Institute of Applied Physics, Wiedner Hauptstrasse 8-10, Vienna University of Technology, 1040 Vienna, Austria.
Institute of Materials Chemistry, Getreidemarkt 9, Vienna University of Technology, 1060 Vienna, Austria.
Science. 2014 Dec 5;346(6214):1215-8. doi: 10.1126/science.1260556.
Iron oxides play an increasingly prominent role in heterogeneous catalysis, hydrogen production, spintronics, and drug delivery. The surface or material interface can be performance-limiting in these applications, so it is vital to determine accurate atomic-scale structures for iron oxides and understand why they form. Using a combination of quantitative low-energy electron diffraction, scanning tunneling microscopy, and density functional theory calculations, we show that an ordered array of subsurface iron vacancies and interstitials underlies the well-known (√2 × √2)R45° reconstruction of Fe3O4(001). This hitherto unobserved stabilization mechanism occurs because the iron oxides prefer to redistribute cations in the lattice in response to oxidizing or reducing environments. Many other metal oxides also achieve stoichiometry variation in this way, so such surface structures are likely commonplace.
氧化铁在多相催化、制氢、自旋电子学和药物输送等领域发挥着越来越重要的作用。在这些应用中，表面或材料界面可能会限制性能，因此确定氧化铁的准确原子尺度结构并了解其形成原因至关重要。我们使用定量低能电子衍射、扫描隧道显微镜和密度泛函理论计算的组合，表明在众所周知的 Fe3O4(001)的 (√2 × √2)R45°重构之下存在亚表面铁空位和间隙的有序排列。这种迄今为止尚未观察到的稳定化机制的发生是因为铁氧化物倾向于在晶格中重新分布阳离子以响应氧化或还原环境。许多其他金属氧化物也以这种方式实现化学计量变化，因此这种表面结构可能很常见。
