Electron interference effects and strong localization in Cu doped ZnO thin films

Electron interference effects and transition from weakly localized to a strongly localized transport regime is observed in Cu doped ZnO thin films grown by pulsed laser deposition on c-sapphire substrates. The doping concentration of Cu was varied from 0% to 10%. Up to the doping concentration of ~ 0.5%, the films showed weakly localized behavior where quantum corrections to conductivity due to electron interference was active. At these doping concentrations, a transition from 3D to 2D weak localization was also observed as the measurement temperature was decreased. But at Cu concentrations of 5% and beyond, the films were found to show behavior of strong localization where the transport at low temperature was dominated by hopping mechanism.