Transmission electron microscope observation of cracks introduced in bulk crystals

材料断裂是材料科学中的重要课题之一。研究材料断裂有两种方法。一种是宏观的，另一种是用计算机进行的原子模拟。然而，在这两个极端之间存在着巨大的差距，正是介观尺度上的信息弥合了这一差距。为了在介观尺度上获得这些信息，透射电子显微镜应该是最合适的技术。然而，要制备包含裂纹尖端的箔试样是极其困难的。本研究的目的是通过透射电子显微镜检查在块状晶体中引入的裂纹，应用聚焦离子束技术从预先选择的区域（如裂纹尖端）制备薄箔样品。这在很大程度上弥补了宏观方法与原子模拟之间的差距。本研究以Si、GaAs、氧化铝和准晶为试样，对裂纹尖端及其附近的缺陷结构进行了全面观察。

Fracture of materials is one of the most important subjects in materials science. There are two approaches to the study of fracture of materials. One is macroscopic one and the other is atomistic simulation using a computer. However, there is a big gap between these extremes and it is information on mesoscopic scale that bridges this gap. In order to get such information on mesoscopic scale transmission electron microscopy should be the most appropriate technique. However, it is extremely difficult to prepare a foil specimen which contain S the very tip of a crack.The purpose of the present study is to examine by transmission electron microscopy those cracks which were introduced in bulk crystals applying a focused ion beam technique to preparation of a thin foil specimen from pre-selected area such as a crack tip. This contributes much to bridge the gap between macroscopic approach and atomistic simulation. In this study, Si, GaAs, alumina and quasicrystals were used as specimens and the defect structures at and near the tips of the cracks were observed comprehensively.