Piezoelectric and Electrothermal Driven Tunable Mode Localized Coupled Silicon Carbide Resonators

This study reports the first successful fabrication and characterization of mode localized mechanically coupled resonators based on silicon carbide (SiC). Due to SiC’s high Young’s modulus, SiC-based resonators achieve higher frequencies than traditional silicon-based devices of the same dimensions. The system was designed, simulated, and fabricated with integrated aluminium nitride (AlN) films and electrothermal electrodes to enable dual-mode actuation and frequency tuning. The piezoelectric AlN thin film was deposited by DC sputtering and subsequently characterized by X-ray diffraction (XRD) and piezoresponse force microscopy (PFM). The piezoelectric coefficient $d_{33}$ was measured to be 1.6 pm/N. X-ray photoelectron spectroscopy (XPS) revealed an Al:N ratio of 1.12:1 with minor oxygen impurities. The resonant frequency and amplitude of the coupled resonators were measured using a laser Doppler vibrometer (LDV). Compared to electrothermal actuation, the system under piezoelectric actuation exhibited a more linear, stable, and larger-amplitude response, resulting in a quality factor of 197. The introduction of electrothermal tuning allows the system to be balanced, compensating for fabrication tolerance and environmental effects. When a 2 V DC voltage is applied to the electrothermal port, the resulting thermal stress change induces a change of amplitude ratio of 225%, which is 52.4 times higher than the resonant frequency change. This study provides a foundation for the future use of SiC in mechanically coupled resonators as actuators or sensors.[2025-0058]