Future trends in aberration-corrected electron microscopy
Future trends in aberration-corrected electron microscopy
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DOI：
10.1098/rsta.2009.0062
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发表时间：
2009-09-28
期刊：
影响因子：
5
通讯作者：
Rose, Harald H.
中科院分区：
文献类型：
--
作者：
Rose, Harald H.
可达到的样本分辨率由仪器分辨率极限 d(i) 和辐射损伤决定。诸如金属之类的固体物体主要是由于入射电子与原子核碰撞而产生的原子位移而损坏的。通过像差校正，仪器分辨率明显提高。为了在低于大约 100 kV 的电压下实现原子分辨率和大量同等分辨率的像点，我们提出了一种消色差电子光学消球差，它没有色差、球差和总离轴慧差。其各向异性分量可以通过由两个电流方向相反的独立绕组组成的双物镜或通过 TEAM 校正器中使用的斜八极杆来消除。我们通过在低于原子位移碰撞阈值的电压下操作像差校正电子显微镜，并将非散射波的相位移动 pi/2 或将散射波的相位移动 -pi/2 来获得最佳成像条件。在这种负对比度模式下，相位对比度和散射对比度相加具有相同的符号。所提出的 SALVE（亚埃低压电子显微镜）项目的目标是实现用于辐射敏感物体可视化的低压像差校正相位透射电子显微镜。该显微镜将采用无彗差物镜、无障碍相位板和补偿球差和色差的新型校正器。
The attainable specimen resolution is determined by the instrumental resolution limit d(i) and by radiation damage. Solid objects such as metals are primarily damaged by atom displacement resulting from knock-on collisions of the incident electrons with the atomic nuclei. The instrumental resolution improves appreciably by means of aberration correction. To achieve atomic resolution at voltages below approximately 100 kV and a large number of equally resolved image points, we propose an achromatic electron optical aplanat, which is free of chromatic aberration, spherical aberration and total off-axial coma. Its anisotropic component is eliminated either by a dual objective lens consisting of two separate windings with opposite directions of their currents or by skew octopoles employed in the TEAM corrector. We obtain optimum imaging conditions by operating the aberration-corrected electron microscope at voltages below the knock-on threshold for atom displacement and by shifting the phase of the non-scattered wave by pi/2 or that of the scattered wave by -pi/2. In this negative contrast mode, the phase contrast and the scattering contrast add up with the same sign. The realization of a low-voltage aberration-corrected phase transmission electron microscope for the visualization of radiation-sensitive objects is the aim of the proposed SALVE (Sub-angstrom Low-Voltage Electron microscope) project. This microscope will employ a coma-free objective lens, an obstruction-free phase plate and a novel corrector compensating for the spherical and chromatic aberrations.