Photoconductive properties of ZnO thin films grown by pulsed laser deposition

The photoconductive properties of ZnO thin films grown by pulsed laser deposition are presented. The conductivity of ZnO films was measured based on metal-semiconductor-metal planar structures. Dark conductivity transients were measured with an electric field applied, and a change of up to more than three orders of magnitude was observed. The film shows a slow photoresponse with a rise time of 6 min and a decay time of several hours. Dark conductivity and photoconductivity transients indicate that the increase/decrease of the conductivity may be attributed to the adsorption/desorption of oxygen on the surface and the grain boundaries.