Routes to rupture and folding of graphene on rough 6H-SiC(0001) and their identification

M Temmen,B Kleine Bussmann,M Reichling,O Ochedowski,T R J Bollmann,M Schleberger

doi:10.3762/bjnano.4.69

M Temmen, B Kleine Bussmann + Show 4 more

Open Access

https://doi.org/10.3762/bjnano.4.69

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Journal: Beilstein Journal of Nanotechnology	Publication Date: Oct 7, 2013
Citations: 7	License type: CC BY 2.0

Abstract

Twisted few layer graphene (FLG) is highly attractive from an application point of view, due to its extraordinary electronic properties. In order to study its properties, we demonstrate and discuss three different routes to in situ create and identify (twisted) FLG. Single layer graphene (SLG) sheets mechanically exfoliated under ambient conditions on 6H-SiC(0001) are modified by (i) swift heavy ion (SHI) irradiation, (ii) by a force microscope tip and (iii) by severe heating. The resulting surface topography and the surface potential are investigated with non-contact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM). SHI irradiation results in rupture of the SLG sheets, thereby creating foldings and bilayer graphene (BLG). Applying the other modification methods creates enlarged (twisted) graphene foldings that show rupture along preferential edges of zigzag and armchair type. Peeling at a folding over an edge different from a low index crystallographic direction can result in twisted BLG, showing a similar height as Bernal (or AA-stacked) BLG in NC-AFM images. The rotational stacking can be identified by a significant contrast in the local contact potential difference (LCPD) measured by KPFM.

Highlights

Since its discovery in 2004 [1], graphene, the 2D crystal with a honeycomb lattice of sp2-bonded carbon atoms, has been shown to have unique properties such as high mechanical strength and elasticity, a very high electrical and thermal conductivity, the impermeability to gases, and many others [2]
Twisted few layer graphene (FLG) exhibits electronic properties ranging from Dirac cones found for single layer graphene (SLG) for rotation angles over 15° where the layers are effectively decoupled, to a Fermi velocity renormalization for smaller rotation angles [8,9,10,11]
To discriminate the different bilayer graphene (BLG) stackings, we investigate the topography by noncontact atomic force microscopy (NC-AFM) combined with measuring the local contact potential differences (LCPD) using Kelvin probe force microscopy (KPFM)

Summary

Introduction

Since its discovery in 2004 [1], graphene, the 2D crystal with a honeycomb lattice of sp2-bonded carbon atoms, has been shown to have unique properties such as high mechanical strength and elasticity, a very high electrical and thermal conductivity, the impermeability to gases, and many others [2]. Single layer graphene (SLG) sheets mechanically exfoliated under ambient conditions on 6H-SiC(0001) are modified by (i) swift heavy ion (SHI) irradiation, (ii) by a force microscope tip and (iii) by severe heating.

Results

Conclusion