Fabrication and Characterization of PZT Fibered-Epitaxial Thin Film on Si for Piezoelectric Micromachined Ultrasound Transducer

Abstract

This paper presents a fibered-epitaxial lead zirconate titanate (PZT) thin film with intermediate features between the monocrystalline and polycrystalline thin films for piezoelectric micromachined ultrasound transducer (pMUT). The grain boundaries confirmed by scanning electron microscopy, but it still maintained the in-plane epitaxial relationship found by X-ray diffraction analyses. The dielectric constant (εr33 = 500) was relatively high compared to those of the monocrystalline thin films, but was lower than those of conventional polycrystalline thin films near the morphotropic phase boundary composition. The fundamental characterizations were evaluated through the operation tests of the prototyped pMUT with the fibered-epitaxial thin film. As a result, its piezoelectric coefficient without poling treatment was estimated to be e31,f = −10–−11 C/m2, and thus reasonably high compared to polycrystalline thin films. An appropriate poling treatment increased e31,f and decreased εr33. In addition, this unique film was demonstrated to be mechanically tougher than the monocrystalline thin film. It has the potential ability to become a well-balanced piezoelectric film with both high signal-to-noise ratio and mechanical toughness for pMUT.

Review of pMUTs for medical imaging: towards high frequency arrays

“…Thao et al in 2018 replaced monocrystalline/polycrystalline PZT with fibered-epitaxial PZT to improve piezoelectric properties of PZT thin-films used in pMUT fabrication, the reported results were promising in terms of offering more design flexibility and improved signal-to-noise ratio for the pMUT's [51].…”

Design and fabrication strategy for an efficient lead zirconate titanate based piezoelectric micromachined ultrasound transducer

“…Architecture (c), in which the PZT layer is patterned on top of the membrane, is an improved version of the one that was used by Thao et al [24]. Unlike the work of Thao et al, we could successfully pattern the PZT without any crack or delamination of the PZT layer.…”

Review of Piezoelectric Micromachined Ultrasonic Transducers for Rangefinders

“…Therefore, the product of the sensitivities can be described by , which is denoted as the figure of merit for a pMUT [ 80 ]. Since larger give rise to a smaller maximum range error or larger maximum range according to Equation (10), researchers have been working on choosing different piezoelectric materials and strategies to enhance by increasing the absolute value of or decreasing in order to enlarge the maximum range of pMUT rangefinders [ 81 , 82 , 83 ].…”