Direct Measurement of the Magnitude of van der Waals interaction of Single and Multilayer Graphene

TL;DR

This study directly measures the van der Waals forces in single and multilayer graphene, revealing how substrate interactions influence these forces, which is crucial for engineering 2D material heterostructures.

Contribution

It provides the first reliable quantification of van der Waals forces in graphene layers and demonstrates substrate effects using a Lifshitz theory-based model.

Findings

Van der Waals forces scale with layer number in graphene.

Substrate materials can enhance or reduce graphene's van der Waals interactions.

A Lifshitz theory-based model explains substrate influence on van der Waals forces.

Abstract

Vertical stacking of monolayers via van der Waals assembly is an emerging field that opens promising routes toward engineering physical properties of two-dimensional (2D) materials. Industrial exploitation of these engineering heterostructures as robust functional materials still requires bounding their measured properties so to enhance theoretical tractability and assist in experimental designs. Specifically, the short-range attractive van der Waals forces are responsible for the adhesion of chemically inert components and are recognized to play a dominant role in the functionality of these structures. Here we reliably quantify the the strength of van der Waals forces in terms of an effective Hamaker parameter for CVD-grown graphene and show how it scales by a factor of two or three from single to multiple layers on standard supporting surfaces such as copper or silicon oxide. Furthermore, direct measurements on freestanding graphene provide the means to discern the interplay between the van der Waals potential of graphene and its supporting substrate. Our results demonstrated that the underlying substrates could enhance or reduce the van der Waals force of graphene surfaces, and its consequences are explained in terms of a Lifshitz theory-based analytical model.