Ultrasonic properties of PZT thin films in UHF-SHF ranges-prepared by sol gel method

A study of piezoelectric and ultrasonic properties was carried out for PZT films of 0.22 to 2.65 μm thickness prepared by the sol gel method. First, bulk wave transducers were fabricated employing the PZT films deposited on a Si substrate, and their transducer performances based on thickness-longitudinal vibration were measured. Ultrasonic pulse echo trains were clearly observed with the bias voltage of 30 V. The minimum conversion loss reached 3.8 dB at 1.75 GHz. Next, an SAW delay line employing the PZT film was fabricated on a sapphire substrate. With the bias voltage of 30 V, the responses which may be attributed to SAWs were observed. The possibility of developing SAW devices on Si substrates was also experimentally discussed. Finally, a simple bulk wave PZT film/Si diaphragm resonator was fabricated by anisotropic etching of Si substrates, and the anti-resonance Q factor of about 84 was obtained at 1.7 GHz