Evidence of structural strain in epitaxial graphene layers on 6H-SiC(0001)

Abstract

The early stages of epitaxial graphene layer growth on the Si-terminated 6H-SiC(0001) are investigated by Auger electron spectroscopy (AES) and depolarized Raman spectroscopy. The selection of the depolarized component of the scattered light results in a significant increase in the C-C bond signal over the second order SiC Raman signal, which allows to resolve submonolayer growth, including individual, localized C=C dimers in a diamond-like carbon matrix for AES C/Si ratio of $\sim$3, and a strained graphene layer with delocalized electrons and Dirac single-band dispersion for AES C/Si ratio $>$6. The linear strain, measured at room temperature, is found to be compressive, which can be attributed to the large difference between the coefficients of thermal expansion of graphene and SiC. The magnitude of the compressive strain can be varied by adjusting the growth time at fixed annealing temperature.

4 pages, 2 images - final version

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• First-principles calculations of electrical conductivities of edge-modified graphene nanoribbons: strain effect
• Competing scanning tunneling microscope tip-interlayer interactions for twisted multilayer graphene on the a-plane SiC surface
• Raman Spectroscopy of Graphene under Uniaxial Stress: Phonon Softening and Determination of the Crystallographic Orientation
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• Graphene Manipulation on 4H-SiC(0001) Using Scanning Tunneling Microscopy