Periodic ripples on thermally annealed Graphene on Cu (110) - Surface reconstruction or Moire pattern?

TL;DR

This study uses STM to analyze the surface patterns of graphene on Cu(110) after thermal annealing, revealing that observed ripples are due to Moiré interference rather than surface reconstruction, indicating complex interface interactions.

Contribution

It demonstrates that the periodic ripples are caused by Moiré patterns from lattice interference, challenging previous assumptions of surface reconstruction.

Findings

Ripples are due to Moiré interference, not surface reconstruction.

Surface reconstruction along [210] is observed after annealing.

Graphene-Cu interface interactions are more complex than previously thought.

Abstract

We have used Ultrahigh Vacuum (UHV) Scanning tunneling microscopy (STM) to investigate the effect of thermal annealing of graphene grown by chemical vapour deposition (CVD) on a Cu(110) foil. We show that the annealing appears to induce a reconstruction of the Cu surface along the [210] direction, with a period of 1.43 nm. Such reconstructions have been ascribed to the tensile strain induced in the Cu surface by differential thermal expansion of it relative to the graphene overlayer, but we show that it is in fact a Moir\'e pattern due to interference between the graphene and the underlying atomic lattice as evidenced by the appearance of an odd-even transition only observed due to mis-orientation of the top layer of a crystal. This highlights that the analysis of STM measurements of graphene on metal surfaces should take such interference into account and that the graphene-Cu interface is more complex than previously thought.