Atomic and electronic structure of monolayer graphene on 6H-SiC(0001)(3 × 3) : a scanning tunneling microscopy study.

Fanny Hiebel , Pierre Mallet (1) , Laurence Magaud (2) , Jean-Yves Veuillen (1)

1 NEEL - QuNES - Nano-Electronique Quantique et Spectroscopie
2 NEEL - Quan2m - Interactions modulables dans des états quantiques 2D

We present an investigation of the atomic and electronic structure of graphene monolayer islands on the 6H-SiC(0001)(3×3) (SiC(3×3)) surface reconstruction using scanning tunneling microscopy (STM) and spectroscopy (STS). The orientation of the graphene lattice changes from one island to the other. In the STM images, this rotational disorder gives rise to various superlattices with periods in the nm range. We show that those superlattices are moir ́e patterns (MPs) and we correlate their apparent height with the stacking at the graphene/SiC(3×3) interface. The contrast of the MP in STM images corresponds to a small topographic modulation (by typically 0.2 ̊A) of the graphene layer. From STS measurements we find that the substrate surface presents a 1.5 eV wide bandgap encompassing the Fermi level. This substrate surface bandgap subsists below the graphene plane. The tunneling spectra are spatially homogeneous on the islands within the substrate surface gap, which shows that the MPs do not impact the low energy electronic structure of graphene. We conclude that the SiC(3 × 3) reconstruction efficiently passivates the substrate surface and that the properties of the graphene layer which grows on top of it should be similar to those of the ideal material.

Mots clés: Graphene on SiC; Scanning Tunneling Microscopy and Spectroscopy; Atomic and Electronic Structure

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Fanny Hiebel, Pierre Mallet, Laurence Magaud, Jean-Yves Veuillen. Atomic and electronic structure of monolayer graphene on 6H-SiC(0001)(3 × 3) : a scanning tunneling microscopy study.. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2009, 80, pp.235429. ⟨10.1103/PhysRevB.80.235429⟩. ⟨hal-00728424⟩