Substrate induced nanoscale resistance variation in epitaxial graphene

Anna Sinterhauf,Florian Speck,Philip Willke,Thomas Seyller,Martin Wenderoth,Davood Momeni Pakdehi,Philip Schädlich,Hans Werner Schumacher,Christoph Tegenkamp,Georg A Traeger,Klaus Pierz

doi:10.1038/s41467-019-14192-0

Abstract

Graphene, the first true two-dimensional material, still reveals the most remarkable transport properties among the growing class of two-dimensional materials. Although many studies have investigated fundamental scattering processes, the surprisingly large variation in the experimentally determined resistances is still an open issue. Here, we quantitatively investigate local transport properties of graphene prepared by polymer assisted sublimation growth using scanning tunneling potentiometry. These samples exhibit a spatially homogeneous current density, which allows to analyze variations in the local electrochemical potential with high precision. We utilize this possibility by examining the local sheet resistance finding a significant variation of up to 270% at low temperatures. We identify a correlation of the sheet resistance with the stacking sequence of the 6H silicon carbide substrate and with the distance between the graphene and the substrate. Our results experimentally quantify the impact of the graphene-substrate interaction on the local transport properties of graphene.

Highlights

Graphene, the first true two-dimensional material, still reveals the most remarkable transport properties among the growing class of two-dimensional materials
In a series of experiments—based on scanning tunneling potentiometry (STP)[2] or four-point-probe microscopy3—several groups have focused on local properties like the sheet resistance and the impact of scattering centers like single substrate steps[4,5] or the transition from monolayer to bilayer graphene on transport[6,7]
We show that the high quality of epitaxial monolayer graphene samples grown by polymer assisted sublimation growth (PASG) opens a promising way to quantify delicate local transport properties with high precision

Summary

Introduction

The first true two-dimensional material, still reveals the most remarkable transport properties among the growing class of two-dimensional materials. We quantitatively investigate local transport properties of graphene prepared by polymer assisted sublimation growth using scanning tunneling potentiometry These samples exhibit a spatially homogeneous current density, which allows to analyze variations in the local electrochemical potential with high precision. In a series of experiments—based on scanning tunneling potentiometry (STP)[2] or four-point-probe microscopy3—several groups have focused on local properties like the sheet resistance and the impact of scattering centers like single substrate steps[4,5] or the transition from monolayer to bilayer graphene on transport[6,7] From these results, it is qualitatively well understood that the transport properties of epitaxial graphene are not homogeneous on the nanometer scale. Applying the PASG method, it is possible to grow large-scale monolayer graphene sheets without bilayer formation[9,28] on

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