ScAlN thick film ultrasonic transducer in 40 MHz–80 MHz

Ko hei Sano, Rei Karasawa, Takahiko Yanagitani

    Research output: Contribution to journalArticlepeer-review

    7 Citations (Scopus)

    Abstract

    A medical ultrasound diagnostic system and an ultrasonic microscope are generally used in the frequency range of 1 MHz – 20 MHz and 100 MHz – 2 GHz, respectively. Ultrasonic transducers in the frequency range of 20 MHz – 100 MHz are, therefore, not well-developed because of less applications into ultrasonic imaging or suitable piezoelectric materials with this frequency range. PVDF are usually used for ultrasonic transducers in the 10 MHz – 50 MHz ranges. However, their electromechanical coupling coefficient kt 2 of 4% is not enough for the practical uses. In order to excite ultrasonic wave in the 20 MHz – 100 MHz, 125μm – 25μm thick piezoelectric film is required when the longitudinal velocity of material is assumed to be 5000 m/s. However, it is difficult to grow such a thick piezoelectric film without a crack being caused by the internal stress during the dry deposition technique. We achieved stress free film growth by employing the unique hot target sputtering technique without heating substrate. High efficient 81 MHz (kt 2=18.5%) and 43 MHz (kt 2=15.2%) ultrasonic generation by using the 43 m and 90 m extremely thick ScAlN (Sc:39%) films were demonstrated, respectively. We discussed the advantage of ScAlN thick film transducers by comparing them with conventional PVDF transducer for water medium.

    Original languageEnglish
    JournalIEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
    DOIs
    Publication statusAccepted/In press - 2018 Aug 23

    Keywords

    • Acoustics
    • Frequency control
    • Piezoelectric films
    • Piezoelectric films
    • Piezoelectric resonators
    • ScAlN
    • Sputtering
    • Substrates
    • Thick films
    • thick piezoelectric film
    • Transducers
    • ultrasonic transducer
    • Ultrasonic transducers

    ASJC Scopus subject areas

    • Instrumentation
    • Acoustics and Ultrasonics
    • Electrical and Electronic Engineering

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