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Berlin 2005 – scientific programme

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O: Oberflächenphysik

O 15: Postersitzung (Adsorption an Oberfl
ächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Rastersondentechniken, Zeitaufgelöste Spektroskopie, Methoden)

O 15.47: Poster

Friday, March 4, 2005, 17:00–20:00, Poster TU D

Growth and electronic structure of epitaxial Ba0.7Sr0.3O layers on the Si(001) surface — •Anddreas Gerdes, Jan Zachariae, and Herbert Pfnür — Institut für Festkörperphysik, Universität Hannover, Appelstr. 2, 30167 Hannover

We investigated the growth conditions, crystalline quality and stoichiometry of the medium kr≈30) Ba0.7Sr0.3O films using high resolution LEED, UPS, XPS and EELS. Lattice matched Ba0.7Sr0.3O layers were grown on a intermediate layer on the Si(001) substrate in UHV by evaporation of the metals in an ambient oxygen pressure. The quality of oxide layers depends on two conditions: the kind of the intermediate layer and the accurate oxygen dose, which was determined by mass accumulation on a quartz crystal micro balance. A correct fraction of Ba and Sr in the mixed oxide layers leads to well ordered and lattice matched oxide films from a few monolayers up to 20 nm and more. To obtain monocrystalline Ba0.7Sr0.3O layers, although of different quality, it is necessary to start the growth on one of the three following types of intermediate layers: strontium silicide layers Θ≤ 1 ML grown at T≥ 750 C , strontium metal layers Θ> 1 ML grown at T≤ 650 C and the silicate layers (1 ML of Sr2SiO4). The electronic structure, surface roughness and interface oxidation for the growth on different intermediate layers will be discussed.First results of the growth of Ba0.7Sr0.3O on vicinal Si(001) surfaces to generate a stepped insulator surface and the formation mechanism of surface F-centers will also be presented.

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