FABRICATION OF A CUO-INFILTRATED ZNO COMPOSITE AND ITS GAS-SENSING PROPERTIES

CuO-ZnO composites were fabricated by heating with infiltrating a cupr ic solution into a porous ZnO matrix. The composites possess a nonline ar, rectifying current-voltage character due to the presence of a p-n junction produced by the CuO and ZnO semiconductors. This junction is essential for the creation of voltage-dependent sensing properties of humidity and flammable gases. The forward current (CuO: positive bias) greatly increased with increasing the relative humidity, while the re verse current only slightly increased with an equivalent increase in t he relative humidity. This asymmetric current change with the humidity is similar to that observed for conventional CuO and ZnO sintered spe cimens heterocontact produced by mechanically pressing the specimens t ogether. The current was increased by the introduction of CO and H-2 ( 4000 p.p.m.) at 250 degrees C, with the current increase due to CO exc eeding that of the H-2 in the measured bias region within +/-6 V. The utility of the new processing method for forming p-n semiconductor jun ctions open to the atmosphere has been shown.