Hole-free phase plates (HFPPs), also known as Volta phase plates, were already demonstrated to be well suited for in-focus transmission electron microscopy imaging of organic objects. However, the underlying physical processes have not been fully understood yet. To further elucidate the imaging properties of HFPPs, phase shift measurements were carried out under different experimental conditions. Both positive and negative phase shifts occur depending on the diameter of the zero-order electron beam and the HFPP film temperature. The analysis of Thon ring patterns of an amorphous carbon test sample reveals that the phase-shifting patch can be significantly larger than the size of the zero-order beam on the HFPP film. An HFPP was used for in-focus phase contrast imaging of carbon nanotube (CNT) bundles under positive and negative phase-shifting conditions. The comparison of experimental and simulated images of CNT bundles gives detailed information on the phase shift profile, which depends on the spatial frequency in the vicinity of the zero-order beam. The shape of the phase shift profile also explains halo-like image artifacts that surround the imaged objects.

中文翻译：

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通过实验和模拟研究不同操作条件下透射电子显微镜中无孔相板性能

无孔相位板（HFPP），也称为Volta相板，已被证明非常适合有机物体的聚焦透射电子显微镜成像。但是，尚未完全理解基本的物理过程。为了进一步阐明HFPP的成像特性，在不同的实验条件下进行了相移测量。正相移和负相移都取决于零级电子束的直径和HFPP膜的温度。对无定形碳测试样品的Thon环图形的分析表明，相移斑块可能比HFPP膜上的零级光束大得多。HFPP用于正负相移条件下碳纳米管（CNT）束的聚焦相衬成像。CNT束的实验图像和模拟图像的比较给出了有关相移曲线的详细信息，该相移曲线取决于零阶光束附近的空间频率。相移轮廓的形状还解释了围绕成像对象的类似光晕的图像伪像。