Observation of Pull-in Instability in Graphene Membranes under Interfacial Forces

TL;DR

This study experimentally measures the interfacial forces, mainly van der Waals, acting on graphene membranes near a post, revealing force dependence on distance and layer number, crucial for nanomechanical device design.

Contribution

The paper introduces a novel experimental method to quantify interfacial forces on atomically thin graphene membranes at nanometer separations.

Findings

Interfacial forces follow an inverse fourth power law with distance.

Force magnitude increases linearly with the number of graphene layers.

Method can be applied to other 2D materials for nanodevice development.

Abstract

We present a unique experimental configuration that allows us to determine the interfacial forces on nearly parallel plates made from the thinnest possible mechanical structures, single and few layer graphene membranes. Our approach consists of using a pressure difference across a graphene membrane to bring the membrane to within ~ 10-20 nm above a circular post covered with SiOx or Au until a critical point is reached whereby the membrane snaps into adhesive contact with the post. Continuous measurements of the deforming membrane with an AFM coupled with a theoretical model allow us to deduce the magnitude of the interfacial forces between graphene and SiOx and graphene and Au. The nature of the interfacial forces at ~ 10 - 20 nm separations is consistent with an inverse fourth power distance dependence, implying that the interfacial forces are dominated by van der Waals interactions. Furthermore, the strength of the interactions is found to increase linearly with the number of graphene layers. The experimental approach can be used to measure the strength of the interfacial forces for other atomically thin two-dimensional materials, and help guide the development of nanomechanical devices such as switches, resonators, and sensors.