Ribet Stephanie M, Zeltmann Steven E, Bustillo Karen C, Dhall Rohan, Denes Peter, Minor Andrew M, Dos Reis Roberto, Dravid Vinayak P, Ophus Colin
Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA.
International Institute of Nanotechnology, Northwestern University, Evanston, IL 60208, USA.
Microsc Microanal. 2023 Dec 21;29(6):1950-1960. doi: 10.1093/micmic/ozad111.
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 elements, 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 probes with a high degree of phase diversity, which improve information transfer in ptychographic reconstructions.
在扫描透射电子显微镜（STEM）中，生成高分辨率图像通常需要将电子束聚焦到尽可能小的点。然而，用于聚焦电子束的磁透镜不可避免地存在缺陷，会引入限制分辨率的像差。现代STEM通过使用由许多多极元件组成的硬件像差校正器来克服这一问题，但这些设备复杂、昂贵且难以调节。我们展示了一种可作为像差校正器的静电相位板设计。该校正器由环形段组成，每个环形段都是一个独立的双端器件，可对电子束的一部分施加恒定或渐变的相移。我们展示了使用静电校正器时图像分辨率的提高。工程标准要求在探针形成孔径内的大部分电子束被支撑杆阻挡，这导致校正后的探针出现大的探针尾部，这些尾部对中心瓣之外的样品进行采样。我们还展示了该器件如何用于创建其他STEM束轮廓，如涡旋束和具有高度相位多样性的探针，这可改善叠层成像重建中的信息传递。
