Theoretical Study on Epitaxial Graphene Growth by Si Sublimation from SiC(0001) Surface

Kageshima, Hiroyuki; Hibino, Hiroki; Yamaguchi, Hiroshi; Nagase, Masao

doi:10.1143/jjap.50.095601

Cited by 11 publications

(26 citation statements)

References 48 publications

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“…However, generally speaking, Si sublimation cannot be limited to the steps and the C supply is not necessarily abundant. Therefore, next we assume that Si atoms sublimate from a terrace and no excess C atoms are supplied from anywhere else, and compare the two results [25].…”

Section: Epitaxial Graphene Growth On a Flat Surfacementioning

confidence: 99%

The physics of epitaxial graphene on SiC(0001)

Kageshima

Hibino²,

Tanabe³

2012

J. Phys.: Condens. Matter

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Various physical properties of epitaxial graphene grown on SiC(0001) are studied. First, the electronic transport in epitaxial bilayer graphene on SiC(0001) and quasi-free-standing bilayer graphene on SiC(0001) is investigated. The dependences of the resistance and the polarity of the Hall resistance at zero gate voltage on the top-gate voltage show that the carrier types are electron and hole, respectively. The mobility evaluated at various carrier densities indicates that the quasi-free-standing bilayer graphene shows higher mobility than the epitaxial bilayer graphene when they are compared at the same carrier density. The difference in mobility is thought to come from the domain size of the graphene sheet formed. To clarify a guiding principle for controlling graphene quality, the mechanism of epitaxial graphene growth is also studied theoretically. It is found that a new graphene sheet grows from the interface between the old graphene sheets and the SiC substrate. Further studies on the energetics reveal the importance of the role of the step on the SiC surface. A first-principles calculation unequivocally shows that the C prefers to release from the step edge and to aggregate as graphene nuclei along the step edge rather than be left on the terrace. It is also shown that the edges of the existing graphene more preferentially absorb the isolated C atoms. For some annealing conditions, experiments can also provide graphene islands on SiC(0001) surfaces. The atomic structures are studied theoretically together with their growth mechanism. The proposed embedded island structures actually act as a graphene island electronically, and those with zigzag edges have a magnetoelectric effect. Finally, the thermoelectric properties of graphene are theoretically examined. The results indicate that reducing the carrier scattering suppresses the thermoelectric power and enhances the thermoelectric figure of merit. The fine control of the Fermi energy position is thought to be key for the practical use of graphene as a thermoelectric material, which could be achieved with epitaxial graphene. All of these results reveal that epitaxial graphene is physically interesting.

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Section: Epitaxial Graphene Growth On a Flat Surfacementioning

confidence: 99%

The physics of epitaxial graphene on SiC(0001)

Kageshima

Hibino²,

Tanabe³

2012

J. Phys.: Condens. Matter

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“…We work out the associated energy barriers characterizing the possible reaction paths, tracking the processes that lead to the formation of the initial carbon seeds from which graphene can subsequently grow. Former DFT calculations for carbon layers on SiC(0001) − were focused mainly on the structural stability of a selected set of carbon overlayers and, as such, they provide little information about the actual reaction mechanisms. From the experimental observation described above, the essential and basic processes of the graphene growth seem to be summarizable in two stages: (i) Si atoms are desorbed from the nanofacet; that is, the bunched atomic steps, migrate to the terrace sites, and are eventually sublimated.…”

Section: Introductionmentioning

confidence: 99%

Microscopic Mechanisms of Initial Formation Process of Graphene on SiC(0001) Surfaces: Selective Si Desorption from Step Edges

et al. 2017

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We report total-energy calculations based on the density-functional theory that clarify microscopic mechanisms of initial stage of graphene formation on the SiC(0001) surface. We explore favorable reactions for desorption of either Si or C atoms from the stepped surface by determining the desorption and the subsequent migration pathways and calculating the corresponding energy barriers for the first time. We find that the energy barrier for the desorption of an Si atom at the step edge and the subsequent migration toward stable terrace sites are lower than that of a C atom by 0.75 eV, indicative of the selective desorption of Si from the SiC surface. We also find that the subsequent Si desorption is an exothermic reaction. This exothermicity comes from the energy gain due to the bond formation of C atoms being left near the step edges. This is certainly a seed of graphene flakes.

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“…Calculations have shown that Si vacancies or C interstitial in the interface layer below the BG o layer lead to lower total surface energies that can give rise to a number of possible large BG o corrugations. 40 Besides the high Si vacancy concentration, there is a significant change in the carbon-silicon spacing in the top SiC bilayer. The C-Si z-spacing, ∆ Si-C , in the SiC bilayer below BG o is 30% shorter compared to a bulk SiC bilayer and half the distance predicted by ab initio calculations in a bulk terminated surface with a BG ML +ML film.…”

Section: Z-zs1(å) σ(å) θ(Mlg)mentioning

confidence: 99%

Structure and evolution of semiconducting buffer graphene grown on SiC(0001)

et al. 2017

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Using highly controlled coverages of graphene on SiC(0001), we have studied the structure of the first graphene layer that grows on the SiC interface. This layer, known as the buffer layer, is semiconducting. Using x-ray reflectivity and x-ray standing waves analysis we have performed a comparative study of the buffer layer structure with and without an additional monolayer graphene layer above it. We show that no more than 26% of the buffer carbon is covalently bonded to Si in the SiC interface. We also show that the top SiC bilayer is Si depleted and is the likely the cause of the incommensuration previously observed in this system. When a monolayer graphene layer forms above the buffer, the buffer layer becomes less corrugated with signs of a change in the bonding geometry with the SiC interface. At the same time, the entire SiC interface becomes more disordered, presumably due to entropy associated with the higher growth temperature.

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Theoretical Study on Epitaxial Graphene Growth by Si Sublimation from SiC(0001) Surface

Cited by 11 publications

References 48 publications

The physics of epitaxial graphene on SiC(0001)

The physics of epitaxial graphene on SiC(0001)

Microscopic Mechanisms of Initial Formation Process of Graphene on SiC(0001) Surfaces: Selective Si Desorption from Step Edges

Structure and evolution of semiconducting buffer graphene grown on SiC(0001)

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