Effects of Domain Wall Movement Induced by Annealing on the Piezoelectric Property of ScAlN Thin Films

In this study, sputtered ScAlN thin films were annealed at different temperatures (300−700 °C) and in different atmospheres (nitrogen/oxygen), revealing the two key factors that affect piezoelectric performance after annealing: crystal quality and polarity distribution. The crystal quality of the ScAlN film is affected by the annealing temperature, while the polarity distribution is influenced by both the annealing temperature and atmosphere. Appropriate annealing temperature in a nitrogen atmosphere can improve film quality, repair defects, and promote domain wall movement, resulting in a uniform polarity distribution and thus a stronger piezoelectric response. Therefore, the piezoelectric coefficient d33 of ScAlN rises to 24.1 pm/V when annealed at 400 °C, 96% higher than the film before annealing. This study systematically investigates the effect of the annealing process on the polarity evolution of ScAlN thin films for the first time. It clarifies the intrinsic relationship between annealing and piezoelectric performance and provides a theoretical foundation for optimizing the annealing process of ScAlN material and its application in high-performance piezoelectric devices.