Optical and electrical characterization of CuO/ZnO heterojunctions

CuO/ZnO p-n heterojunctions are fabricated on ZnO nanorod arrays by sputtering of metallic Cu thin films and by their subsequent thermal annealing at 400 °C. Structural, morphological, and optical properties of both copper oxide nanocrystalline films and zinc oxide nanorod arrays are discussed with the emphasis on the electrical junction properties investigated by current–voltage and impedance spectroscopy measurements. Electrical characteristics of these junctions are sensitive to gas mixtures with a low hydrogen concentration and show fast response and recovery time. The copper oxide/zinc oxide heterojunctions are shown to be more efficient to hydrogen detection at room temperature in comparison with the resistivity sensors based on zinc or copper oxides