Precision controlled atomic resolution scanning transmission electron microscopy using spiral scan pathways.
Precision controlled atomic resolution scanning transmission electron microscopy using spiral scan pathways.
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DOI：
10.1038/srep43585
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发表时间：
2017-03-08
影响因子：
4.6
通讯作者：
Unocic RR
中科院分区：
文献类型：
--
作者：
Sang X;Lupini AR;Ding J;Kalinin SV;Jesse S;Unocic RR
像差校正扫描透射电子显微镜（STEM）中的原子分辨率成像可以实现原子结构和材料功能之间的直接关联。然而，STEM探头的快速和精确控制是具有挑战性的，因为根据偏转器的特性，真实的光束位置偏离指定的位置。为了减少这些偏差，即图像失真，我们使用螺旋扫描路径，允许在像差校正STEM内精确控制亚微米尺寸的电子探针。虽然螺旋扫描避免了传统光栅扫描中光束位置的突然变化（回扫失真），但它并非无失真。“阿基米德”螺线，在每次扫描中具有恒定的角频率，用于确定不同频率下的特征响应。然后，我们表明，这样的特征函数可以用来纠正图像失真存在于更复杂的恒定线速度螺旋，其中频率在每次扫描内变化。通过恒定线速度扫描和光束路径校正的组合应用，螺旋扫描图像显示出比传统光栅扫描图像更少的扫描失真。这里提出的方法将是有用的原位STEM成像在更高的时间分辨率和成像束敏感材料。
Atomic-resolution imaging in an aberration-corrected scanning transmission electron microscope (STEM) can enable direct correlation between atomic structure and materials functionality. The fast and precise control of the STEM probe is, however, challenging because the true beam location deviates from the assigned location depending on the properties of the deflectors. To reduce these deviations, i.e. image distortions, we use spiral scanning paths, allowing precise control of a sub-Å sized electron probe within an aberration-corrected STEM. Although spiral scanning avoids the sudden changes in the beam location (fly-back distortion) present in conventional raster scans, it is not distortion-free. “Archimedean” spirals, with a constant angular frequency within each scan, are used to determine the characteristic response at different frequencies. We then show that such characteristic functions can be used to correct image distortions present in more complicated constant linear velocity spirals, where the frequency varies within each scan. Through the combined application of constant linear velocity scanning and beam path corrections, spiral scan images are shown to exhibit less scan distortion than conventional raster scan images. The methodology presented here will be useful for in situ STEM imaging at higher temporal resolution and for imaging beam sensitive materials.