Effect of 100 MeV Nickel Ions on Silica Coated ZnS Quantum Dots

We report synthesis, optical absorption and luminescence spectroscopy of Ni+7 ion irradiated ZnS semiconductor quantum dots over coated with Silica (SiO2) embedded in PVA matrix. Quantum dot samples are prepared via Chemical route. 100 MeV Nickel ion is selected for the irradiation experiment with different doses of 1 x 10(11), 3 x 10(11), 3 x 10(12) and 10(13) ions/cm(2). With an increase in doses, the optical absorption edge of irradiated quantum dots reveal negligible shift with respect to that of unirradiated (virgin) quantum dots. This phenomenon clearly indicates no appraisable change in particle size under ion irradiation which is confirmed from high resolution transmission electron microscope images. It has been observed that like virgin samples, irradiated quantum dots produce similar kind of green luminescence but the emission intensity increases significantly after irradiation due to creation of Zn vacancies by ion irradiation.