Untersuchungen zur elektronischen und atomaren Struktur von SiC-Oberflächen
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Date
2000-02-24
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Universität Dortmund
Abstract
In der vorliegenden Arbeit wird eine Untersuchung zur Struktur Si-terminierter Siliziumkarbid-Oberflächen vorgestellt. Zum Einsatz kamen dabei verschiedene elektronenspektroskopische Methoden, insbesondere die winkelaufgelöste direkte und die inverse Photoemission.
Am Synchrotronstrahlungslabor MAX-Lab in Schweden sind Messungen mit hoher Energie-auflösung an den (2X1)- und c(4X2)-Rekonstruktionen der 3C-SiC(001)-Oberfläche durchgeführt worden. Die Ergebnisse an beiden Oberflächen werden mit theoretischen ab initio Berechnungen der Bandstruktur verglichen und die vorhandenen Modellvorschläge diskutiert. Die gezeigten Untersuchungen an den (Sqrt 3 X Sqrt 3)-R30°- und (3 X 3)-rekonstruierten (0001)-Oberflächen des Polytyps 6H-SiC geben erstmalig Informationen sowohl über die besetzten als auch die unbesetzten Elektronenzustände dieser Oberflächen. Beide Rekonstruktionen sind im Gegensatz zu früheren theoretischen Arbeiten halbleitend. Erst unter Berücksichtigung neuerer Berechnungen, die auf einer Viel-Teilchen-Theorie im Mott-Hubbard-Modell basieren, kann eine gute Übereinstimmung zwischen Experiment und Theorie erzielt werden.
Scope of this thesis is the investigation of the structure of Si-terminated silicon carbide surfaces. Different electron spectroscopic methods are used, especially angle-resolved direct and inverse photoemission. High-resolution photoemission measurements of the (2X1)- and c(4X2)-reconstructions of the 3C-SiC(001)-surface were performed at the MAX-Lab synchrotron radiation facility in Sweden. The results of both surfaces are compared to ab initio calculations of the bandstructure and are discussed in relation to the proposed models. The presented investigations of the (Sqrt 3 X Sqrt 3)-R30°- and (3 X 3)-reconstructions of the 6H-SiC(0001) surface give for the first time simultaneous information about the occupied and also about the unoccupied bandstructure. The surface electronic structure of both reconstructions is semiconducting, contrary to earlier theoretical predictions. However, the semiconducting character and the measured bandgap is in good agreement with recent theoretical results, where many-body electron-electron correlation effects are taken into account, leading to a Mott-Hubbard ground state.
Scope of this thesis is the investigation of the structure of Si-terminated silicon carbide surfaces. Different electron spectroscopic methods are used, especially angle-resolved direct and inverse photoemission. High-resolution photoemission measurements of the (2X1)- and c(4X2)-reconstructions of the 3C-SiC(001)-surface were performed at the MAX-Lab synchrotron radiation facility in Sweden. The results of both surfaces are compared to ab initio calculations of the bandstructure and are discussed in relation to the proposed models. The presented investigations of the (Sqrt 3 X Sqrt 3)-R30°- and (3 X 3)-reconstructions of the 6H-SiC(0001) surface give for the first time simultaneous information about the occupied and also about the unoccupied bandstructure. The surface electronic structure of both reconstructions is semiconducting, contrary to earlier theoretical predictions. However, the semiconducting character and the measured bandgap is in good agreement with recent theoretical results, where many-body electron-electron correlation effects are taken into account, leading to a Mott-Hubbard ground state.
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Siliziumkarbid, SiC, Oberfläche, Rekonstruktion, Geometrische Struktur, Elektronische Bandstruktur, Oberflächenzustand, Winkelaufgelöste Photoemission, Inverse Photoelektronenspektroskopie, Elektronenkorrelation, Mott-Hubbard-Modell, silicon carbide, surface, reconstruction, geometric structure, electronic bandstructure, surface state, angle-resolved photoemission, inverse photoelectron spectroscopy, Electron correlation, Mott-Hubbard-model