A vibration analysis of an acoustic mass sensor structure with a c-axis tilted ZnO thin film based on silicon

A theoretical study was conducted on the free vibration and forced vibration behaviors of a piezoelectric bulk acoustic mass sensor featuring a c-axis tilted ZnO thin film on silicon using piezoelectric elasticity theory. The purpose is to establish the relationship between c-axis inclination angle and sensor performance. It operates in either thickness-extensional mode or thickness-shear mode. The inclination angle of the c-axis is intricately connected to the operating modes, frequency characteristics, and output admittance spectrum. Key results show: (1) Characteristic distributions of extensional and shear displacements across the thickness, and (2) Numerical simulations revealing distinct admittance spectrum patterns for different angles. Furthermore, mass-loading effects on resonant frequency shifts were quantified across different inclination angles. In conclusion, strategic control of the c-axis tilt angle enables precise optimization of resonant modes and mass sensitivity-critically motivated by the need for tunable high-sensitivity sensors in biochemical detection-providing critical design guidelines for enhanced acoustic sensors.