%0 Journal Article
%A Koch, Julian
%A Müller-Caspary, Knut
%A Pfnür, Herbert
%T Matching different symmetries with an atomically sharp interface: Epitaxial Ba 2 SiO 4 on Si(001)
%J Physical review materials
%V 4
%N 1
%@ 2475-9953
%C College Park, MD
%I APS
%M FZJ-2021-02906
%P 013401
%D 2020
%X In this paper, we present a comprehensive investigation of the epitaxial growth of Ba2SiO4 on Si(001), a system in which neither crystal symmetry nor lattice constants match in a simple manner. In addition, it has the potential to become the first crystalline high-k gate dielectric. We combined x-ray photoelectron spectroscopy, low-energy electron diffraction, and aberration-corrected scanning transmission electron microscopy (STEM) in order to optimize the epitaxial growth by molecular beam epitaxy. Our focus was on the formation of a high quality crystalline interface. The films were grown by a co-deposition method that requires no diffusion of Si from the substrate. An annealing temperature of 400∘C turned out to be sufficient to form chemically homogeneous films. However, crystalline films require an annealing step to 670–690∘C for the formation of the epitaxial interface necessary for breaking Si-O bonds. 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. Based on our experimental results, we propose a geometrical model for the epitaxial interface. The growth of films with an understoichiometric Si flux leads to the formation of a near-surface Ba silicide that does not restrict the epitaxial silicate growth.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000506605500001
%R 10.1103/PhysRevMaterials.4.013401
%U https://juser.fz-juelich.de/record/893894