Graphene/Au(111) interaction studied by scanning tunneling microscopy

TL;DR

This study uses scanning tunneling microscopy to analyze the structure and interaction of graphene islands on Au(111), revealing weak bonding, surface displacement, and the influence of tunneling currents on surface features.

Contribution

It provides detailed STM observations of graphene on Au(111), quantifies the weak interaction energy, and examines how tunneling conditions affect surface reconstructions.

Findings

Graphene islands are dendritic and cover depressed Au regions.

Weak graphene-Au interaction energy is less than 13 meV per C atom.

Tunneling current influences the Au surface reconstruction.

Abstract

We have used scanning tunneling microscopy to study the structure of graphene islands on Au(111) grown by deposition of elemental carbon at 950{\deg}C. Consistent with low-energy electron microscopic observations, we find that the graphene islands have dendritic shapes. The islands tend to cover depressed regions of the Au surface, suggesting that Au is displaced as the graphene grows. If small tunneling currents are used, it is possible to image simultaneously the graphene/Au moir\'e and the Au herringbone reconstruction, which forms underneath the graphene on cooling from the growth temperature. The delicate herringbone structure and its periodicity remain unchanged from the bare Au surface. Using a Frenkel-Kontorova model we deduce that this striking observation is consistent with an attraction between graphene and Au of less than 13 meV per C atom. Raman spectroscopy supports this weak interaction. However, at the tunneling currents necessary for atomic resolution image of graphene, the Au reconstruction is altered, implying influential tip-sample interactions and a mobile Au surface beneath the graphene.