Characterization and ammonia sensing properties of pure and modified ZnO films

Abstract

Zinc oxide (ZnO) films have been prepared by thermal oxidation of pre-deposited zinc films on the glass substrate kept at room temperature. These films were surface modified by dipping them into an aqueous solution (0.1 M) of lithium chloride (LiCl) and aluminium chloride (AlCl3) followed by firing at 500°C. Based on X-ray diffraction results it is observed that modification of pure ZnO by lithium and aluminium precursor results a change in the lattice parameters. Li and Al ions appear to enhance the a-axis orientation and c-axis orientation of pure ZnO films, respectively. Field emission scanning electron micrographs of lithium-modified ZnO film indicate the presence of nanoneedles, while nanorods are observed in case of aluminium-modified ZnO film. The electrical resistance measurements of modified ZnO films also show variation in resistance as compared to pure ZnO film. Pure and Al-modified films of ZnO are sensitive to ammonia at room temperature, while Al-modified ZnO film is found to be more sensitive with 99% of response at 250 ppm.