Regensburg 2019 – scientific programme
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DS: Fachverband Dünne Schichten
DS 25: Thin Film Properties: Structure, Morphology and Composition (XRD, TEM, XPS, SIMS, RBS, AFM, ...) Part II
DS 25.12: Talk
Friday, April 5, 2019, 12:30–12:45, H32
Epitaxial growth of Ba2SiO4 thin films on Si(001) — •Julian Koch and Herbert Pfnür — Leibniz Universität Hannover, Inst. für Festkörperphysik, Appelstr. 2, 30167 Hannover
Ba2SiO4 is a very promising candidate as a high-k dielectric [1]. Previously, Ba2SiO4 films were grown by diffusion of Si from the Si(001) substrate into a deposited BaO layer [1]. These films featured a high interface trap density, which was most likely a result of the diffusion.
This study aims to improve the structural quality of the Ba2SiO4 films by employing a co-deposition growth method, in which Ba and Si are evaporated simultaneously in an oxygen atmosphere. This eliminates the need for the Si diffusion and allows for control of the interface and the exact stoichiometry.
The chemical composition and the crystallinity of the films are investigated using XPS and SPA-LEED, respectively. The chemical shift of the O 1s peak in XPS enables the detection of excess Ba or Si and can thus be used to adjust the Si/Ba deposition ratio. The films are grown at RT to avoid Si diffusion from the substrate. Growth at higher temperatures is also possible, but the Si deposition rate has to be reduced to offset the diffusion. The epitaxial growth succeeded without any surface passivation or interface layer. However, even with correctly adjusted deposition rates, annealing to 680∘C is needed in order to obtain crystalline films. During the annealing process the film is partially evaporated but the relative concentration of Ba to Si remains unchanged.
[1] S. Islam et al. Phys. Rev. Applied 5, 054006 (2016)