Self-Assembled Zinc Oxide Quantum Dots Using Spray Pyrolysis Methodology

Self-assembled ZnO quantum dots (QDs) have been obtained on different substrates by using the atmospheric spray pyrolysis methodology under well-defined growth conditions. The evolution of size and density of ZnO QDs as a function of precursor concentration, growth temperature, spraying time and spraying rate has been studied. The analysis of the growth process reveals that a mono layer of isolated ZnO QDs grows over a thin (lesser than 10 nm) continuous wetting layer of ZnO. The QDs were characterized by using scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and X-ray photoelectron spectroscopy. X-ray photoelectron spectra from ZnO QDs showed a shift in the binding energy of about 0.57 eV (toward higher energy) with respect to ZnO thin films, which is because in these QDs stress relaxes elastically.