• Greaves, Graeme
• Tunes, Matheus Araujo
• Donnelly, Stephen
• Camara, Osmane
• Mir, Anamul H.
• Hinks, Jonathan A.

Abstract

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

Topics

• density
• impedance spectroscopy
• cluster
• amorphous
• transmission electron microscopy
• defect
• Germanium