HAADF-STEM tomography is a widely used experimental technique for analyzing nanometer-scale structures of a large variety of materials in three dimensions. It is especially useful for studying crystalline nanoparticles, where conventional TEM tomography suffers from diffraction-related artefacts. Unfortunately, the acquisition of a HAADF-STEM tilt series can easily take up one hour or more, depending on the complexity of the experiment. It is therefore challenging to investigate samples that do not withstand long electron beam illumination or to acquire a large number of tilt series during a single TEM experiment. The latter would facilitate obtaining more statistically representative 3D data, and enable performing dynamic in situ 3D characterizations with a finer time resolution. Various HAADF-STEM acquisition strategies have been proposed to accelerate the tomographic acquisition and reduce the required electron dose. These methods include tilting the holder continuously while acquiring a projection "movie" and a hybrid, incremental, methodology which combines the benefits of the conventional and continuous technique. However, until now an experimental evaluation of these techniques has been lacking. In this paper, the different acquisition strategies will be experimentally compared in terms of speed, resolution and electron dose. This evaluation will be performed based on experimental tilt series, acquired for various metallic nanoparticles with different shapes and sizes. We discuss the necessary data processing and provide a general guideline that can be used to determine the most optimal acquisition strategy for specific electron tomography experiments.

中文翻译：

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纳米粒子的快速与传统 HAADF-STEM 断层扫描：优势和挑战

HAADF-STEM 断层扫描是一种广泛使用的实验技术，用于在三个维度上分析多种材料的纳米级结构。它对于研究晶体纳米粒子特别有用，因为传统的 TEM 断层扫描会出现衍射相关的伪影。不幸的是，根据实验的复杂程度，HAADF-STEM 倾斜系列的获取很容易花费一小时或更长时间。因此，研究不能承受长时间电子束照射的样品或在单个 TEM 实验中获得大量倾斜系列是具有挑战性的。后者将有助于获得更具统计代表性的 3D 数据，并能够以更精细的时间分辨率执行动态原位 3D 表征。已经提出了各种 HAADF-STEM 采集策略来加速断层扫描采集并减少所需的电子剂量。这些方法包括在获取投影“电影”的同时连续倾斜支架，以及结合传统和连续技术优点的混合增量方法。然而，到目前为止，还缺乏对这些技术的实验评估。在本文中，不同的采集策略将在速度、分辨率和电子剂量方面进行实验比较。该评估将基于实验倾斜系列进行，获取具有不同形状和尺寸的各种金属纳米粒子。