| 1. |
- Grueneis, A., et al.
(författare)
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Electron-electron correlation in graphite : A combined angle-resolved photoemission and first-principles study
- 2008
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:3, s. 037601-
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Tidskriftsartikel (refereegranskat)abstract
- The full three-dimensional dispersion of the pi bands, Fermi velocities, and effective masses are measured with angle-resolved photoemission spectroscopy and compared to first-principles calculations. The band structure by density-functional theory underestimates the slope of the bands and the trigonal warping effect. Including electron-electron correlation on the level of the GW approximation, however, yields remarkable improvement in the vicinity of the Fermi level. This demonstrates the breakdown of the independent electron picture in semimetallic graphite and points toward a pronounced role of electron correlation for the interpretation of transport experiments and double-resonant Raman scattering for a wide range of carbon based materials.
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| 2. |
- Usachov, D., et al.
(författare)
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Nitrogen-Doped Graphene: Efficient Growth, Structure, and Electronic Properties
- 2011
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 11:12, s. 5401-5407
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Tidskriftsartikel (refereegranskat)abstract
- A novel strategy for efficient growth of nitrogen-doped graphene (N-graphene) on a large scale from s-triazine molecules is presented. The growth process has been unveiled in situ using time-dependent photoemission. It has been established that a postannealing of N-graphene after gold intercalation causes a conversion of the N environment from pyridinic to graphitic, allowing to obtain more than 8096 of all embedded nitrogen in graphitic form, which is essential for the electron doping in graphene. A band gap, a doping level of 300 meV, and a charge-carrier concentration of similar to 8 x 10(12) electrons per cm 2, induced by 0.4 atom % of graphitic nitrogen, have been detected by angle-resolved photoeinission spectroscopy, which offers great promise for implementation of this system in next generation electronic devices.
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| 3. |
- Haberer, D., et al.
(författare)
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Anisotropic Eliashberg function and electron-phonon coupling in doped graphene
- 2013
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 88:8
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Tidskriftsartikel (refereegranskat)abstract
- We investigate, with high-resolution angle-resolved photoemission spectroscopy, the spectral function of potassium-doped quasi-free-standing graphene on Au. Angle-dependent x-ray photoemission and density functional theory calculations demonstrate that potassium intercalates into the graphene/Au interface, leading to an upshift of the K-derived electronic band above the Fermi level. This empty band is what makes this system perfectly suited to disentangle the contributions to electron-phonon coupling coming from the pi band and K-derived bands. From a self-energy analysis we find an anisotropic electron-phonon coupling strength lambda of 0.1 (0.2) for the K Gamma (K M) high-symmetry directions in momentum space, respectively. Interestingly, the high-energy part of the Eliashberg function which relates to graphene's optical phonons is equal in both directions but only in K M does an additional low-energy part appear.
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| 4. |
- Usachov, D., et al.
(författare)
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Quasifreestanding single-layer hexagonal boron nitride as a substrate for graphene synthesis
- 2010
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 82:7
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that freeing a single-atom thick layer of hexagonal boron nitride (h-BN) from tight chemical bonding to a Ni(111) thin film grown on a W(110) substrate can be achieved by intercalation of Au atoms into the interface. This process has been systematically investigated using angle-resolved photoemission spectroscopy, x-ray photoemission, and absorption techniques. It has been demonstrated that the transition of the h-BN layer from the "rigid" into the "quasifreestanding" state is accompanied by a change in its lattice constant. Using chemical vapor deposition, graphene has been successfully synthesized on the insulating, quasifreestanding h-BN monolayer. We anticipate that the in situ synthesized weakly interacting graphene/h-BN double layered system could be further developed for technological applications and may provide perspectives for further inquiry into the unusual electronic properties of graphene.
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