In this work, ion irradiations in-situ of a transmission electron microscope are performed on single-crystal germanium specimens with either xenon, krypton, argon, neon or helium. Using analysis of selected area diffraction patterns and a custom implementation of the Stopping and Range of Ions in Matter (SRIM) within MATLAB (which allows both the 3D reconstruction of the collision cascades and the calculation of the density of vacancies) the mechanisms behind amorphization are revealed. An intriguing finding regarding the threshold displacements per atom (dpa) required for amorphization results from this study: even though the heavier ions generate more displacements than lighter ions, it is observed that the threshold dpa for amorphization is lower for the krypton-irradiated specimens than for the xenon-irradiated ones. The 3D reconstructions of the collision cascades show that this counter-intuitive observation is the consequence of a heterogeneous amorphization mechanism. Furthermore, it is also shown that such a heterogeneous process occurs even for helium ions, which, on average induce only three recoils per ion in the specimen. It is revealed that at relatively high dpa, the stochastic nature of the collision cascade ensures complete amorphization via the accumulation of large clusters of defects and even amorphous zones generated by single-helium-ion strikes.

中文翻译：

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使用离子辐射原位 TEM 和 3D 损伤重建了解非晶化机制

在这项工作中，使用氙气、氪气、氩气、氖气或氦气对单晶锗样品进行透射电子显微镜的原位离子照射。使用对选定区域衍射图案的分析以及在 MATLAB 中自定义实现物质中离子的停止和范围 (SRIM)（允许碰撞级联的 3D 重建和空位密度的计算），非晶化背后的机制是透露。一项关于非晶化所需的每原子阈值位移 (dpa) 的有趣发现来自该研究：尽管较重的离子比轻离子产生更多的位移，但观察到氪辐照样品的非晶化阈值 dpa 低于对于氙气辐照的。碰撞级联的 3D 重建表明，这种违反直觉的观察是异质非晶化机制的结果。此外，还表明即使对于氦离子，这种异质过程也会发生，平均而言，样品中每个离子仅引起三个反冲。结果表明，在相对较高的 dpa 下，碰撞级联的随机性质通过大量缺陷的积累甚至单氦离子撞击产生的非晶区来确保完全非晶化。