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O: Fachverband Oberflächenphysik

O 95: Thin Oxides and Oxide Layers I (joint session DS/HL/O)

O 95.1: Vortrag

Donnerstag, 19. März 2020, 09:30–09:45, CHE 91

Atomically sharp epitaxial interface between Ba₂SiO₄ and Si(001) — •Julian Koch and Herbert Pfnür — Leibniz Universität Hannover, Institut für Festkörperphysik

Epitaxial growth of Ba₂SiO₄ on Si(001) is a challenge, since neither crystal symmetry nor lattice constants match in a simple manner, but as we show, it has the potential to become the first high quality crystalline high-k gate dielectric. We combined X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and aberration-corrected scanning transmission electron microscopy (STEM) in order to optimize the epitaxial growth by molecular beam epitaxy. The films were grown by a co-deposition method that requires no diffusion of Si from the substrate. While 400 ^∘C turned out to be sufficient to form chemically homogeneous films, crystalline films required an annealing step to 670−690 ^∘C with the break-up of interfacial Si-O bonds as crucial step. STEM confirms that the interface is atomically sharp and that a single layer of the silicate is changed to a (2× 3) structure at the interface from the (2× 1.5) bulk structure. Electrical measurements on MOS-diodes with this material show small hysteresis in CV-curves, low interface trap densities (< 6× 10¹⁰ cm²eV⁻¹) and low leakage currents.