High sensitivity ultrasonic sensor for hydrophone applications, using an epitaxial Pb(Zr,Ti)O3 film grown on SrRuO3/Pt/γ-Al2O3/Si

A piezoelectric ultrasonic sensor has been fabricated using an epitaxial lead zirconate titanate, Pb(Zrx, Ti1−x)O3 (PZT) thin film, grown on an epitaxial SrRuO3/Pt/γ-Al2O3/Si substrate. The 3-μm thick PZT film was prepared by the sol–gel method. This sensor structure was very stable during the fabrication process after preparation of the PZT. The fabricated sensor offers a reception sensitivity of up to −243 dB re 1 V/μPa in the frequency range from 1 to 15 MHz, which means that it has higher sensitivity than that of a conventional polyvinylidene fluoride (PVDF) hydrophone. The pressure field of a focused ultrasonic transducer was determined using this ultrasonic sensor. The measured pressure peak was in good agreement with the results derived from calculations. These results suggest that the fabricated ultrasonic sensor can be used as a high sensitivity hydrophone device.