论文标题
使用用振幅领板板形成的探针，通过新相位对比茎增强低空间频率成分
Enhancement of low-spatial-frequency components by a new phase-contrast STEM using a probe formed with an amplitude Fresnel zone plate
论文作者
论文摘要
电子显微镜是可视化亚纳米对象形状的强大工具。然而，对比度与密度分布不成比例，因此对标本的定量理解并不是一件直接的，尤其是对于低对比度的受试者，例如生物标本。为了克服这个问题，我们开发了一种新的相位对比度扫描透射电子显微镜（STEM），其中用振幅领板板（FZP）形成了探头束，并检测了由FZP产生的一阶衍射波产生的最终干扰模式。我们在本文中将其命名为FZP-PC-STEM。振幅FZP是通过使用聚焦离子束（FIB）设备制造的，并使用衍射成像技术收集衍射数据。通过比较实验图像和模拟图像，证实了我们提出的光学模型的有效性。通过这种方法对碳纳米管（CNT）束的观测结果表明，与常规的明亮场茎相比，CNT图像中低空间频率成分的对比度得到了增强。原则上，该方法不需要衍射成像方法中使用的后图像处理，并且可以轻松地将其引入传统的茎系统而无需进行重大修改。还证实了长期运行期间强烈电子辐照方法的稳定性和鲁棒性。我们预计FZP-PC-STEM将广泛适用于对辐射敏感的光元素样品的定量观察，并具有简单易用的操作。
Electron microscopy is a powerful tool for visualizing the shapes of sub-nanometer objects. However, contrast is not in proportional to density distribution, and therefore achieving a quantitative understanding of specimens is not straightforward, especially for low-contrast subjects such as biological specimens. To overcome this problem, we have developed a new phase-contrast scanning transmission electron microscope (STEM) in which a probe beam formed with an amplitude Fresnel zone plate (FZP) and the resulting interference patterns produced by the zeroth and first order diffracted waves generated by the FZP are detected. We name it FZP-PC-STEM hereinafter. The amplitude FZP was manufactured by using focused ion beam (FIB) equipment, and the diffraction data were collected by using diffraction imaging technique. The validity of our proposed optical model was confirmed by comparing experimental and simulated images. Observations of carbon nanotube (CNT) bundles by this method showed that the contrast of low-spatial-frequency components in the CNT image was enhanced, unlike the case in conventional bright-field STEM. This method does not, in principle, require the post-image processing used in the diffraction imaging method, and it can be easily introduced into a conventional STEM system without major modifications. The stability and robustness of the method toward intense electron irradiation during long-time operation were also confirmed. We expect that the FZP-PC-STEM will be widely applicable to quantitative observations of radiation-sensitive light-element specimens, with simple and easy operation.
