In this paper, we reported a Raman scattering study of epitaxial graphene on different doped 6H-SiC ͑0001͒ substrates and investigated the substrate induced charge-transfer doping to the epitaxial graphene. We found that the charge carrier type and concentration of epitaxial graphene can be altered by SiC substrates with different doping level and doping type. This effect is comparable to that obtained by electrochemical doping. As Raman scattering is very sensitive to the doping level, the charge carrier concentration of epitaxial graphene can be estimated by the Raman G-peak shift. Our results are fundamental and may have implications for future epitaxial-graphene-based micro/ nanoelectronic devices.
The electronic properties of epitaxial graphene (EG) on SiC (0001) depend sensitively on the surface morphology of SiC substrate. Here, 2–3 layers of graphene were grown on on-axis 6H-SiC with different step densities realized through controlling growth temperature and ambient pressure. We show that epitaxial graphene on SiC (0001) with low step density and straight step edge possesses fewer point defects laying mostly on step edges and higher carrier mobility. A relationship between step density and EG mobility is established. The linear scan of Raman spectra combined with the atomic force microscopy morphology images revealed that the Raman fingerprint peaks are nearly the same on terraces, but shift significantly while cross step edges, suggesting the graphene is not homogeneous in strain and carrier concentration over terraces and step edges of substrates. Thus, control morphology of epitaxial graphene on SiC (0001) is a simple and effective method to pursue optimal route for high quality graphene and will be helpful to prepare wafer sized graphene for device applications.
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