Ultrasonic Transducers Employing ZnO-Film/Al-Foil Composite Structure and their Application to Acoustic Microscopes

抄録

The paper describes the development of ultrasonic transducers employing ZnO-film/Al-foil composite structure, and discusses their application to a scanning acoustic microscope (SAM) in VHF and UHF ranges.
It is theoretically shown that high performance ultrasonic transducers with low conversion loss and wide bandwidth can be realised by properly determining the thicknesses of the Al-foil and ZnO-film, and the effective diameter of the transducer.
The conversion loss of 6.7dB and -3dB bandwidth of 9.4% were experimentally achieved at the centre frequency of 142MHz, and the loss mechanism was discussed. A beam-focussing concave transducer was fabricated and applied to an SAM. SAM images revealed that the proposed transducers can be applied to various acoustic imaging systems.