High intense violet luminescence in fluorine doped zinc oxide (FZO) thin films deposited by aerosol assisted CVD

Fluorine doped nanocrystalline zinc oxide (F: ZnO-FZO) thin films with varying fluorine dopant level (0-5%) were prepared on corning glass substrates by aerosol assisted chemical vapor deposition. The films exhibited polycrystalline hexagonal wurtzite structure with preferred orientation along c-axis and crystallinity deteriorated with increasing fluorine. As prepared films were found to be stressed in the range from 1.2 to 1.7 GPa and the amount of stress depends strongly on growth conditions. Undoped ZnO films were in a state of less tensile stress, whereas in FZO, the tensile stress increases with the increasing F. Films exhibit hexagonal platelets morphology analyzed using Field emission scanning electron microscope (FESEM). UV-Vis-NIR transmission studies indicated a increase of energy bandgap and increase of optical transmission with the increase in fluorine. Urbach energy (E-U) of films have also been determined. Raman spectroscopy and photoluminescence (PL) analyses identified the origin of stress due to defects introduced by fluorine. A special emphasis was devoted to E-2 high phonon mode analysis of Raman spectra. High intense violet PL has been achieved at room temperature and intensity improved vigorously with the dopant concentration due to a radiative transition of electrons from zinc vacancies level to the conduction band. (C) 2013 Elsevier B.V. All rights reserved.