Effects of annealing dwell time on piezoelectric properties of KNN thin films: Phase insensitive behavior

Amorphous potassium sodium niobate (KNN) thin films were deposited onto Pt/Ti/SiO 2 /Si substrates at 200°C using magnetron sputtering. The resultant films were then annealed in an alkali metal element atmosphere formed by alkali metal carbonates. The influence of annealing dwell time on the films' properties was investigated. It was observed that while the overall crystalline phase and elemental composition of the films remained essentially unchanged, their electrical characteristics exhibited systematic variations. Microscopic analysis revealed that extending the annealing time within an optimal range facilitated the formation of ferroelectric domain structures and enhanced piezoresponse phase contrast between domains. However, prolonged annealing led to localized phase segregation, resulting in performance degradation. Our results provide useful insights into the fabrication of KNN thin films using magnetron sputtering or other thermally involved synthesis methods.