Electrical and reducing gas sensing properties of ZnO and ZnO-CuO thin films fabricated by spin coating method

Abstract

ZnO and ZnO-CuO composite thin films were fabricated by sol-gel spin coating method and their electrical conductivities and the reducing gas sensitivities were measured between 100 and 500 degrees C. As the thickness of ZnO film linearly increased with the repeated coating, the grain size increased and the film became denser. As a result, the electrical conductivity increased. CuO addition is shown to increase the grain size of ZnO-CuO composite film. As the number of coating increased, the thickness of ZnO-CuO film also increased together with the grain size. The electrical conductivity increase was also observed for ZnO-CuO film with repeated coatings. The 10 mol.% CuO addition eliminated the CO gas sensitivity of the him and severely reduced H-2 gas sensitivity. The co-addition of CuO and Al2O3 gave effects of contribution of p-type conduction on the reducing gas sensitivity of ZnO film. (C) 1999 Elsevier Science S.A. All rights reserved.