Optical absorption study of 100-MeV chlorine ion-irradiated hydroxyl-free ZnO semiconductor quantum dots

We report here synthesis and optical absorption study of energetic ion-irradiated hydroxyl-free ZnO semiconductor quantum dots. Quantum dot samples were synthesized by a quenching technique and 100-MeV chlorine ion was selected for the irradiation experiment with doses ${\text{1×10}}^{11},$ ${\text{5×10}}^{11},$ ${\text{5×10}}^{12},$ and ${10}^{13}\hspace{0.17em}{\mathrm{ions/cm}}^2.$ With an increase in fluence, the optical absorption spectra of irradiated quantum dots reveal redshift of the energy-gap parameter with respect to unirradiated (virgin) quantum dots. The narrowing of the energy gap of nanoparticles indicate particle growth under ion irradiation which is confirmed from transmission electron microscope images. The possible reason for such variations was encountered using an effective-mass approximation model which fits well for small effective mass and high-dielectric constant ${\mathrm{(\epsilon }}_0\mathrm{).}$