Nano-granular ZnO layers have been grown using a sol-gel synthesis and spin-coating deposition process. Thin films with thicknesses ranging from 15 to 150 am have been obtained by varying the number of deposition cycles and prepared with different synthesis conditions. Morphologies and optical properties have been carefully investigated by joint spectroscopic ellipsometry and atomic force microscopy. A correlation between the evolution of optical properties and grains morphology has been observed It is shown that both synthesis temperature and concentration similarly allow us to change the correlated growth and properties evolution rate. Thickness variation associated to choice of synthesis parameters could be a useful way to tune morphology and optical properties of the nanostructured ZnO layers. (C) 2015 Elsevier B.V. All rights reserved