Phase plates (PPs) are beneficial devices to improve the phase contrast of life-science objects in cryo-transmission electron microscopy (TEM). The development of the hole-free (HF) PP, which consists of a thin carbon film, has led to impressive results due to its ease in fabrication, implementation and application. However, the phase shift of the HFPP can be controlled only indirectly. The electrostatic Zach PP uses a strongly localized and adjustable electrostatic potential to generate well-defined and variable phase shifts between scattered and unscattered electrons. However, artifacts in phase-contrast TEM images are induced by the presence of the PP rod in the diffraction plane. We present a detailed analysis and comparison of the contrast-enhancing capabilities of both PP types and their emerging artifacts. For this purpose, cryo-TEM images of a standard T4-bacteriophage test sample were acquired with both PP types. Simulated images reproduce the experimental images well and substantially contribute to the understanding of contrast formation. An electrostatic Zach PP was used in this work to acquire cryo-electron tomograms with enhanced contrast, which are of similar quality as tomograms obtained by HFPP TEM.

中文翻译：

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分析低温透射电子显微镜中的对比：静电 Zach 相位板和无孔相位板的比较

相位板 (PP) 是改善低温透射电子显微镜 (TEM) 中生命科学物体相位对比度的有益设备。由薄碳膜组成的无孔 (HF) PP 的开发由于其易于制造、实施和应用而取得了令人瞩目的成果。然而，HFPP 的相移只能间接控制。静电 Zach PP 使用强局部化和可调节的静电势在散射和非散射电子之间产生明确且可变的相移。然而，相差 TEM 图像中的伪影是由衍射平面中 PP 棒的存在引起的。我们对 PP 类型及其新兴工件的对比度增强功能进行了详细分析和比较。以此目的，使用两种 PP 类型获得标准 T4 噬菌体测试样品的低温 TEM 图像。模拟图像很好地再现了实验图像，并大大有助于理解对比度的形成。在这项工作中使用静电 Zach PP 来获取具有增强对比度的低温电子断层图像，其质量与 HFPP TEM 获得的断层图像质量相似。