Fabrication and characterization of PZT (lead zirconate titanate) bridge-shaped resonator for mass sensing application

Our research, based on executing theoretical modeling depending on the dimensions of PZT (lead zirconate titanate) thin film, was applied to two different bridgeshaped resonators. The critical point of having two different types of resonators is that it is a way of releasing the bridge. The first type of bridge-shaped resonator is released through use of an isotropic etching method using XeF ₂ gas, while the second type of bridge-shaped resonator is released by a wet etching method that uses a KOH solution. The bridgeshaped resonators are anticipated to have accurate mass detecting sensors based on high mass sensitivity compared to the other shapes, such as diaphragms and cantilevers. The feasibility of a bridge-shaped PZT resonator as a mass sensor has been researched through studying the resonant frequency shift of a bridge-shaped resonator. The actual resonant properties of bridge-shaped resonators were determined by measuring resonant frequency and Q-factor measurements using an LDV (Laser Doppler Vibrometer). The resonant frequency appears in the ranges of 378.4-419.8, 144.0-180.3, and 107.8-123.4 kHz for dimensions of 50 μm̃250 μm, 100 μm̃500 μm, and 150 μm̃750 μm, respectively. Finally, four different thicknesses of Titanium (Ti) were loaded on the bridge-shaped resonator to confirm its variation and mass sensitivity. Significantly, mass sensitivities with dimensions of 50 μm̃250 μm, 100 μm̃500 μm, and 150 μm̃750 μm were 2.02 Hz/pg, 330.42 Hz/ng, and 43.67 Hz/ng, respectively. Thus, the bridge-shaped resonator with dimensions of 50 μm̃250 μm was able to detect the picogram-level of a mass.