Graphene has shown great application potential as the host material for next-generation electronic devices. However, despite its intriguing properties, one of the biggest hurdles for graphene to be useful as an electronic material is the lack of an energy gap in its electronic spectra. This, for example, prevents the use of graphene in making transistors. Although several proposals have been made to open a gap in graphene’s electronic spectra, they all require complex engineering of the graphene layer. Here, we show that when graphene is epitaxially grown on SiC substrate, a gap of ≈0.26 eV is produced. This gap decreases as the sample thickness increases and eventually approaches zero when the number of layers exceeds four. We propose that the origin of this gap is the breaking of sublattice symmetry owing to the graphene–substrate interaction. We believe that our results highlight a promising direction for bandgap engineering of graphene.
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We thank A. Geim and A. H. MacDonald for useful discussions and J. Graf for experimental assistance. This work was supported by the National Science Foundation through Grant No. DMR03-49361, the Director, Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering of the US Department of Energy under Contract No. DEAC03-76SF00098 and by the Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory under the Department of Energy Contract No. DE-AC02-05CH11231. A.H.C.N. was supported through NSF grant DMR-0343790. S.Y.Z. thanks the Advanced Light Source Fellowship for financial support.
The authors declare no competing financial interests.
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Zhou, S., Gweon, G., Fedorov, A. et al. Substrate-induced bandgap opening in epitaxial graphene. Nature Mater 6, 770–775 (2007) doi:10.1038/nmat2003
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