Origin of Doping in Quasi-Free-Standing Graphene on Silicon Carbide

Ristein, J.; Mammadov, Samir; Seyller, Thomas

doi:10.1103/physrevlett.108.246104

Cited by 245 publications

(266 citation statements)

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“…17,[30][31][32] This method takes into account particularly the π -π interactions since the corresponding overlaps are the dominant effect in this weakly interacting system. The underlying SiC buffer [33][34][35][36][37] layer was neglected, since the expected energy contribution to the C 60 total energy due to the vdW interaction is at least an order of magnitude lower than the contribution due to the presence of SLG, 18 considering the large separation of SLG and the buffer layer. 38 In the calculations we used more than 20 different adsorption geometries of C 60 /SLG in a 4 × 4 periodicity.…”

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van der Waals interactions mediating the cohesion of fullerenes on graphene

et al. 2012

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Fullerenes on single-layer epitaxial graphene are a model system to study very faint interactions at a molecular level. By a variable temperature scanning tunneling microscope we have been able to study ordered fullerene layers at 40 K, exclusively bound by van der Waals interactions. The experimentally determined adsorption geometry of the molecules is computationally confirmed only if van der Waals interactions are included in the calculation formalism. The relative orientation of fullerenes in their close-packed arrangement is found to be the crucial factor for determining the total energy. Observation of collective movements of fullerene islands points out the weak coupling to the substrate and the important role of the van der Waals cohesion forces within. Mechanical stability, friction, or adhesion are among the physical properties that strongly depend on van der Waals (vdW) interactions. This is also true for the nanoscale. The nucleation and growth of molecular surface structures involve dynamic processes such as diffusion, molecular rotations, or conformational changes, which rely also on vdW intermolecular interactions. 1,2 Moreover, self-assembly and adsorption studies focus on determining the preferred adsorption site and configuration, the adsorbate-adsorbate interaction, and the distance between the adsorbate and substrate (e.g., Ref. 3).There is an increasing interest in the role of vdW interactions of organic molecules on graphite and other surfaces. 4,5 Generally, long-distance forces as vdW are not described by the most widely used functionals of the density-functional theory (DFT). Thus, in many of the works performed until now they are simply not included. However, when planar systems of carbon-based materials are in question, they require a different approach to the interplay between intermolecular (lateral) and adsorbate-substrate (vertical) interactions in determining the properties of ordered molecular structures. To evidence the important role of the vdW interactions in adsorption processes we have chosen a system of a very weakly interacting substrate and adsorbate, single-layer graphene (SLG) 6 and fullerenes (C 60 ). 7 The fact that both materials consist exclusively of carbon atoms arranged in an atomically thin planar mesh without H or any other atoms inside the atomic structure that could lead to long-range H-bond interactions makes this system a good prototype for a demonstration of the effect of these forces at a molecular level.Thus, we consider the C 60 on SLG grown on 6H-SiC(0001) 8-10 as a model system to test the strength of the vdW forces and mutual interactions that occur between neutral inert nanostructures. C 60 adsorbed on surfaces generally tend to form hexagonal close-packed arrangements 11 in order to optimize their lateral interactions. In very recent studies of C 60 molecules deposited on SLG epitaxially grown on metal, 12,13 it has been shown that the interaction between the molecules and the substrate, and consequently the molecular arrangement, is ruled by the m...

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van der Waals interactions mediating the cohesion of fullerenes on graphene

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“…[90] In contrast, QFEG is known to be p-type doped. [46,90] This change has been explained by the presence of the spontaneous polarization of the hexagonal 6H-SiC substrate, which lowers the Fermi energy to a position 0.28 eV to 0.30 eV below the Dirac point for complete hydrogenation. [90,91] 1.…”

Section: Charge Transfer In Tungsten Diselenide Epitaxial Graphene Hementioning

confidence: 99%

“…[46,90] This change has been explained by the presence of the spontaneous polarization of the hexagonal 6H-SiC substrate, which lowers the Fermi energy to a position 0.28 eV to 0.30 eV below the Dirac point for complete hydrogenation. [90,91] 1. An intrinsic interface dipole energy resulting from charge redistribution within the graphene and WSe 2 layers, separately.…”

Section: Charge Transfer In Tungsten Diselenide Epitaxial Graphene Hementioning

confidence: 99%

Section: Charge Transfer In Tungsten Diselenide Epitaxial Graphene Hementioning

confidence: 99%

“…Epitaxial graphene residing on top of the bu er layer reconstruction of graphitized 6H-SiC(0001) is n-type doped [85,87,88] due to the combination of bulk and interface donor states [89,90] and has a Fermi energy 0.45 eV above the Dirac point. [90] In contrast, QFEG is known to be p-type doped. [46,90] This change has been explained by the presence of the spontaneous polarization of the hexagonal 6H-SiC substrate, which lowers the Fermi energy to a position 0.28 eV to 0.30 eV below the Dirac point for complete hydrogenation.…”

Section: Charge Transfer In Tungsten Diselenide Epitaxial Graphene Hementioning

confidence: 99%

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