Berlin 2018 – scientific programme
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DS: Fachverband Dünne Schichten
DS 11: Thin Film Properties: Structure, Morphology and Composition (XRD, TEM, XPS, SIMS, RBS, AFM, ...): Session II
DS 11.4: Talk
Tuesday, March 13, 2018, 10:15–10:30, H 0111
Structural analysis of epitaxial Ba2SiO4 thin films grown on Si(100) — •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. Epitaxial films grown in a previous study [1] have shown a dielectric constant of 22.8±0.2, band offsets to p-Si(100) of over 2 eV, a high temperature stability up to desorption at around 750 ∘C and an acceptable leakage current of 3 mA/cm2 at -1 V. Unfortunately, these films still feature a high density of interface traps. The primary cause of this is most likely the growth mode of the silicate films, which were produced by heating the Si(100) substrate during the growth of a BaO film, so that a diffusion of Si from the substrate to the film occured turning the BaO into Ba2SiO4. This process resulted in an atomically rough interface in a geometric and possibly also in a chemichal sense. Moreover, only the first 5 nm close to the interface turned out to be crystalline.
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. The chemical composition and the crystallinity of the films are investigated using XPS and SPA-LEED, respectively. To further investigate the crystalline growth, crystal orientation and thickness HRTEM is used.