Sensitivity of Micro Cantilever Mass Sensor Transduced by PZT Film

Piezoelectric thin film transduced micro resonator offers competitive potential applications in mass sensing technology because of its low driving-voltage, self-actuation self-sensation capability and better impedance-matching with electronics. In this paper, the authors fabricated PZT cantilevers with different geometries and PZT thicknesses. Then the authors investigated the essential aspects of the PZT cantilever for mass-detection sensitivity from the viewpoint of mechanical quality factor of the cantilever and piezoelectric induced output of the PZT film. It was found that the mass-detection sensitivity of the cantilever was improved at thicker PZT film under atmospheric conditions by taking advantage of quality factor. The sensitivity can be further improved several times when pressure was reduced into the molecular flow region and the intrinsic region. For a given material properties and structural layer thickness, the cantilever with thicker PZT film was expected to exhibit high open circuit voltage output, while the cantilever with thinner PZT film was expected to show high piezoelectric charge output. In addition, the residual stress of PZT film was found decreased at thicker film. The effects of residual stress in PZT film on cantilever's sensitivity were therefore discussed in this paper.

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