Wideband Multimode Transducer Consisting of c-Axis Tilted ZnO/c-Axis Normal ZnO Multilayer

Abstract

Wideband ultrasonic transducers are required for acoustic imaging and nondestructive evaluation. In this study, we have fabricated transducer consisting of c-axis tilted ZnO/c-axis normal ZnO multilayer on the Au(111)/Ti/silica glass substrate. We have investigated the crystalline orientations and frequency characteristics of the multilayer transducer. An X-ray diffraction analysis and a scanning electron microscopy analysis of the transducer revealed that the c-axis normal ZnO layer was grown on the Au(111) layer during the initial stage of ZnO layer deposition. As ZnO grain growth proceeded, c-axis normal growth change to the c-axis tilted ZnO layer growth. This multilayer transducer excited secondovertone modes of longitudinal and shear waves as well as the fundamental mode in the UHF range. Therefore, the frequency bandwidth of the multilayer transducer was broader than that of a single layer transducer consisting of a c-axis tilted ZnO layer.

Evaluation of Piezoelectric Ta2O5 Thin Films Deposited on Sapphire Substrates

“…Piezoelectric thin films with high coupling, high stability, low loss, and high phase velocity are required for the development of high-performance piezoelectric devices, such as surface acoustic wave (SAW) and film bulk acoustic resonator (FBAR) devices. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] An X-axis-oriented Ta 2 O 5 piezoelectric thin film is a relatively new material developed by Nakagawa and coworkers and has a strong piezoelectric property similar to that of ZnO thin films and a high dielectric constant. [16][17][18][19][20][21][22] In the deposition of X-axis-oriented Ta 2 O 5 piezoelectric thin films using an RF magnetron sputtering system with a long-throw sputter (LTS) cathode, Kakio, one of the authors, and colleagues found the optimum deposition conditions for obtaining a strong preferential (200) orientation and a high electromechanical coupling factor K 2 for a Rayleigh-type SAW (R-SAW) on synthetic fused silica (SiO 2 ) glass substrates, 23) and demonstrated the application of the optimum deposition conditions to the fabrication of an FBAR with a Si substrate.…”

Engineering inclined orientations of piezoelectric films for integrated acoustofluidics and lab-on-a-chip operated in liquid environments

“…(1) Non-uniformity of film thickness and inclination or tilting angles over a large planar scale. As mentioned, most of the methods used to generate the inclination angle are not able to obtain a significant uniformity over large areas (for example, larger than 2 or 3 inches) 125 ;…”

100-MHz ultrasonic linear array transducers based on polyurea-film

“…Several different transducer materials are being investigated for use in high-frequency ultrasound imaging. These include lead zirconate titanate (PZT) [4][5][6][7][8], piezoelectric polymers such as polyvinylidene fluoride (PVDF) [9][10][11], capacitive micromachined transducers (cMUTs) [12], and zinc oxide (ZnO) [13]. Piezoelectric polymers have drawn considerable attention as materials for advanced transducers [14][15][16][17].…”