Quantum confinement effect in ZnO thin films grown by pulsed laser deposition

High quality crystalline nanostructured ZnO thin films were fabricated by pulsed laser deposition on (0001) sapphire substrates. The films were investigated by x-ray diffraction, scanning electron microscopy, and optical absorption spectroscopy. The exciton peak energy from absorption spectra was used to determine the band gap energy E-g, which was found to increase systematically with the decrease in the mean grain size and ranged from 3.388 to 3.647 eV. This is consistent with the quantum confinement model and, up until now, not observed in a convincing manner in the ZnO thin films. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3010376]