- Conference date: 5−10 Aug 1992
- Location: Jackson Hole, Wyoming (USA)
The positron annihilation Doppler broadening technique has been used to study the effect of annealing of poly‐crystalline tungsten foils irradiated with 110 keV 85Rb+ ions with doses up to 1012, 1014, 1015, and 1016 85Rb+/cm2, and 1017 83Rb+/cm2. The defect depth distribution after irradiation and subsequent annealing for 15 minutes at temperatures from 300 to 1600 K in steps of 100 K has been monitored by measuring the S‐parameter as a function of the positron incident energy. The shape of the S‐curves of the as‐irradiated samples is explained by trapping of positrons in the near surface region (10 nm) containing Rb‐defect clusters and positron trapping in simple defects created at larger depths due to channeling of Rb. Annealing of the ‘‘deep’’ defects in the tail of the distribution is observed as an increase of S at 15 keV in the 400–600 K temperature interval followed by a decrease of S between 1000 and 1300 K. Above these temperatures S rises again. These observations are assigned to trapping of vacancies at the small Rb‐vacancy complexes causing their growth followed by the release of trapped vacancies. When at still higher temperatures the damage in the tail is recovered positrons diffuse back to the near surface region where large Rb‐vacancy clusters or bubbles with correspondingly high S‐parameter value have been formed.
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