscopy to measure local mechanical properties of twisted double bilayer graphene, revealing significant tunability of Young's modulus at domain walls, which is confirmed by models and important for nanomechanical device design.

Contribution

First direct nanomechanical measurement of twisted double bilayer graphene's local Young's modulus variation using UFM, demonstrating tunability at domain walls.

Findings

Young's modulus softens by 7-17% at domain walls

UFM measurements are validated by force-field models

Nanomechanical properties are highly tunable in twisted 2D materials

Abstract

Nanomechanical measurements of minimally twisted van der Waals materials remained elusive despite their fundamental importance for device realisation. Here, we use Ultrasonic Force Microscopy (UFM) to locally quantify the variation of out-of-plane Young's modulus in minimally twisted double bilayer graphene (TDBG). We reveal a softening of the Young's modulus by 7\% and 17\% along single and double domain walls, respectively. Our experimental results are confirmed by force-field relaxation models. This study highlights the strong tunability of nanomechanical properties in engineered twisted materials, and paves the way for future applications of designer 2D nanomechanical systems.