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Published April 21, 2018 | Accepted Version
Journal Article Open

Ordered three-fold symmetric graphene oxide/buckled graphene/graphene heterostructures on MgO(111) by carbon molecular beam epitaxy

Abstract

Theory and experiment demonstrate the direct growth of a graphene oxide/buckled graphene/graphene heterostructure on an incommensurate MgO(111) substrate. X-ray photoelectron spectroscopy, electron energy loss, Auger electron spectroscopy, low energy electron diffraction, Raman spectroscopy and first-principles density functional theory (DFT) calculations all demonstrate that carbon molecular beam epitaxy on either a hydroxylated MgO(111) single crystal or a heavily twinned thin film surface at 850 K yields an initial C layer of highly ordered graphene oxide with C_(3v) symmetry. A 5 × 5 unit cell of carbon, with one missing atom, forms on a 4 × 4 unit cell of MgO, with the three C atoms surrounding the C vacancy surface forming covalent C–O bonds to substrate oxide sites. This leads to a bowed graphene-oxide with slightly modified D and G Raman lines and a calculated band gap of 0.36 eV. Continued C growth results in the second layer of graphene that is stacked AB with respect to the first layer and buckled conformably with the first layer while maintaining C_(3v) symmetry, lattice spacing and azimuthal orientation with the first layer. Carbon growth beyond the second layer yields graphene in azimuthal registry with the first two C layers, but with graphene-characteristic lattice spacing and π → π* loss feature. This 3rd layer is also p-type, as indicated by the 5.6 eV energy loss feature. The significant sp^3 character and C_(3v) symmetry of such heterostructures suggest that spin–orbit coupling is enabled, with implications for spintronics and other device applications.

Additional Information

© 2018 The Royal Society of Chemistry. The article was received on 11 Jan 2018, accepted on 14 Mar 2018 and first published on 14 Mar 2018. Work at UNT was supported by was supported by the NSF under grant no. ECCS-1508991, and in part by C-SPIN, a funded center of STARnet, a Semiconductor Research Corporation (SRC) program sponsored by MARCO and DARPA under task IDs 2381.001 and 2381.006. Work at Buffalo was supported by the NSF under the grant No. ECCS-1509221. Work at UNL was supported by the NSF under grant No. ECCS-1508541. Work at Caltech was supported as part of the Computational Materials Sciences Program funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award Number DE-SC00014607. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1548562. There are no conflicts to declare.

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Created:
August 19, 2023
Modified:
October 18, 2023