Metal-like conductivity in transparent Al:ZnO films

This letter reports on the metal-like conductivity down to 125K in highly crystalline transparent (⩾85% in the visible region) Al:ZnO films grown on sapphire and glass substrates by pulsed-laser deposition technique. Significantly different surface morphologies were found on both types of films. Temperature dependent resistivity measurements of the films grown at 450°C on sapphire and glass show metal-like conductivity with electrical resistivity, ∼1.77×10−4 and ∼3.92×10−4Ωcm, respectively, at room temperature followed by either a residual conductivity or a metal-semiconductor transition at low temperature due to the localization effect caused by the defects.