Effect of preheating and annealing temperatures on quality characteristics of ZnO thin film prepared by sol–gel method

In order to fabricate qualified ZnO piezoelectric thin films by sol–gel method, the relationships between the heat treatment temperatures (preheating temperature and annealing temperature) and the quality characteristics of ZnO piezoelectric thin films (c-axis orientation, residual stress, grain size, roughness and resistivity) were investigated. The chemical composition of the precursor sol and the intermediate produced in the films heating process were analyzed by TGA–SDTA and FT-IR. The c-axis orientation and the residual stress of the ZnO thin film were identified by XRD. The morphologies, roughness and grain size were observed and estimated by AFM. The I–V characteristics were measured by using semiconductor characterization system. Experimental results show that the c-axis orientation is determined by both preheating and annealing temperatures, and that the residual stress, grain size, roughness and resistance of the ZnO thin films are mainly influenced by the annealing temperature. A qualified ZnO piezoelectric thin film has been prepared by using sol–gel with preheating temperature 400 °C for 10 min and annealing temperature 700 °C for 30 min.