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arXiv 1708.05151cond-mat.mtrl-sci
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薄膜位相板的新材料

New materials for thin-film phase-plates

Leonard F. Henrichs

摘要:

以前用于透射电子显微镜(TEM)的Zernike相位板一直由碳制成。对这些相位板的关键约束是它们在使用期间的快速退化。在这里,首次生产和测试了由金属组成的Zernike相位板。对于新的铝相板,没有观察到类似于碳相板的充电。在使用条件下,铝相位板的稳定性非常好。对于这两种材料,当在后焦平面处将薄膜插入光束中时,观察到图像的傅里叶变换中的失真。该失真是负的、空间频率相关的相移,其不等于焦点改变。对测试的相位板,观察到相移和对比度的增加。Janbroers等人发明的一种技术可以生产出不同类型的自持金属薄膜。在室温下生产的所有金属薄膜都具有多晶结构,而碳薄膜则是无定形的。然而,高结晶度是不利的,由于衍射,导致图像失真和相位板中电子散射的增加。使用低温沉积,获得了将非晶结构与金属的有益性质(例如较低的充电和延长的耐久性)相结合的金属膜。透射电镜研究表明,这些低温薄膜作为Zernike相位板材料具有很大的潜力。用原子力显微镜成功地测量了薄膜与基底之间台阶边缘的厚度。为此,这里开发了一种用于制备非常窄的台阶边缘的技术。

英文摘要:

Previous Zernike phase-plates, for transmission-electron-microscopy (TEM) have always been made out of carbon. A critical constraint on those phase-plates is their fast degradation during use. Here, a Zernike phase-plate consisting out of metal is produced and tested for the first time. For the new aluminium phase-plate, no charging like for the carbon phase-plate is observed. Under conditions of use, the stability of the aluminium phase-plate, is excellent. For both materials, a distortion in the image's Fourier-transformation is observed, when inserting the thin-film into the beam at the back-focal-plane. This distortion is a negative, spatial-frequency dependent phase-shift, that is not equal to a focus-change. A phase-shift and an increase of contrast, is observed for the tested phase-plates. Different types of self-sustaining metal-films are produced with a technique, invented by Janbroers et al. All metal-films, produced at room-temperature, exhibit a polycrystalline structure, while carbon-films are amorphous. However, a high crystallinity is unfavored, causing distortions in the image and an increase of electron-scattering in the phase-plate, due to diffraction. Using cryo-deposition, metal-films are obtained that combine an amorphous structure with beneficial properties of metals such as lower charging and prolonged durability. Investigations with TEM, show a great potential of those cryo-films as material for Zernike phase-plates. Thickness-measurements are successfully carried out with atomic-force-mycroscopy at step-edges between the thin-film and its substrate. For this, a technique for the preparation of very narrow step-edges is developed here.

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