“…There have been a number of studies on the defects induced by ion implantation in ZnO using Rutherford backscattering, 12,13 photoluminescence and cathodoluminescence, 14 deep-level transient spectroscopy, 15 secondary-ion-mass spectrometry, 16 and other electrical characterization methods. 17,18 In addition to these methods, positron annihilation spectroscopy has recently emerged as a powerful tool for the study of vacancy-type defects in semiconductors. 19 Due to the Coulomb repulsion from the positive-ion cores, positrons are more likely to be trapped by open volume defects where atoms are missing.…”