Mn2+-induced substitutional structural changes in ZnS nanoparticles as observed from positronannihilation studies

Abstract

Zinc sulfide nanoparticles doped with different concentrations of manganese ions(Mn2+) were synthesized at various temperatures to investigate the effects of substitution and theassociated defect evolution. Positron lifetime and Doppler broadening measurements wereused as probes. The initial stage of defect recovery was dominated by the occupation ofZn2+ vacanciesby Mn2+ ions, bringing in characteristic changes in the positron lifetimes, intensities and Dopplerbroadened lineshape parameters. Detailed analyses considering the presence of one and twotypes of defects were carried out to identify the type of defects which trap positrons atthe different dopant concentrations. Electron paramagnetic resonance studiesindicated increased Mn–Mn interaction and the formation of Mn clusters withfurther doping. The results are in striking contrast to those for nanorods, wherevacancy recombination transformed their interior into regions free of defects.