Phase contrast in transmission electron microscopy based on thin-film phase plates fabricated from metallic glasses

弱相位物体在聚焦明场透射电子显微镜（TEM）图像中仅产生可忽略的对比度。因此，这是该项目的首要目标，以实现在TEM的金属玻璃制成的薄膜相位板的实施相衬。到目前为止，大多数薄膜相位板由无定形碳组成，无定形碳在电子显微镜下会迅速降解，无法常规应用，尽管弱相位物体的对比度增强令人鼓舞。具有非晶结构的金属玻璃由于其高的导电性和在高能电子辐照下的稳定性而具有替代非晶碳的前景。该项目的任务包括：a）选择具有高玻璃形成倾向和高结晶温度的金属玻璃，B）通过溅射沉积模具制造具有非晶结构和均匀厚度的薄膜，以及c）通过分析TEM表征薄膜的微观结构特性。金属玻璃基Zernike和Hilbert相位板的特性将通过使用测试样品和仅显示弱TEM对比度的样品来研究相移、透射率、截止频率和长期稳定性。通过引入由金属玻璃制成的相位板，我们希望在透射电子显微镜中在延长的应用时间内实现相位对比度，并且伪影可以忽略不计。

Weak-phase objects generate only negligible contrast in in-focus bright-field transmission electron microscopy (TEM) images. It is therefore the overarching goal of this project to achieve phase contrast in TEM by implementation of thin-film phase plates fabricated from metallic glasses. Most thin-film phase plates consist up to now of amorphous carbon which suffer from quick degradation in the electron microscope and cannot be routinely applied, despite encouraging contrast enhancements for weak-phase objects. Metallic glasses with an amorphous structure are promising materials to replace amorphous carbon due to their high electrical conductivity and stability under high-energy electron irradiation. The tasks of the project comprise a) the selection of metallic glasses with a high tendency for glass formation and with high crystallization temperature, b) die fabrication of thin films with amorphous structure and homogeneous thickness by sputter deposition and c) the characterization of the thin-film microstructural properties by analytical TEM. The characteristics of the metallic-glass-based Zernike and Hilbert phase plates will be studied with regard to phase shift, transmission, cut-on frequency and long-term stability by using test samples and samples which show only weak TEM contrast. By introducing phase plates fabricated from metallic glasses we expect to achieve phase contrast with negligible artifacts over extended application times in the transmission electron microscope.