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

• Published in: Micromachines (Basel) Vol. 9; no. 9; p. 455
• Main Authors: Ngoc Thao, Pham, Yoshida, Shinya, Tanaka, Shuji
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 11-09-2018; MDPI
• Subjects: Deoxidizing; epitaxial thin film; Epitaxy; Grain boundaries; Lead zirconate titanates; Microelectromechanical systems; micromachined ultrasound transducer (pMUT); Micromachining; Organic chemicals; Photovoltaic cells; piezoelectric materials; Piezoelectricity; Polycrystals; Scanning electron microscopy; Sensors; Thin films; Ultrasonic imaging; Ultrasonic transducers; X-ray diffraction; United States > US; piezoelectric materials; epitaxial thin film; micromachined ultrasound transducer (pMUT)
• ISSN: 2072-666X; 2072-666X
• DOI: 10.3390/mi9090455

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 (
= 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
= -10⁻-11 C/m², and thus reasonably high compared to polycrystalline thin films. An appropriate poling treatment increased
and decreased
. 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.