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O: Oberflächenphysik

O 14: Poster session I (Adsorption, Epitaxy and growth, Phase transitions, Surface reactions, Organic films, Electronic structure, Methods) (sponsored by Omicron Nanotechnology GmbH)

O 14.19: Poster

Montag, 27. März 2006, 18:00–21:00, P2

Theory of hydrogen-induced surface metallization of 3C-SiC(001)-(3x2) — •X. Peng, P. Krüger, and J. Pollmann — Institut für Festkörpertheorie, Wilhelm-Klemm-Str. 10, 48149 Münster

Hydrogenation usually passivates semiconductor surfaces. It has never been thought to be a means of making them metallic. Yet, recent experiments have provided clear evidence for the metallization of the SiC(001)-(3×2) surface by hydrogenation [1]. In order to explain this finding it was conjectured [1] that in a first step monohydride units are formed at the top layer Si dimers. Further H adatoms were assumed to break Si dimers in the third layer and to become bonded to one of the two dimer atoms leaving a Si dangling bond at the other.

In order to contribute to a deeper understanding of this surprising metallization we have investigated a rich variety of hydrogen configurations at the SiC(001)-(3×2) surface by calculating their atomic and electronic structure, phonon frequencies and formation energies within density functional theory. Our results show that the dangling bonds in the third layer, supposed to be essential for surface metallization, are highly unstable. Instead, angular Si-H-Si bridge bonds are formed on the third layer with the H atom located at the center above the two Si atoms. The weakly bound Si-H-Si structure gives rise to the surface metallization. Interestingly, our results show that the formation of dihydride instead of monohydride units at the top layer is energetically even more favorable. In addition, we find that H atoms can also form Si-H-Si bridge bonds on the second layer inducing surface metallization, as well.

[1] V. Derycke et al. Nature Mat. Sci. 2, 247 (2003)