Modification of electronic surface states by graphene islands on Cu(111)

TL;DR

This study investigates how graphene islands on Cu(111) surfaces modify local electronic states, revealing shifts in work function, surface state dispersion, and reduced coupling to bulk states through STM analysis.

Contribution

It provides detailed atomic-scale insights into how graphene islands alter the electronic surface states of Cu(111), a novel observation in surface science.

Findings

Rydberg-like image potential states shift to lower energy over graphene islands

Resonance linewidths decrease indicating reduced bulk coupling

Dispersion of Cu(111) Shockley surface state is affected by graphene

Abstract

We present a study of graphene/substrate interactions on UHV-grown graphene islands with minimal surface contamination using \emph{in situ} low-temperature scanning tunneling microscopy (STM). We compare the physical and electronic structure of the sample surface with atomic spatial resolution on graphene islands versus regions of bare Cu(111) substrate. We find that the Rydberg-like series of image potential states is shifted toward lower energy over the graphene islands relative to Cu(111), indicating a decrease in the local work function, and the resonances have a much smaller linewidth, indicating reduced coupling to the bulk. In addition, we show the dispersion of the occupied Cu(111) Shockley surface state is influenced by the graphene layer, and both the band edge and effective mass are shifted relative to bare Cu(111).