The Tip-Induced Twisted Bilayer Graphene Superlattice on HOPG: Capillary Attraction Effect

TL;DR

This paper demonstrates how an STM tip in humid conditions can manipulate graphite sheets to create graphene superlattices, highlighting the role of capillary forces in the process.

Contribution

It introduces a novel method using STM tip-induced capillary attraction to generate graphene superlattices on HOPG surfaces.

Findings

Capillary force is crucial in manipulating graphite sheets.

STM tip can tear and fold graphite to form superlattices.

Method offers a controllable way to produce graphene nanostructures.

Abstract

We use the tip of the scanning tunneling microscope (STM) to manipulate single weakly bound nanometer-sized sheets on the the highly oriented pyrolytic graphite (HOPG) surface through artifically increasing the tip and sample interaction in humid environment. By this means it is possible to tear apart a graphite sheet againt a step and fold this part onto the HOPG surface and thus generate the gaphene superlattices with hexagonal symmetry. The tip and sample surface interactions, including the van der Waals force, eletrostatic force and capillary attraction force originating from the Laplace pressure due to the formation of a highly curved fluid meniscus connecting the tip and sample, are discussed in details to understand the fromation mechnism of graphen superlattice induced by the STM tip. Especially, the capillary force is the key role in manipulating the graphite surface sheet in the hunmidity condition. Our approach may provides a simple and feasible route to prepare the controllable superlattices and graphene nanoribbons but also replenish and find down the theory of generation of graphene superlattice on HOPG surface by the tip.