Design and Development of Sc_0.2Al_0.8N-Based Dual-Piezoelectric-Layer MEMS Hydrophone

Area of Science:

• Materials Science
• Acoustics Engineering
• MEMS Technology

Background:

• Microelectromechanical systems (MEMS) hydrophones are crucial for underwater acoustic sensing.
• Enhancing hydrophone sensitivity and frequency response is vital for improved detection capabilities.
• Scandium-doped aluminum nitride (ScAlN) shows promise for piezoelectric applications due to its enhanced properties.

Purpose of the Study:

• To present an innovative dual-piezoelectric-layer MEMS hydrophone design.
• To investigate the performance enhancement achieved through scandium doping and dual-layer structure.
• To evaluate the hydrophone's suitability for advanced underwater sensing and passive sonar systems.

Main Methods:

• Fabrication of a MEMS hydrophone utilizing a composite film of scandium-doped aluminum nitride (Sc$_{0.2}$Al$_{0.8}$N).
• Implementation of a dual-piezoelectric-layer design to broaden frequency response and increase sensitivity.
• Standard underwater acoustic calibration tests to measure sound pressure sensitivity, equivalent noise density, and linearity.

Main Results:

• The dual-piezoelectric-layer design significantly expanded the frequency response range and enhanced device sensitivity.
• Scandium doping notably increased the piezoelectric coefficient, further boosting sensitivity.
• The hydrophone achieved an average sound pressure sensitivity of -162 dB (re: 1 V/μPa) from 20 Hz to 50 KHz, with an equivalent noise density of 47 dB (re: 1 μPa/√Hz) and 99% linearity.

Conclusions:

• The developed dual-piezoelectric-layer MEMS hydrophone demonstrates superior comprehensive performance.
• This design offers a novel solution for underwater sensing and detection applications.
• The study opens new avenues for optimizing the performance of passive sonar systems through material and structural innovation.