Study on gas sensing mechanism in p-CuO/n-ZnO heterojunction sensor

Abstract This work describes the need of more reactive sites for gas sensing. The formation of heterojunctions may increase the number of reactive sites. With this aim, ZnO:CuO nanoparticles with heterojunction was synthesized by co-precipitation method. XRD measurements on ZnO and ZnO:CuO (90:10) nanoparticles revealed the hexagonal wurtzite structure of ZnO with the signature of CuO phases in ZnO:CuO nanoparticles. The morphological analysis by SEM and TEM showed that the nanoparticles are arranged in such a way to form distorted rod-like structures, which are stacked side by side to give a chunk-shaped morphology. High resolution TEM and Fourier transform infrared analyses revealed the presence of defects in the sample. ZnO:CuO nanoparticles showed high sensitivity toward ethanol, which is associated with the introduction of large number of reactive sites and the formation of heterojunctions with the addition of CuO. The sensing mechanism behind the sensing materials is also proposed using energy band diagrams.