Abstract
Atomic layer deposition allows the fabrication of BaTiO3 (BTO) ultrathin films with tunable dielectric properties, which is a promising material for electronic and optical technology. Industrial applicability necessitates a better understanding of their atomic structure and corresponding properties. Through the use of element-specific X-ray absorption near edge structure (XANES) analysis, O K-edge of BTO as a function of cation composition and underlying substrate (RuO2 and SiO2) is revealed. By employing density functional theory and multiple scattering simulations, we analyze the distortions in BTO’s bonding environment captured by the XANES spectra. The spectral weight shifts to lower energy with increasing Ti content and provides an atomic scale (microscopic) explanation for the increase in leakage current density. Differences in film morphologies in the first few layers near substrate–film interfaces reveal BTO’s homogeneous growth on RuO2 and its distorted growth on SiO2. This work links structural changes to BTO thin-film properties and provides insight necessary for optimizing future BTO and other ternary metal oxide-based thin-film devices.
Highlights
The perovskite BaTiO3 (BTO) exhibits high dielectric constants,[1,2] ferroelectricity,[3] piezoelectricity,[4] and photorefractive effects,[5] making it a promising material for electronic and optical devices
Together with atomic layer deposition (ALD)’s unique self-limiting surface reactions,[10] researchers foresee its potential in dynamic random-access memory applications,[11,12] in which BTO, conformally coated on high-aspect ratio trenches, may decisively contribute to increasing the memory density necessary for further device miniaturization
As for MgO/ZnO and Al2O3/ZnO ALD,[13,14] metal-oxide (MO) ALD typically renders multicomponent nanolaminate stacks with different materials spatially localized in discrete layers separated by sharp boundaries.[15]
Summary
Ba 4f 14 eV above the Fermi level. substrate, and postprocess annealing. In contrast to the stoichiometric case, the conduction band comprises Ti 4p and high-energy Ba 4f and 5d states hybridized with O 2p .[31] The increase of B (marked by arrow) and a splitting of A derives from Ti−O−Ti asymmetric bond distances in the BTO lattice, leading to a more pronounced electron density depletion on one side of Ti than on the other.[29] This lattice distortion seems larger with more Ba content, which is observable in the pre-edge of Ti L3 spectra (Figure S3a). Author Contributions ⊥J.T., S.A., and A.D. contributed to this work
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