title: c-Axis zig-zag ZnO film ultrasonic transducers for designing longitudinal and shear wave resonant frequencies and modes.
abstract: A method for designing frequencies and modes in ultrasonic transducers above the very-high-frequency (VHF) range is required for ultrasonic non-destructive evaluation and acoustic mass sensors. To obtain the desired longitudinal and shear wave conversion loss characteristics in the transducer, we propose the use of a c-axis zig-zag structure consisting of multilayered c-axis 23° tilted ZnO piezoelectric films. In this structure, every layer has the same thickness, and the c-axis tilt directions in odd and even layers are symmetric with respect to the film surface normal. c-axis zig-zag crystal growth was achieved by using a SiO(2) low-temperature buffer layer. The frequency characteristics of the multilayered transducer were predicted using a transmission line model based on Mason's equivalent circuit. We experimentally demonstrated two types of transducers: those exciting longitudinal and shear waves simultaneously at the same frequency, and those exciting shear waves with suppressed longitudinal waves.
authors.affiliation: Graduate School of Engineering, Nagoya Institute of Technology, Nagoya, Japan. yana@nitech.ac.jp
authors.forename: Takahiko
authors.initials: T
authors.lastname: Yanagitani
authors.forename: Naoki
authors.initials: N
authors.lastname: Morisato
authors.forename: Shinji
authors.initials: S
authors.lastname: Takayanagi
authors.forename: Mami
authors.initials: M
authors.lastname: Matsukawa
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Watanabe