Structural change in iron implanted potassium bromide crystals

Abstract

Positron annihilation lifetime spectra and X-ray diffraction have been used to investigate the radiation defects produced by Fe + ion implantation in the ionic crystal KBr at the dose of 5×10 15 ions cm −2. We have found that after implantation both the short and long lifetime components of positron annihilation in KBr crystals increase while the annihilation probability of the second lifetime component decreases from 41.7 to 29.3%. This means a decrease in the number of trapping centers by pick-off annihilation since F-centers that already existed in the sample before implantation have aggregated in the halogen sublattice by electronic processes during ion implantation to become larger centers trapping positrons. The X-ray diffraction spectra show new diffraction peaks with rather strong intensities which can be either due to lattice dilation caused by the F-center aggregation, or by metallic ion precipitates.