Periodically modulated geometric and electronic structure of graphene on Ru(0001)

TL;DR

This paper presents a method to fabricate and analyze highly perfect, periodically rippled graphene monolayers on Ru(0001), revealing inhomogeneous charge distribution and metallic behavior across ripples, with potential applications in quantum dot arrays.

Contribution

It introduces a controlled fabrication technique for periodically rippled graphene on Ru(0001) and characterizes its atomic-scale structure and electronic properties.

Findings

Periodic geometric ripples observed in graphene on Ru(0001).

Charge distribution varies with ripple height, showing inhomogeneity.

Both high and low ripple parts exhibit metallic behavior.

Abstract

We report here on a method to fabricate and characterize highly perfect, periodically rippled graphene monolayers and islands, epitaxially grown on single crystal metallic substrates under controlled UHV conditions. The periodicity of the ripples is dictated by the difference in lattice parameters of graphene and substrate, and, thus, it is adjustable. We characterize its perfection at the atomic scale by means of STM and determine its electronic structure in the real space by local tunnelling spectroscopy. There are periodic variations in the geometric and electronic structure of the graphene monolayer. We observe inhomogeneities in the charge distribution, i.e a larger occupied Density Of States at the higher parts of the ripples. Periodically rippled graphene might represent the physical realization of an ordered array of coupled graphene quantum dots. The data show, however, that for rippled graphene on Ru(0001) both the low and the high parts of the ripples are metallic. The fabrication of periodically rippled graphene layers with controllable characteristic length and different bonding interactions with the substrate will allow a systematic experimental test of this fundamental problem.