Growth of highly c-axis oriented ZnO thin films by spray pyrolysis for piezoelectric applications

Abstract

In this work, the piezoelectric response in ZnO thin films deposited by ultrasonic spray pyrolysis (USP) technique with a preferential orientation at the c-axis was explored. The films were fully characterized by X-ray diffraction (XRD), photoluminescence (PL), atomic force microscopy (AFM), and ellipsometry, respectively. The results showed an increase in the crystalline film quality and grain size at higher temperatures. Besides, the angular distribution of the crystals at the plane (002) was obtained from the pole figures in XRD and they have shown a small deviation from the normal of the substrate plane at higher temperatures. Afterwards, to measure the piezoelectric response, a prototype based on ZnO thin films deposited on silicon cantilevers was fabricated. A mechanical deformation was produced by hitting the cantilever with a metallic pellet falling at a constant height. In this way, the piezoelectric response was observed and measured, results have indicated that samples with better crystallinity and high resistivity have shown the most intense measured piezoelectric voltage.