Divacancy clustering in neutron-irradiated and annealed n-type germanium

Loading...
Thumbnail Image
Journal Title
Journal ISSN
Volume Title
School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2008
Major/Subject
Mcode
Degree programme
Language
en
Pages
033202/1-4
Series
Physical Review B, Volume 78, Issue 3
Abstract
We have studied the annealing of vacancy defects in neutron-irradiated germanium. After irradiation, the Sb-doped samples [(Sb)=1.5×10 exp 15 cm exp −3] were annealed at 473, 673, and 773 K for 30 min. The positron lifetime was measured as a function of temperature (30–295 K). A lifetime component of 330 ps with no temperature dependence is observed in as-irradiated samples, identified as the positron lifetime in a neutral divacancy and indicating that the divacancy is stable at room temperature (RT). Annealing at 673 K resulted in an increase in the average positron lifetime, and in addition, the annealed samples further showed a larger lifetime component of 430 ps at RT, which is due to larger vacancy clusters. The average positron lifetime in the samples annealed at 473 K has a definite temperature dependence, suggesting that the divacancies become negative as the crystal recovers and the Fermi level moves upwards in the band gap. Annealing at 673 K, reduces the average lifetime and intensity of the defect component τ2 at RT, indicating that the vacancy clusters have started to anneal. Negative divacancies are still present in the samples after this anneal. Annealing at 773 K is enough to remove all observable vacancy defects.
Description
Keywords
positron annihilation, germanium, divacancy, clusters
Other note
Citation
Kuitunen, K. & Tuomisto, Filip & Slotte, J. & Capan, I. 2008. Divacancy clustering in neutron-irradiated and annealed n-type germanium. Physical Review B. Volume 78, Issue 3. 033202/1-4. ISSN 1098-0121 (printed). DOI: 10.1103/physrevb.78.033202