Torgersen Jan, Acharya Shinjita, Dadlani Anup Lal, Petousis Ioannis, Kim Yongmin, Trejo Orlando, Nordlund Dennis, Prinz Fritz B
Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
J Phys Chem Lett. 2016 Apr 21;7(8):1428-33. doi: 10.1021/acs.jpclett.6b00393. Epub 2016 Apr 5.
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.
原子层沉积能够制备出具有可调介电性能的钛酸钡（BTO）超薄膜，这是一种在电子和光学技术领域颇具前景的材料。工业适用性要求我们更好地了解其原子结构和相应性能。通过使用元素特异性X射线吸收近边结构（XANES）分析，揭示了BTO的O K边随阳离子组成和底层衬底（RuO2和SiO2）的变化情况。通过运用密度泛函理论和多重散射模拟，我们分析了XANES光谱所捕捉到的BTO键合环境中的畸变。随着Ti含量的增加，光谱权重向较低能量移动，并为漏电流密度的增加提供了原子尺度（微观）的解释。衬底-薄膜界面附近前几层薄膜形态的差异揭示了BTO在RuO2上的均匀生长及其在SiO2上的畸变生长。这项工作将结构变化与BTO薄膜性能联系起来，并为优化未来的BTO及其他基于三元金属氧化物的薄膜器件提供了必要的见解。
