Extraordinary epitaxial alignment of graphene islands on Au(111)

TL;DR

This study demonstrates that graphene islands grown on Au(111) align predominantly in a specific orientation, forming a weakly coupled, epitaxial monolayer that retains its electronic properties, highlighting Au(111) as a promising substrate for high-quality graphene growth.

Contribution

It reveals the extraordinary epitaxial alignment of graphene islands on Au(111), showing a preferred orientation despite weak coupling and non-lattice matching, which is unexpected.

Findings

Over 95% of graphene islands are aligned with each other and the substrate.

The dominant orientation aligns graphene [01] with Au [011], not the lattice-matched 30° rotation.

The electronic dispersion of graphene is preserved on Au(111).

Abstract

Pristine, single-crystalline graphene displays a unique collection of remarkable electronic properties that arise from its two-dimensional, honeycomb structure. Using in-situ low-energy electron microscopy, we show that when deposited on the (111) surface of Au carbon forms such a structure. The resulting monolayer, epitaxial film is formed by the coalescence of dendritic graphene islands that nucleate at a high density. Over 95% of these islands can be identically aligned with respect to each other and to the Au substrate. Remarkably, the dominant island orientation is not the better lattice-matched 30^{\circ} rotated orientation but instead one in which the graphene [01] and Au [011] in-plane directions are parallel. The epitaxial graphene film is only weakly coupled to the Au surface, which maintains its reconstruction under the slightly p-type doped graphene. The linear electronic dispersion characteristic of free-standing graphene is retained regardless of orientation. That a weakly interacting, non-lattice matched substrate is able to lock graphene into a particular orientation is surprising. This ability, however, makes Au(111) a promising substrate for the growth of single crystalline graphene films.