Fabrication and calibration of nanostructured vanadium-doped ZnO-based micromachined sensor with superior sensitive for underwater acoustic measurement

A high-performance micromachined piezoelectric sensor based nanostructured vanadium-doped zinc oxide (ZnO) film with air-backing has been developed and characterized for underwater acoustic application. The sensing cell with a low foot-print of 2.0 mm x 2.0 mm is fabricated by Micro electro mechanical systems (MEMS) technology using a ZnO-on-silicon-on-insulator process platform. An optimal ratio of piezoelectric coefficient to the relative permittivity is obtained about 6.3 in the Zn0.98V0.02O sensing cell, improving by an order of magnitude compared with other notable piezoelectric films, plays a mainly dominant role in the enhanced piezoelectric response. Calibrations in the standard underwater instrument have demonstrated that the presented sensor could achieve an acoustic pressure sensitivity of -165 +/- 2 dB (1 V mu Pa-1) over a bandwidth 10 Hz-10 kHz, outperforming the same kind of reported devices. The maximum non-linearity is no more than 0.3%, the sensitivity variation is no more than +/- 0.7 dB in the temperature range from 10 degrees C to 50 degrees C, indicating a better stability and higher reliability. The proposed sensor with a superior acoustic sensitivity gives a great application potential in underwater acoustic measurements.