Department of Physics and Astronomy, London Centre for Nanotechnology, University College London, London, UK.
Nat Commun. 2011;2:212. doi: 10.1038/ncomms1219.
Manganites are technologically important materials, used widely as solid oxide fuel cell cathodes; they have also been shown to exhibit electroresistance. Oxygen bulk diffusion and surface exchange processes are critical for catalytic action, and numerous studies of manganites have linked electroresistance to electrochemical oxygen migration. Direct imaging of individual oxygen defects is needed to underpin understanding of these important processes. Currently, it is not possible to collect the required images in bulk, but scanning tunnelling microscopy (STM) could provide such data for surfaces. Here, we report the first atomic resolution images of oxygen defects at a manganite surface. Our experiments also reveal defect dynamics, including oxygen adatom migration, vacancy-adatom recombination and adatom bistability. Beyond providing an experimental basis for testing models describing the microscopics of oxygen migration at transition-metal oxide interfaces, our work resolves the long-standing puzzle of why STM is more challenging for layered manganites than for cuprates.
钙钛矿锰氧化物是一种在技术上非常重要的材料，被广泛用作固体氧化物燃料电池的阴极；研究表明，它们还具有电阻变化效应。氧的体相扩散和表面交换过程对催化作用至关重要，许多关于钙钛矿锰氧化物的研究将电阻变化效应与电化学氧迁移联系起来。要理解这些重要过程，就需要直接对单个氧空位进行成像。目前，还无法在体相内收集到所需的图像，但扫描隧道显微镜（STM）可以为表面提供此类数据。在此，我们首次报道了钙钛矿锰氧化物表面氧空位的原子分辨率图像。我们的实验还揭示了缺陷动力学，包括氧原子的迁移、空位-原子对的复合以及原子的双稳定性。除了为描述过渡金属氧化物界面氧迁移微观过程的模型提供实验依据外，我们的工作还解决了长期以来的难题，即为什么 STM 对层状钙钛矿锰氧化物比对铜氧化物更具挑战性。
