扫描透射电镜静电像差校正器的设计
Design of Electrostatic Aberration Correctors for Scanning Transmission Electron Microscopy
摘要：
在扫描透射电子显微镜（STEM）中，产生高分辨率图像通常需要电子束聚焦到可能的最小点。然而，用于聚焦光束的磁透镜是不完美的，引入了限制分辨率的像差。现代STEM通过使用由许多多极透镜组成的硬件像差校正器来克服这一点，但是这些设备复杂、昂贵并且可能难以调谐。我们演示了一种静电相位板的设计，可以作为像差校正器。校正器由环形段组成，每个环形段是独立的两端器件，可以向电子束的一部分施加恒定或斜坡相移。我们使用静电校正器的图像分辨率的改善。工程标准强加的探针形成孔径内的大部分光束被支撑杆阻挡，导致校正探针的大探针尾部，其对超出中央瓣的样品进行采样。我们还展示了如何使用该设备来创建其他STEM光束轮廓，如涡旋光束和具有高度相位多样性的光束，这提高了重叠关联重建中的信息传输。
英文摘要：
In a scanning transmission electron microscope (STEM), producing a high-resolution image generally requires an electron beam focused to the smallest point possible. However, the magnetic lenses used to focus the beam are unavoidably imperfect, introducing aberrations that limit resolution. Modern STEMs overcome this by using hardware aberration correctors comprised of many multipole lenses, but these devices are complex, expensive, and can be difficult to tune. We demonstrate a design for an electrostatic phase plate that can act as an aberration corrector. The corrector is comprised of annular segments, each of which is an independent two-terminal device that can apply a constant or ramped phase shift to a portion of the electron beam. We show the improvement in image resolution using an electrostatic corrector. Engineering criteria impose that much of the beam within the probe-forming aperture be blocked by support bars, leading to large probe tails for the corrected probe that sample the specimen beyond the central lobe. We also show how this device can be used to create other STEM beam profiles such as vortex beams and beams with a high degree of phase diversity, which improve information transfer in ptychographic reconstructions.
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