Unoccupied Mott-Hubbard state on the(3×3)R30°reconstructed4H−

Abstract

We have investigated the ͑ ͱ 3 ϫ ͱ 3͒R30°reconstructed 4H-SiC͑0001͒ surface using k ជ -resolved inverse photoemission. Undergoing a Mott-Hubbard transition a formerly half-filled surface band splits into a completely occupied and a completely unoccupied band. We observe a sharp peak at an energy of 1.10 eV above the Fermi level. By mapping the dispersion E͑k ជ ͒ of this surface state we show that it remains above the Fermi level throughout the whole surface Brillouin zone, thus confirming the semiconducting character of the surface. As expected for a strongly correlated system the dispersion is flat with a determined bandwidth of W = ͑0.26± 0.10͒ eV. Including recent ARUPS measurements we are able to deduce a Mott-Hubbard parameter of U = ͑2.2± 0.2͒ eV. These results are in accordance with experiments performed on the 6H-SiC͑0001͒ surface, which shows a slightly different electronic structure. We therefore confirm that the Mott-Hubbard splitting for the ͑ ͱ 3 ϫ ͱ 3͒R30°reconstructed surface is independent of the underlying polytype as predicted by theory.

Triangular Spin-Orbit-Coupled Lattice with Strong Coulomb Correlations: Sn Atoms on a SiC(0001) Substrate

“…We add that the only other adatom system known on SiC (0001) is the self-induced formation of a p 3 reconstruction by (low-Z) Si, via mobile substrate atoms [9]. Photoemission data also suggest a Mott-insulating case [16,17], and U values around 1.6-2.1 eV were inferred [18,19]. Role of the SiC substrate: Hopping and screening.-Based on a 20% reduced adatom spacing in SiC(0001) vs Si(111), one would expect both the hopping parameter and bandwidth of the DB to be increased.…”

“…The only other adatom system known on SiC(0001) is the much less controlled auto-formation of a √3-reconstruction by (low-Z) Si via mobile substrate atoms [8]. Photoemission data also suggest a Mott-insulating case [15,16], and U values ranging from 1.6 -2.1 eV have been inferred [17,18].…”

Tuning 3C-SiC(100)/Si(100) Heterostructure Interface Quality

“…Samples with (3 × 2) or c(2 × 2) LEED patterns show a weak shoulder at about −0.8 eV in the UPS spectra, the distinctive feature of a surface state. − Our results are in good agreement with the literature VB measurements, though the energy and angular resolutions in this work do not allow us to better resolve it. On the other hand, thanks to the IPS angular resolution, the CB spectra show a defined structure at about 1.1 eV assigned to C-Si empty states − even in the polycrystalline SiC films . The broad feature at higher energies of the polycrystalline sample (S2_1050_70) becomes sharper and structured as the long-range surface order increases.…”

Large area scanning probe microscope in ultra-high vacuum demonstrated for electrostatic force measurements on high-voltage devices

“…However, a very nice overview on electronic properties of SiC surfaces and interfaces is given by T. Seyller [ 52 ]. The electronic structure of SiC surfaces suffers from a strong electron correlation induced by a Mott–Hubbard metal–insulator transition [ 53 ] due to a half-filled and hence metallic band arising from dangling bonds. More refined studies employed a 2D Hubbard model indicating that the energy levels of the SiC surface consist of a filled band and an empty band, separated by a Hubbard gap of 1.6 eV.…”