TY - JOUR

T1 - Understanding amorphization mechanisms using ion irradiation in situ a TEM and 3D damage reconstruction

AU - Camara, Osmane

AU - Tunes, Matheus A.

AU - Greaves, Graeme

AU - Mir, Anamul H.

AU - Donnelly, Stephen

AU - Hinks, Jonathan A.

PY - 2019/8/29

Y1 - 2019/8/29

N2 - In this work, ion irradiations in-situ of a transmission electron microscope are performed on single-crystalgermanium specimens with either xenon, krypton, argon, neon or helium. Using analysis of selected area dif-fraction 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 va-cancies) the mechanisms behind amorphization are revealed. An intriguing finding regarding the thresholddisplacements per atom (dpa) required for amorphization results from this study: even though the heavier ionsgenerate more displacements than lighter ions, it is observed that the threshold dpa for amorphization is lowerfor the krypton-irradiated specimens than for the xenon-irradiated ones. The 3D reconstructions of the collisioncascades show that this counter-intuitive observation is the consequence of a heterogeneous amorphizationmechanism. 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, thestochastic nature of the collision cascade ensures complete amorphization via the accumulation of large clustersof defects and even amorphous zones generated by single-helium-ion strikes.

AB - In this work, ion irradiations in-situ of a transmission electron microscope are performed on single-crystalgermanium specimens with either xenon, krypton, argon, neon or helium. Using analysis of selected area dif-fraction 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 va-cancies) the mechanisms behind amorphization are revealed. An intriguing finding regarding the thresholddisplacements per atom (dpa) required for amorphization results from this study: even though the heavier ionsgenerate more displacements than lighter ions, it is observed that the threshold dpa for amorphization is lowerfor the krypton-irradiated specimens than for the xenon-irradiated ones. The 3D reconstructions of the collisioncascades show that this counter-intuitive observation is the consequence of a heterogeneous amorphizationmechanism. 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, thestochastic nature of the collision cascade ensures complete amorphization via the accumulation of large clustersof defects and even amorphous zones generated by single-helium-ion strikes.

KW - Amorphization mechanisms

KW - Displacement per atom

KW - In-situ TEM

KW - Radiation damage

KW - Semiconductors

UR - http://www.scopus.com/inward/record.url?scp=85072723015&partnerID=8YFLogxK

U2 - 10.1016/j.ultramic.2019.112838

DO - 10.1016/j.ultramic.2019.112838

M3 - Article

C2 - 31585253

AN - SCOPUS:85072723015

VL - 207.2019

JO - Ultramicroscopy

JF - Ultramicroscopy

SN - 0304-3991

IS - December

M1 - 112838

ER -