Structural, Optical and Electrical Properties of Cobalt Doped ZnO Quantum Dots

In this study we investigated the optical and electronic properties of cobalt doped Zinc Oxide (ZnO) nanoparticles (quantum dots) fabricated by a precipitation method. We observed significant reduction in ZnO nanoparticle diameter as we increased the percentage of cobalt. UV-VIS absorption measurement show a systematic increase in bandgap from 3.40 eV to 3.69 eV as the cobalt percentage is increased from 0 to 15%. This increase in bandgap is consistent with the confinement effects observed in quantum dots. Photoluminescence studies show a blue shift in near band absorption as the cobalt doping percentage is increased from 0% to 15%. Fluorescence life time measurements of the doped and undoped ZnO samples show a reduction in radiative life time as the cobalt percentage is increased. Electrical properties of doped and undoped samples show that the series resistance in a Cole-Cole plot decreases systematically with higher doping percentage. We will discuss the quantitative changes observed in structural, optical and electrical properties of ZnO quantum dots as the doping percentage is varied from 0 -15%. 1Department of Physics and Engineering Physics, Keplinger Hall, University of Tulsa, OK, 74104 *Corresponding author