Electronic structure, imaging contrast and chemical reactivity of graphene moir\'e on metals

TL;DR

This study combines experimental microscopy and theoretical calculations to analyze the electronic structure, imaging contrast, and chemical reactivity of graphene moiré patterns on metal surfaces, revealing electronic dominance in imaging and site-specific adsorption properties.

Contribution

It provides detailed insights into the electronic and topographic factors influencing imaging contrast and adsorption sites in graphene moiré on Ir(111), using combined microscopy and DFT methods.

Findings

Electronic contribution dominates STM imaging contrast.

Variation in tip-sample interaction influences adsorption sites.

Electronic structure modulates chemical reactivity of graphene moiré.

Abstract

Realization of graphene moir\'e superstructures on the surface of 4d and 5d transition metals offers templates with periodically modulated electron density, which is responsible for a number of fascinating effects, including the formation of quantum dots and the site selective adsorption of organic molecules or metal clusters on graphene. Here, applying the combination of scanning probe microscopy/spectroscopy and the density functional theory calculations, we gain a profound insight into the electronic and topographic contributions to the imaging contrast of the epitaxial graphene/Ir(111) system. We show directly that in STM imaging the electronic contribution is prevailing compared to the topographic one. In the force microscopy and spectroscopy experiments we observe a variation of the interaction strength between the tip and high-symmetry places within the graphene moir\'e supercell, which determine the adsorption cites for molecules or metal clusters on graphene/Ir(111).