ZnO thin films with high conductivity and high transparency were grown on Si (1 0 0) substrates by atomic layer deposition. Thickness dependent (43-225 nm) changes in crystallographic, optical and electrical properties are reported and discussed. Increase in film thickness caused a decrease in the bandgap by relaxation of stress in the plane of the film and led to an improvement in crystallinity and conductivity. The optical studies showed a noticeable change towards the contribution of excitonic and phonon replica to the UV-emission band. (C) 2013 Elsevier B.V. All rights reserved.