Structural and Spectroscopic Characterizations of ZnO Quantum Dots Annealed at Different Temperatures

Here, we report the synthesis and characterizations of sol-gel derived zinc oxide (ZnO) quantum dots (QDs) using zinc acetate dihydrate (Zn(CH3COO)2·2H2O) and lithium hydroxide monohydrate (LiOH·H2O) as raw material. The as-prepared ZnO QDs was annealed at different temperature (400, 700, and 900 °C) and the structural, optical properties were investigated by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), UV-Vis and photoluminescence (PL) spectroscopy. The powder XRD patterns of the obtained samples showed the formation of single-phase wurtzite structure and the morphological changes have been observed with increasing annealing temperature. In the absorption spectra, the optical band gap of nanocrystalline ZnO QDs decreased from 3.18 to 3.11 eV and the particle size increased with increasing temperature. In the PL spectra, a broad green emission peak related to defect levels in the visible range of the spectra have been recorded.