Regensburg 2007 – scientific programme

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O: Fachverband Oberflächenphysik

O 33: Oxides and Insulators: Epitaxy and Growth

O 33.1: Talk

Tuesday, March 27, 2007, 15:45–16:00, H41

Ab-initio study of the epitaxial growth of germanium on SrHfO3(001) using strontium as surfactant — •Andrei Reyes Huamantinco and Peter Blöchl — Clausthal University of Technology, Institute for Theoretical Physics, Leibnizstr. 10, D-38678 Clausthal-Zellerfeld, Germany

The channel in a MOSFET must consist of layers with smooth morphology and low defect density. When germanium (high mobility channel) is deposited on SrHfO3 (high-k oxide) it clusters. Nevertheless, we find that depositing a full monolayer of strontium on SrHfO3(001) and using it as template for germanium overgrowth, inhibits clustering. Formation of the first two epitaxial germanium monolayers occurs via consolidation of so-called germanium zig-zag chains which are pieces of the first and second Ge(001) monolayers, and an structural element of the diamond crystal structure. During consolidation of the zig-zag chains, some atoms from the strontium monolayer diffuse to the surface in order to saturate the germanium dangling bonds. After deposition of two germanium monolayers, the resulting configuration consists of strontium half monolayer at the surface, two epitaxial germanium monolayers, the other half monolayer of strontium that remained at the interface, and SrHfO3(001). Further deposition of germanium results in a surfactant-mediated epitaxial layer-by-layer growth because half monolayer of strontium stabilizes the germanium surface and strontium is not incorporated into bulk germanium. The interfacial half monolayer of strontium stabilizes the interface, and provides adequate valence and conduction band offsets for transistor applications.