Fabrication of Microcantilever Sensors Actuated by Piezoelectric Pb(Zr_0.52Ti_0.48)O₃ Thick Films and Determination of Their Electromechanical Characteristics

Abstract

The integration and the device realization of Pb(Zr, Ti)O3 (PZT) thick films on Si substrates are known to be extremely difficult because the processing temperature of the PZT thick film is close to the melting point of Si. However, PZT thick‐film devices on Si warrant attention as they are appropriate for biological transducers; they generate large actuating forces and have a relatively high sensitivity for mass detection, especially in liquids. In this study, Pb(Zr0.52Ti0.48)O3 thick‐film cantilever devices are successfully fabricated on a Pt/TiO2/SiNx/Si substrate using a screen‐printing method and microelectromechanical systems (MEMS) process. Elastic and electromechanical properties such as the Young's modulus and transverse piezoelectric coefficient are determined from microstructural and electrical analyses for further mechanical study. The calculated Young's modulus of the thick film, 53.9 ± 3.85 GPa, corresponds to the resonant frequency obtained from the measured harmonic oscillation response. The transverse piezoelectric constant, d31, of –20.7 to –18.8 pC N–1 is comparable to that of a dense thin film. These values promise the possibility of determining the resonance properties of a thick‐film cantilever by designing its structure and then simulating the harmonic oscillation response. Using the PZT thick‐film cantilever, a strong harmonic oscillation with a quality (Q) factor of about 23 is demonstrated in water. The observation of strong harmonic oscillation in liquid implies the feasibility of precise real‐time recognition of biomolecules using PZT thick‐film cantilevers.

Nanomechanical resonators and their applications in biological/chemical detection: Nanomechanics principles

“…a 0.1Pb(Zn 0.5 W 0.5 )O 3 -0.9Pb(Zr 0.5 Ti 0.5 )O 3 (PZW-PZT) thick film, that allows the actuation of micro devices with large actuation forces. Using this PZW-PZT thick film, they developed a piezoelectric unimorph microcantilever that can vibrate with large actuation forces even in a viscous medium [79]. The resonance behavior of the piezoelectric unimorph microcantilever is well described by classical linear elastic Euler-Bernoulli beam theory.…”

“…Here, in situ detection of proteins in solution is of high significance, because in situ detection allows the real-time monitoring of protein-protein interactions, which will enable novel insights into the kinetics of protein-protein interactions. Recently, Kwon and coworkers [22,23] utilized a piezoelectric thick film microcantilever [79], which exhibits a relatively high Q-factor even in a viscous liquid, for the real-time monitoring of biomolecular interactions. In their work [22,23], it is shown that the frequency shift due to biomolecular interactions on the cantilever surface is governed by not only the mass of target biomolecules but also the hydrodynamic loading change driven by hydrophilicity change during the biomolecular interactions (see Fig.…”

“…The resonance behavior of the piezoelectric unimorph microcantilever is well described by classical linear elastic Euler-Bernoulli beam theory. Specifically, the flexural rigidity for the microcantilever composed of two layers is given as [79,80] …”

Effects of the material properties on piezoelectric PZT thick film micro cantilevers as sensors and self actuators

“…Nonetheless, the resonance and sensing properties of PZT thick film cantilever devices using resonance behavior have rarely been studied before, because not only the processing temperature of the PZT thick film is high enough to generate PbO condensation and reaction to undesirable glassy phase, but also micro-patterning using the etching process of PZT thick film is not easy or desirable [1][2][3][4][5][6][7][8][9].…”

Epitaxial perovskite oxide devices fabricated by lift-off technology

“…Polycrystalline PZT suffers several key disadvantages over epitaxial PZT, including higher leakage current, lower piezoelectric coefficients and inferior ferroelectric properties [52][53][54][55]. Moreover thicker PZT films need very high electrical voltages for piezoelectric actuation which is a major problem in their integration with electronic read-out circuits [53,56]. Hence in order to be compatible with Si-based very large scale integration (VLSI) technology, thinner PZT films (requiring moderate actuation voltages) are essential while maintaining superior piezo and ferroelectric properties and epitaxial films are ideal candidate to serve this purpose.…”