Atomic electric fields revealed by a quantum mechanical approach to electron picodiffraction.
Atomic electric fields revealed by a quantum mechanical approach to electron picodiffraction.
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DOI：
10.1038/ncomms6653
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发表时间：
2014-12-15
影响因子：
16.6
通讯作者：
Rosenauer, Andreas
中科院分区：
文献类型：
--
作者：
Mueller, Knut;Krause, Florian F.;Beche, Armand;Schowalter, Marco;Galioit, Vincent;Loeffler, Stefan;Verbeeck, Johan;Zweck, Josef;Schattschneider, Peter;Rosenauer, Andreas
通过将电子聚焦在直径为50 μ m的探针上，像差校正扫描透射电子显微镜（STEM）目前正在跨越边界，以探测亚原子细节。一个主要的挑战是使用微分相衬（DPC）显微镜测量原子电场，传统上利用场致衍射图案移位的概念。在这里，我们提出了一个简化的量子理论解释DPC。这使我们能够从像素阵列上记录的衍射强度计算转移到STEM探头的动量，而不是传统的分段明场探测器。的有条不紊的发展产生的原子电场，电荷和电子密度进行模拟作为一个理想的模型系统的二元GaN。然后，我们提出了一个详细的实验研究钛酸锶产生原子电场，全面的模拟验证。通过这种解释和升级的仪器，STEM能够量化原子电场和轻原子的高对比度成像。 电子显微镜的进步使更小的特征能够被探测到，原子电场的测量是一个主要的挑战。为了实现这一目标，Müller等人提出了一种简化的理论方法来提高微分相衬显微镜的分辨率。
By focusing electrons on probes with a diameter of 50 pm, aberration-corrected scanning transmission electron microscopy (STEM) is currently crossing the border to probing subatomic details. A major challenge is the measurement of atomic electric fields using differential phase contrast (DPC) microscopy, traditionally exploiting the concept of a field-induced shift of diffraction patterns. Here we present a simplified quantum theoretical interpretation of DPC. This enables us to calculate the momentum transferred to the STEM probe from diffracted intensities recorded on a pixel array instead of conventional segmented bright-field detectors. The methodical development yielding atomic electric field, charge and electron density is performed using simulations for binary GaN as an ideal model system. We then present a detailed experimental study of SrTiO3 yielding atomic electric fields, validated by comprehensive simulations. With this interpretation and upgraded instrumentation, STEM is capable of quantifying atomic electric fields and high-contrast imaging of light atoms. Advances in electron microscopy are enabling ever smaller features to be probed, with the measurement of atomic electric fields standing as a major challenge. Towards that aim, Müller et al. present a simplified theoretical approach for enhancing the resolution in differential phase contrast microscopy.
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