A key to the unique combination of electronic and optical properties in halide perovskite materials lies in their rich structural complexity. However, their radiation sensitive nature limits nanoscale structural characterization requiring dose efficient microscopic techniques in order to determine their structures precisely. In this work, we determine the space-group and directly image the Br halide sites of CsPbBr3, a promising material for optoelectronic applications. Based on the symmetry of high-order Laue zone reflections of convergent-beam electron diffraction, we identify the tetragonal (I4/mcm) structural phase of CsPbBr3 at cryogenic temperature. Electron ptychography provides a highly sensitive phase contrast measurement of the halide positions under low electron-dose conditions, enabling imaging of the elongated Br sites originating from the out-of-phase octahedral rotation viewed along the [001] direction of I4/mcm persisting at room temperature. The measurement of these features and compariso...

中文翻译：

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卤化物钙钛矿结构相和八面体旋转角的测定

卤化物钙钛矿材料中电子和光学特性独特组合的关键在于它们丰富的结构复杂性。然而，它们的辐射敏感性限制了纳米级结构表征，需要剂量有效的显微技术才能精确地确定它们的结构。在这项工作中，我们确定了空间群并直接对 CsPbBr3 的溴卤化物位点进行成像，CsPbBr3 是一种有前途的光电应用材料。基于会聚束电子衍射的高阶劳厄区反射的对称性，我们确定了 CsPbBr3 在低温下的四方 (I4/mcm) 结构相。电子 ptychography 提供了在低电子剂量条件下卤化物位置的高灵敏度相衬测量，能够对源自异相八面体旋转的细长 Br 位点进行成像，该旋转沿 I4/mcm 的 [001] 方向观察并在室温下持续存在。这些特征的测量与比较...