Photoluminescence of hydrothermally epitaxied ZnO films

In this study, epitaxial ZnO films were grown hydrothermally on (1 1 1)-oriented single crystal MgAl2O4 substrates at 150 °C from aqueous precursor solutions. It was observed that the film morphology varied with the pH value of the precursor solution, giving pitted films at higher pH and smooth films at lower pH. The photoluminescence spectra of these ZnO films showed a strong near band-edge ultraviolet emission together with deep level emission bands comprised of green and orange-red luminescence. The green band centred around 500 nm was attributed to the presence of Zn vacancies, whereas the orange-red band centred around 650 nm could be related to the presence of oxygen interstitials.