Stabilization of primary mobile radiation defects in MgF₂ crystals

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• 作者：V.M. Lisitsyn^a ; L.A. Lisitsyna^b ; A.I. Popov^c ; ^{popov@ill.fr" class="auth_mail" title="E-mail the corresponding author} ; ^{popov@latnet.lv" class="auth_mail" title="E-mail the corresponding author} ; E.A. Kotomin^c ; ^d ; F.U. Abuova^e ; A. Akilbekov^e ; J. Maier^d
• 关键词：Rutile MgF2 ; Excitons ; Radiation defects ; H and F centers ; First principles calculations
• 刊名：Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
• 出版年：2016
• 出版时间：1 May 2016
• 年：2016
• 卷：374
• 期：Complete
• 页码：24-28
• 全文大小：729 K

文摘

Non-radiative decay of the electronic excitations (excitons) into point defects (F–H pairs of Frenkel defects) is main radiation damage mechanism in many ionic (halide) solids. Typical time scale of the relaxation of the electronic excitation into a primary, short-lived defect pair is about 1–50 ps with the quantum yield up to 0.2–0.8. However, only a small fraction of these primary defects are spatially separated and survive after transformation into stable, long-lived defects. The survival probability (or stable defect accumulation efficiency) can differ by orders of magnitude, dependent on the material type; e.g. ∼10% in alkali halides with f.c.c. or b.c.c. structure, 0.1% in rutile MgF₂ and <0.001% in fluorides MeF₂ (Me: Ca, Sr, Ba). The key factor determining accumulation of stable radiation defects is stabilization of primary defects, first of all, highly mobile hole H centers, through their transformation into more complex immobile defects. In this talk, we present the results of theoretical calculations of the migration energies of the F and H centers in poorely studied MgF₂ crystals with a focus on the H center stabilization in the form of the interstitial F₂ molecules which is supported by presented experimental data.