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 × 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 Zn 0.98 V 0.02 O 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 μ 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 °C to 50 °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.