| 中文摘要 |
電子顯微鏡的在二維影像的高解析度已廣泛應用在材料科學和結構生物學領域。斷層掃描也因可非破壞性地顯現內部三維結構，為臨床醫學成像領域帶來革命性的影響。訊號處理廣泛的用於電機資訊工程，將訊號與噪音分離，從而提取真實資訊。在過去的半個世紀裡，晶體結構內部的缺陷由於能顯著改變材料的物理化學性質，吸引了材料科學家的注意。通過組合幾種全新技術：一、掃描透射電子顯微鏡搭配環形暗場偵測器，獲得原子解析度二維投影圖像。二、質心校準法解決投影對應共同轉軸的問題。三、等斜率斷層重組技術減輕資料遺失問題並實現最佳的三維解析度。四、三維傅立葉維納濾波提升三維重組訊噪比。通過這些組合，在三維斷層重組中達到2.4埃的解析度。觀察到在鉑奈米顆粒內晶界處的原子台階與差排錯位。在最近的發展中，更獲得奈米材料中每個原子的三維座標與化學元素，並用來計算材料的應力和磁性。這個強大的技術為結構與功能材料領域的應用提供了一個獨一無二的工具。
Electron microscopy with the high resolution in planar images has found wide application in materials science and structural biology. Tomography has also made a revolutionary impact of non-destructively revealing threedimensional(3D) structures, especially in clinical medical imaging. Digital signal processing is applied to a broad range of electrical engineering to extract the information from noisy signals. Imperfections inside the crystalline structures have caught material scientists’ eyes due to the capability of significantly changing properties of materials. A remarkable advance in the field of electron tomography has been made by combining several novel techniques: scanning transmission electron microscopy with annular dark-field detector to obtain high-resolution two-dimensional projection images, the center of mass alignment method to solve the misalignment problem, the equally sloped tomography method to achieve best spatial resolution by alleviating the missing wedge problem, and the 3D Wiener filtering to enhance the signal-to-noise ratio. With these combinations, a 2.4-angstrom resolution in the 3D reconstruction is demonstrated. Atomic steps and dislocations at the grain boundary inside a 10nm platinum particle are observed. In the most recent developments, three-dimensional coordinates and chemical species of individual atoms are obtained to calculate the strains and magnetic properties of materials. This powerful technique has raised a great potential for applications to structural and functional materials. |
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