Designing piezoelectric films for micro electromechanical systems

Abstract

Piezoelectric thin films are of increasing interest in low-voltage micro electromechanical systems for sensing, actuation, and energy harvesting. They also serve as model systems to study fundamental behavior in piezoelectrics. Next-generation technologies such as ultrasound pill cameras, flexible ultrasound arrays, and energy harvesting systems for unattended wireless sensors will all benefit from improvements in the piezoelectric properties of the films. This paper describes tailoring the composition, microstructure, orientation of thin films, and substrate choice to optimize the response. It is shown that increases in the grain size of lead-based perovskite films from 75 to 300 nm results in 40 and 20% increases in the permittivity and piezoelectric coefficients, respectively. This is accompanied by an increase in the nonlinearity in the response. Band excitation piezoresponse force microscopy was used to interrogate the nonlinearity locally. It was found that chemical solution-derived PbZr(0.52)Ti(0.48)O(3) thin films show clusters of larger nonlinear response embedded in a more weakly nonlinear matrix. The scale of the clusters significantly exceeds that of the grain size, suggesting that collective motion of many domain walls contributes to the observed Rayleigh behavior in these films. Finally, it is shown that it is possible to increase the energy-harvesting figure of merit through appropriate materials choice, strong imprint, and composite connectivity patterns.

{001} Oriented piezoelectric films prepared by chemical solution deposition on Ni foils

“…3 However, there are some applications for which flexible, high fracture toughness passive elastic layers would be desireable. 4 As one example, in MEMS energy harvesting devices, high density end masses enhance the output power efficiency and reduce the resonance frequency, but can introduce failure mechanisms if the passive layer is brittle. 5 Nevertheless, deposition of PZT films on base metal substrates, because of the thermodynamic incompatibility between PZT and the metal, is a challenge.…”

Dependence of e31,f on polar axis texture for tetragonal Pb(Zrx,Ti1−x)O3 thin films

“…This surpasses the FoM of PZT films grown on Si substrates by more than four times and is consistent with previous reports on the FoM of c-axis PZT. 22 It is also larger than the FoM of 0.6 C 2 /m 4 for scandium doped scandium aluminum nitride. 1 FIG.…”

“…films. 22 This shows that there is considerable room for improvement of the materials currently used in piezoelectric energy harvesting devices, such as AlN and {001}PZT/Pt/ SiO 2 /Si, which have FoM of 0.1 C 2 /m 4 and 0.2 C 2 /m 4 , respectively. 20 Additionally, epitaxial (110) PZT films on Si shown recently by Wan et al (2014) produced a FoM above 0.2 C 2 /m 4 using the polarization rotation effect.…”

A flexible, high-performance magnetoelectric heterostructure of (001) oriented Pb(Zr0.52Ti0.48)O3film grown on Ni foil

“…14 It is well known that the piezoelectric response of ceramics can be tailored by tuning their composition (via suitable stoichiometry and doping) and microstructural design (via grain and domain engineering). [16][17][18][19] Crystallographically oriented piezoelectric ceramic films have been shown to demonstrate better piezoelectric performance than their randomly oriented counterparts. [20][21][22][23] Although there have been some efforts to synthesize textured PZT films on magnetostrictive oxide substrates, which showed poor ME outputs, fabrication of ME composites with oriented PZT films on Ni has been rarely reported.…”