Introduction and recovery of point defects in electron-irradiated ZnO

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© 2005 American Physical Society (APS). This is the accepted version of the following article: Tuomisto, Filip & Saarinen, K. & Look, D. C. & Farlow, G. C. 2005. Introduction and recovery of point defects in electron-irradiated ZnO. Physical Review B. Volume 72, Issue 8. 085206/1-11. ISSN 1098-0121 (printed). DOI: 10.1103/physrevb.72.085206, which has been published in final form at http://journals.aps.org/prb/abstract/10.1103/PhysRevB.72.085206.
Journal Title
Journal ISSN
Volume Title
School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2005
Major/Subject
Mcode
Degree programme
Language
en
Pages
085206/1-11
Series
Physical Review B, Volume 72, Issue 8
Abstract
We have used positron annihilation spectroscopy to study the introduction and recovery of point defects in electron-irradiated n-type ZnO. The irradiation (Eel=2MeV, fluence 6×10 exp 17 cm exp −2) was performed at room temperature, and isochronal annealings were performed from 300 to 600 K. In addition, monochromatic illumination of the samples during low-temperature positron measurements was used in identification of the defects. We distinguish two kinds of vacancy defects: the Zn and O vacancies, which are either isolated or belong to defect complexes. In addition, we observe negative-ion-type defects, which are attributed to O interstitials or O antisites. The Zn vacancies and negative ions act as compensating centers and are introduced at a concentration [VZn]≃cion≃2×10 exp 16 cm exp −3. The O vacancies are introduced at a 10-times-larger concentration [VO]≃3×10 exp 17 cm exp −3 and are suggested to be isolated. The O vacancies are observed as neutral at low temperatures, and an ionization energy of 100 meV could be fitted with the help of temperature-dependent Hall data, thus indicating their deep donor character. The irradiation-induced defects fully recover after the annealing at 600 K, in good agreement with electrical measurements. The Zn vacancies recover in two separate stages, indicating that the Zn vacancies are parts of two different defect complexes. The O vacancies anneal simultaneously with the Zn vacancies at the later stage, with an activation energy of EmV,O = 1.8 ± 0.1 eV. The negative ions anneal out between the two annealing stages of the vacancies.
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Keywords
vacancy, ZnO, irradiation, recovery
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Citation
Tuomisto, Filip & Saarinen, K. & Look, D. C. & Farlow, G. C. 2005. Introduction and recovery of point defects in electron-irradiated ZnO. Physical Review B. Volume 72, Issue 8. 085206/1-11. ISSN 1098-0121 (printed). DOI: 10.1103/physrevb.72.085206