Electrical properties of lead-free (K0.5Na0.5)NbO3 piezoelectric thin films

Abstract

Due to rising environmental issues on lead usage in microelectronic material, a promising alternative, sodium potassium niobate (KNN) piezoelectric ceramic has been investigated to replace the market dominant lead zinc titanate (PZT) piezoelectric ceramic. However, persistent problems of KNN show that its electrical properties are still unable to compete with PZT. In this report, various electrical properties of KNN thin films have been studied with different thicknesses, including dielectric, ferroelectric, piezoelectric and leakage current. Results showed that the dielectric and ferroelectric properties were generally improved with increased thickness due to the reduced impact of interface effect. Also, the films annealed at 7000C showed better results than the films annealed at 5800C because of reduced space charges and leakages. On the other hand, piezoelectric property did not show favourable increment with increasing film thickness. A suspect of surface cracks caused by striation may be the determining factor that caused d33 value to decrease with increased film thickness. These findings will be considered for improving surface morphology and property of KNN thin film for the future work.