Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 55: Poster Session III - MA 141/144 (Methods: Atomic and Electronic Structure; Particles and Clusters; Heterogeneous Catalysis; Semiconductor Substrates: Epitaxy and Growth+Adsorption+Clean Surfaces+Solid-Liquid Interfaces; Oxides and Insulators: Solid-Liquid Interfaces+Epitaxy and Growth; Phase Transitions; Metal Substrates: Adsorption of Inorganic Molecules+Epitaxy and Growth; Surface Chemical Reactions; Bimetallic Nanosystems: Tuning Physical and Chemical Properties; Oxides and insulators: Adsorption; Organic, polymeric, biomolecular films; etc.)

O 55.38: Poster

Wednesday, February 27, 2008, 18:30–19:30, Poster F

First-Principles Investigation of an Epitaxial Silicon Oxynitride Layer on a 6H-SiC(0001) Surface — •Peter Krüger, Björn Baumeier, and Johannes Pollmann — Institut für Festkörpertheorie, Universität Münster

Recently, Shirasawa et al. [1] have experimentally shown that incorporation of nitrogen at the interface of a silicate adlayer on 6H-SiC(0001) leads to the formation of a well ordered, highly stable epitaxial silicon oxynitride (SiON) layer without dangling bond states. Scanning tunneling spectroscopy data for this system show an amazingly large band gap of about 9 eV.

We have investigated the structural and electronic properties of this novel system by employing density functional theory with self-interaction-corrected pseudopotentials. Our results support the structural model inferred from low-energy electron data [1]. In addition, our calculated filled- and empty-state scanning tunneling microscopy images are in excellent agreement with the experimental data clearly revealing that the O and Si surface states, respectively, of the silicate double-layer on top of the system give rise to the observed images. The calculated surface band structure exhibits a surface band gap of 9 eV whose physical origin is clarifed. Further investigations show that SiON overlayers on 6H-SiC(0001) and 6H-SiC(0001) have qualitatively different electronic structures. While the former is free from gap states, the latter possesses two N-derived states in the fundamental band gap.

[1] Shirasawa et al., Phys. Rev. Lett. 98, 136105 (2007)