Fabrication and characterization of a smart epitaxial piezoelectric micromachined ultrasonic transducer

Highlights: • Highly [1 1 1] orientated functional PZT(1 1 1) thin film was grown on n-Si(1 1 1)/γ-Al₂O₃(1 1 1)/SrRuO₃(1 1 1). • Device performance of pMUT was studied using both experiment and modeling. • Material anisotropy played a significant role in the shifting of resonant frequency • pMUT shows high sensitivity for the transmission of ultrasonic pulses. • Successful realization of a piezoelectric ultrasonic transducer (pMUT) array. - Abstract: A novel piezoelectric micromachined ultrasonic transducer (pMUT) array was designed and fabricated using epitaxially grown functional Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin film on Si(1 1 1)/γ-Al₂O₃(1 1 1)/SrRuO₃(1 1 1) substrate for biomedical applications. The crystallographic orientation of PZT film was controlled by the incorporation of epitaxial γ-Al₂O₃ film on Si substrate. Modal shape of pMUT was analyzed employing advanced 3D finite element modeling taking the crystallographic anisotropy of materials and the properties of immersed medium (air or water) into account. Eigenfrequency with mode shapes has shown to have significant influence on transmitting-receiving characteristics of pMUT. Modal shapes of pMUT were also quantitatively determined using Laser Doppler Vibratometry (LDV). An excellent correlation was obtained between computational and experimental results. A significantly high sensitivity of 3.9 μV/kPa was obtained in an under-water ultrasonic wave transmission experiment conducted using fabricated pMUT as wave transmitter and a commercial transducer as receiver at a fundamental frequency of 1.20 MHz. Advanced FE computation thus serves as a tool to a priori optimize device structure for the successful transmission of ultrasonic waves with sufficient power to generate high resolution 3D imaging