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

Abstract

Our research, based on executing theoretical modeling depending on the dimensions of PZT (lead zirconate titanate) thin film, was applied to two different bridge-shaped 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 XeF2 gas, while the second type of bridge-shaped resonator is released by a wet etching method that uses a KOH solution. The bridge-shaped 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 mu m x 250 mu m, 100 mu m x 500 mu m, and 150 mu m x 750 mu m, 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 mu m x 250 mu m, 100 mu m x 500 mu m, and 150 mu m x 750 mu m were 2.02 Hz/pg, 330.42 Hz/ng, and 43.67 Hz/ng, respectively. Thus, the bridge-shaped resonator with dimensions of 50 mu m x 250 mu m was able to detect the picogram-level of a mass.