Abstract
Deep UV photoluminescence (PL) spectroscopy was employed to study the optical properties of mesoscopic zinc oxide (ZnO) particles using the third harmonic laser (λ ~ 260 nm) generated from a Ti: sapphire pulse laser for optical excitation. PL spectrum measured at 15 K exhibits excitonic emissions at 3.362 and 3.375 eV due to the donor bound exciton (DoX) and free exciton (FX) transitions, respectively. The dominant emission peak is observed at around 3.308 eV due to the recombination of free electrons from the conduction band to the holes bound to an acceptor state (FA) along with longitudinal optical (LO) phonon replicas. From the power dependent PL measurement, we observed a redshift of FX and DoX emission peaks with increasing excitation laser power, showing a bandgap renormalization effect. Temperature dependent PL measurements were also performed to explore the bandgap renormalization effect. Fitting of our power dependent PL data with Vashishta, and Kalia model shows the clear trend in a good agreement with the model.
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