Sputtering from swift-ion trails in LiF: A hybrid PIC/MD simulation

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• 作者：Yaroslav Cherednikov ; Si Neng Sun ; Herbert M. Urbassek
• 关键词：Particle-in-cell ; Molecular dynamics ; Ion tracks ; Sputtering ; Coulomb explosion
• 刊名：Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
• 出版年：15 November, 2013
• 年：2013
• 卷：315
• 期：Complete
• 页码：313-317
• 全文大小：1007 K

文摘

We model the sputtering of a LiF crystal induced by swift-ion impact. The impinging ion creates a trail of doubly ionized F⁺ ions, while simultaneously the corresponding electrons are set free. Ions move according to molecular dynamics, while excited electrons are treated by a particle-in-cell scheme. We treat the recombination time of electrons as a free parameter in our model. We find that the energy distribution of sputtered ions consists of 2 groups: a low-energy group centered at <1 eV, and a high-energy group at 7-8 eV. Fast ions (mainly Li⁺) are emitted early; these charge the surface negatively. Later, larger cluster ions and also neutral LiF molecules are emitted. Emission occurs at low angles to the surface normal. A jet along the normal direction can be observed, which is due to the electric field building up at the track surface. With increasing recombination time, processes are colder; sputtering decreases and the non-thermal jet structure becomes stronger.