Unit cell of graphene on Ru(0001): a 25 x 25 supercell with 1250 carbon atoms

TL;DR

This study reveals a complex 25x25 superstructure of graphene on Ru(0001), showing significant substrate corrugation and strong bonding, which impacts graphene's potential as a template for nanocluster arrays.

Contribution

The paper uncovers a unique superstructure of graphene on Ru(0001) with detailed structural insights, highlighting strong substrate corrugation and bonding mechanisms.

Findings

Graphene forms a 25x25 supercell on 23x23 Ru unit cells.

Significant substrate corrugation affects the superstructure.

Strong bonding involves charge transfer, not van der Waals forces.

Abstract

The structure of a single layer of graphene on Ru(0001) has been studied using surface x-ray diffraction. A surprising superstructure has been determined, whereby 25 x 25 graphene unit cells lie on 23 x 23 unit cells of Ru. Each supercell contains 2 x 2 crystallographically inequivalent subcells caused by corrugation. Strong intensity oscillations in the superstructure rods demonstrate that the Ru substrate is also significantly corrugated down to several monolayers, and that the bonding between graphene and Ru is strong and cannot be caused by van der Waals bonds. Charge transfer from the Ru substrate to the graphene expands and weakens the C-C bonds, which helps accommodate the in-plane tensile stress. The elucidation of this superstructure provides important information in the potential application of graphene as a template for nanocluster arrays.