Scanning nanobeam electron diffraction (NBED) with fast pixelated detectors is a valuable technique for rapid, spatially resolved mapping of lattice structure over a wide range of length scales. However, intensity variations caused by dynamical diffraction and sample mistilts can hinder the measurement of diffracted disk centers as necessary for quantification. Robust data processing techniques are needed to provide accurate and precise measurements for complex samples and non-ideal conditions. Here we present an approach to address these challenges using a transform, called the exit wave power cepstrum (EWPC), inspired by cepstral analysis in audio signal processing. The EWPC transforms NBED patterns into real-space patterns with sharp peaks corresponding to inter-atomic spacings. We describe a simple analytical model for interpretation of these patterns that cleanly decouples lattice information from the intensity variations in NBED patterns caused by tilt and thickness. By tracking the inter-atomic spacing peaks in EWPC patterns, strain mapping is demonstrated for two practical applications: mapping of ferroelectric domains in epitaxially strained PbTiO3 films and mapping of strain profiles in arbitrarily oriented core-shell Pt-Co nanoparticle fuel-cell catalysts. The EWPC transform enables lattice structure measurement at sub-pm precision and sub-nm resolution that is robust to small sample mistilts and random orientations.

中文翻译：

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用于扫描纳米束电子衍射的出波功率倒谱变换：亚纳米分辨率和亚皮米精度下的稳健应变映射

使用快速像素化探测器扫描纳米束电子衍射 (NBED) 是一种有价值的技术，可以在很宽的长度范围内快速、空间分辨地绘制晶格结构。然而，由动态衍射和样品雾化引起的强度变化会阻碍衍射盘中心的测量，这是量化所必需的。需要强大的数据处理技术来为复杂样品和非理想条件提供准确和精确的测量。在这里，我们提出了一种使用变换来解决这些挑战的方法，称为出射波功率倒谱 (EWPC)，其灵感来自音频信号处理中的倒谱分析。EWPC 将 NBED 模式转换为具有对应于原子间距的尖峰的真实空间模式。我们描述了一个简单的分析模型来解释这些图案，该模型将晶格信息与由倾斜和厚度引起的 NBED 图案的强度变化完全分离。通过跟踪 EWPC 图案中的原子间间距峰，应变映射可用于两种实际应用：外延应变 PbTiO3 薄膜中铁电畴的映射和任意取向的核-壳 Pt-Co 纳米颗粒燃料电池催化剂中的应变分布映射。EWPC 变换能够以亚微米精度和亚纳米分辨率进行晶格结构测量，这对小样本雾化和随机取向具有鲁棒性。应变映射被证明用于两个实际应用：外延应变 PbTiO3 薄膜中的铁电畴映射和任意取向的核-壳 Pt-Co 纳米颗粒燃料电池催化剂中的应变分布映射。EWPC 变换能够以亚微米精度和亚纳米分辨率进行晶格结构测量，这对小样本雾化和随机取向具有鲁棒性。应变映射被证明用于两个实际应用：外延应变 PbTiO3 薄膜中的铁电畴映射和任意取向的核-壳 Pt-Co 纳米颗粒燃料电池催化剂中的应变分布映射。EWPC 变换能够以亚微米精度和亚纳米分辨率进行晶格结构测量，这对小样本雾化和随机取向具有鲁棒性。