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Effect of ion velocity on creation of point defects halos of latent tracks in LiF

Volkov, A. E. and Schwartz, K. and Medvedev, N. A. and Trautmann, C. (2017):
Effect of ion velocity on creation of point defects halos of latent tracks in LiF.
In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier Science Publishing, pp. 80-85, 407, ISSN 0168583X,
DOI: 10.1016/j.nimb.2017.05.065,
[Online-Edition: https://doi.org/10.1016/j.nimb.2017.05.065],
[Article]

Abstract

Parameters of point defects halos (F-color centers) created due to decays of self-trapped valence holes generated in nanometric vicinities of trajectories of gold ions of 275 MeV and 2187 MeV in LiF are estimated in absorption spectroscopy experiments. Such ions have approximately the same electronic stopping: 24.6 keV/nm and 22.9 keV/nm, respectively. In contrast to the usual concept of the velocity effect that a slower ion produces larger structure changes due to a higher density of the deposited energy, the opposite effect occurs for the defect halo revealing a larger radius and a larger defect concentration for an ion of the higher velocity realizing the same energy loss.

Spatial spreading of generated valence holes before their self-trapping (500 fs) forms the size of the defect halos around the trajectories of the applied ions. Simulations with Monte-Carlo code TREKIS show no significant difference in the initial spatial distributions of these valence holes by the times of finishing of ionization cascades (∼10 fs after the projectile passage) within the radii of the defect halos deduced from the experiments. Using these distributions as initial conditions for spatial spreading of generated valence holes and taking into account the difference between the defect halo radii, the diffusion coefficients of these holes near the trajectories of 275 and 2187 MeV Au ions in LiF are estimated showing about six times larger value in tracks of the faster ion for irradiations at room temperatures.

Presence of H-color centers changes considerably the kinetics of the created defect ensemble in the defect halo resulting in differences between the defect halo parameters in LiF crystals irradiated at 8 K vs. 300 K.

Item Type: Article
Erschienen: 2017
Creators: Volkov, A. E. and Schwartz, K. and Medvedev, N. A. and Trautmann, C.
Title: Effect of ion velocity on creation of point defects halos of latent tracks in LiF
Language: English
Abstract:

Parameters of point defects halos (F-color centers) created due to decays of self-trapped valence holes generated in nanometric vicinities of trajectories of gold ions of 275 MeV and 2187 MeV in LiF are estimated in absorption spectroscopy experiments. Such ions have approximately the same electronic stopping: 24.6 keV/nm and 22.9 keV/nm, respectively. In contrast to the usual concept of the velocity effect that a slower ion produces larger structure changes due to a higher density of the deposited energy, the opposite effect occurs for the defect halo revealing a larger radius and a larger defect concentration for an ion of the higher velocity realizing the same energy loss.

Spatial spreading of generated valence holes before their self-trapping (500 fs) forms the size of the defect halos around the trajectories of the applied ions. Simulations with Monte-Carlo code TREKIS show no significant difference in the initial spatial distributions of these valence holes by the times of finishing of ionization cascades (∼10 fs after the projectile passage) within the radii of the defect halos deduced from the experiments. Using these distributions as initial conditions for spatial spreading of generated valence holes and taking into account the difference between the defect halo radii, the diffusion coefficients of these holes near the trajectories of 275 and 2187 MeV Au ions in LiF are estimated showing about six times larger value in tracks of the faster ion for irradiations at room temperatures.

Presence of H-color centers changes considerably the kinetics of the created defect ensemble in the defect halo resulting in differences between the defect halo parameters in LiF crystals irradiated at 8 K vs. 300 K.

Journal or Publication Title: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Volume: 407
Publisher: Elsevier Science Publishing
Uncontrolled Keywords: Swift heavy ion, Electronic stopping, Track, LiF, Color Centers, Defect halo
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Ion-Beam-Modified Materials
Date Deposited: 29 Dec 2017 12:08
DOI: 10.1016/j.nimb.2017.05.065
Official URL: https://doi.org/10.1016/j.nimb.2017.05.065
Funders: A.E. Volkov acknowledges financial support from grants 15-58-15002 and 15-02-02875 of Russian Foundation for Basic Research; from the Ministry of Education and Science of the Russian Federation in the framework of (a) Project No.16 APPA (GSI),, A.E. Volkov acknowledges financial support from grants (b) Increase Competitiveness Program of NUST «MISiS» (No. K3-2016-035) as well as (c) Competitiveness Program of NRNU MEPhI., Partial financial support from the Czech Ministry of Education (Grants LG15013 and LM2015083) is acknowledged by N.A. Medvedev.
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