Atomic and electronic structure of trilayer graphene/SiC(0001): Evidence of Strong Dependence on Stacking Sequence and charge transfer.

Debora Pierucci,Matteo Calandra,Antoine Barbier,Jean-Christophe Girard,Francesco Mauri,Thomas Brumme,Abdelkarim Ouerghi,Mathieu G Silly,Fausto Sirotti

doi:10.1038/srep33487

Abstract

The transport properties of few-layer graphene are the directly result of a peculiar band structure near the Dirac point. Here, for epitaxial graphene grown on SiC, we determine the effect of charge transfer from the SiC substrate on the local density of states (LDOS) of trilayer graphene using scaning tunneling microscopy/spectroscopy and angle resolved photoemission spectroscopy (ARPES). Different spectra are observed and are attributed to the existence of two stable polytypes of trilayer: Bernal (ABA) and rhomboedreal (ABC) staking. Their electronic properties strongly depend on the charge transfer from the substrate. We show that the LDOS of ABC stacking shows an additional peak located above the Dirac point in comparison with the LDOS of ABA stacking. The observed LDOS features, reflecting the underlying symmetry of the two polytypes, were reproduced by explicit calculations within density functional theory (DFT) including the charge transfer from the substrate. These findings demonstrate the pronounced effect of stacking order and charge transfer on the electronic structure of trilayer or few layer graphene. Our approach represents a significant step toward understand the electronic properties of graphene layer under electrical field.

Highlights

The peculiar band structure features of massive Dirac fermions in multilayer graphene are driving intense activity in fundamental research, as well as for applications in generation optoelectronic devices[1]
Other experimental studies have revealed that as rombohedral stacked multilayer graphene (ABC) trilayer graphene, as identified by a peak asymmetry in micro-Raman spectroscopy, has different electrical properties compared to ABA stacking trilayer graphene[10]
The morphology of the trilayer graphene consisting of large and flat domain was confirmed by LEEM

Summary

Introduction

The peculiar band structure features of massive Dirac fermions in multilayer graphene are driving intense activity in fundamental research, as well as for applications in generation optoelectronic devices[1]. By exploiting STM/STS we examine the electronic structure of ABA and ABC trilayer graphene and compared it to DFT calculations, explicitly taking into account the charge transfer from the substrate and the resulting asymmetric electric field. Note that this level dependence cannot be modeled by a rigid shift of the Fermi energy or the commonly used homogeneous background doping method

Methods

Results

Conclusion