Understanding amorphization mechanisms using ion irradiation in situ a TEM and 3D damage reconstruction

Osmane Camara; Matheus A Tunes; Graeme Greaves; Anamul H Mir; Stephen Donnelly; Jonathan A Hinks

doi:10.1016/j.ultramic.2019.112838

Understanding amorphization mechanisms using ion irradiation in situ a TEM and 3D damage reconstruction

Ultramicroscopy. 2019 Dec:207:112838. doi: 10.1016/j.ultramic.2019.112838. Epub 2019 Aug 29.

Authors

Osmane Camara¹, Matheus A Tunes², Graeme Greaves², Anamul H Mir², Stephen Donnelly², Jonathan A Hinks²

Affiliations

¹ School of Computing and Engineering, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, United Kingdom. Electronic address: osmane.camara@hud.ac.uk.
² School of Computing and Engineering, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, United Kingdom.

PMID: 31585253
DOI: 10.1016/j.ultramic.2019.112838

Abstract

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.

Keywords: Amorphization mechanisms; Displacement per atom; In-situ TEM; Radiation damage; Semiconductors.