We report first-principles calculations of atomic and electronic structures of epitaxial single-layer graphene on Si-terminated 4H-SiC(0 0 0 1) surface under homogeneous transverse electric fields. We find that atomic positions are insensitive to applied electric fields, but the electronic band structures of the graphene layer are shifted in energy, depending strongly on the applied electric fields, while those of the buffer layer are almost unchanged. This effect finally results in field-induced closing of the energy gap at the Dirac energy point and recovery of the conic feature of the low-energy band structures of free-standing graphene, which are verified and analyzed further with a tight-binding model consisting of the single-layer and the buffer-layer graphene only. The recovery of conical dispersion of the single-layer graphene and ambipolar field-effect behavior, despite the band-gap closure under electric field, makes epitaxial single-layer graphene one of the promising alternatives to current state-of-the-art transistors for radiofrequency applications.
Bibliographical noteFunding Information:
H.L. and H.J.C. were supported by the NRF of Korea (Grant No. 2009-0081204 ). H.L. also acknowledges support from the Seoul Science Scholarship. J.I. acknowledges the support of the Core Competence Enhancement Program (2E21580) of KIST through the Hybrid Computational Science Laboratory. Y.-W.S. was supported by Quantum Metamaterials Research Center No. R11-2008-053-01002-0 and Nano R&D program 2008-03670 through the KOSEF funded by the Korean government (MEST). Computational resources have been provided by KISTI Supercomputing Center (Project No. KSC-2008-S02-0004).
All Science Journal Classification (ASJC) codes
- Materials Science(all)