Hoang Le Phuong, Spasojevic Irena, Lee Tien-Lin, Pesquera David, Rossnagel Kai, Zegenhagen Jörg, Catalan Gustau, Vartanyants Ivan A, Scherz Andreas, Mercurio Giuseppe
European XFEL, 22869, Schenefeld, Germany.
Max Planck Institute for the Structure and Dynamics of Matter, 22761, Hamburg, Germany.
Sci Rep. 2024 Oct 16;14(1):24250. doi: 10.1038/s41598-024-72805-1.
Understanding the mechanisms underlying a stable polarization at the surface of ferroelectric thin films is of particular importance both from a fundamental point of view and to achieve control of the surface polarization itself. In this study, we demonstrate that the X-ray standing wave technique allows the surface polarization profile of a ferroelectric thin film, as opposed to the average film polarity, to be probed directly. The X-ray standing wave technique provides the average Ti and Ba atomic positions, along the out-of-plane direction, near the surface of three differently strained [Formula: see text] thin films. This technique gives direct access to the local ferroelectric polarization at and below the surface. By employing X-ray photoelectron spectroscopy, a detailed overview of the oxygen-containing species adsorbed on the surface is obtained. The different amplitude and orientation of the local ferroelectric polarizations are associated with surface charges attributed to different type, amount and spatial distribution of the oxygen-containing adsorbates.
从基础研究的角度以及实现对表面极化本身的控制来看，了解铁电薄膜表面稳定极化背后的机制都尤为重要。在本研究中，我们证明了X射线驻波技术能够直接探测铁电薄膜的表面极化分布，而非平均薄膜极性。X射线驻波技术提供了三种不同应变的[化学式：见原文]薄膜表面附近沿面外方向的平均Ti和Ba原子位置。该技术能直接获取表面及表面以下的局部铁电极化情况。通过使用X射线光电子能谱，可得到吸附在表面的含氧化合物的详细概况。局部铁电极化的不同幅度和取向与归因于不同类型、数量和空间分布的含氧化合物吸附物的表面电荷相关。
