Giant piezoelectric response and electromechanical coupling in AlScN thin films via multi-scale lattice engineering.

High-performance AlScN thin films are critical for next-generation lead-free piezoelectric applications. Here, giant electromechanical coupling and piezoelectric response are demonstrated in Al0.9Sc0.1N thin films via a multi-scale lattice engineering strategy. Post-growth rapid thermal annealing significantly boosts the piezoelectric coefficient to 15.0 pC N-1 and electromechanical coupling to 34.9%. This performance enhancement stems from a synergistic mechanism: a reduced c/a lattice ratio and homogenized nanodomain alignment, fundamentally underpinned by a transition toward higher bond ionicity as evidenced by reduced minimum electron density at the bond saddle points. Leveraging an industrial-grade 6-inch wafer process, the prepared MEMS chip exhibits tailored electromechanical characteristics and a resonant frequency of 368.2 kHz. The optimized piezoelectric response enables record-breaking acoustic sensitivity of -162.4 dB at 10 Hz and a noise floor of 59 dB at 1 kHz, with robust stability across diverse media and temperatures up to 150 °C. This work provides a scalable, mechanism-driven pathway for tailoring the electromechanical properties of AlScN thin films, addressing the long-standing challenge of high-fidelity weak signal detection in extreme environments.