High performance piezoelectric films for high frequency MEMS ultrasonic transducers

(1-x)PbYb₁2/Nb₁2/Nb₁2/O₃-xPbTiO₃ (PYbN-PT, x=0.5) thin films were investigated for high frequency transducer applications in this work. Firstly, highly [001] oriented LaNiO₃ (LNO) thin films were prepared on Si [001] substrates by a simple metal organic decomposition technique. The room temperature resistivity of the LNO thin films was 0.65 mΩ·cm. Then PYbN-PT thin films were deposited onto the LNO/Si substrates by sol-gel processing. X-ray diffraction analysis revealed that the films of PYbN-PT were highly [001] oriented along the LNO/Si substrates. The films had a uniform grain size of about 80-120 nm. At 1 kHz, the dielectric permittivity was 920, and dielectric loss is about 0.035. The ferroelectric films displayed good P-E hysteresis characteristics and better temperature stabilization compared with films that have lower Curie temperature. Finally, following PiezoCAD modeling, the PYbN-PT film high frequency transducer was designed.