Generation and detection of ultrasonic Lamb waves in a thin deposited film by using interdigital transducers

Abstract

Interdigital transducers (IDT’s) have been used to generate and detect ultrasonic Lamb waves in a composite Cu(3 μm)-ZnO (0.45 μm) film that is much thinner than the acoustic wavelength in a bulk material. rf pulses of 29.0 and 1.31 MHz are applied to one of the pair of IDT’s with 140-μm period, giving rise to a nondispersive quasi-symmetric mode of phase velocity 4170 m/s and a dispersive quasi-antisymmetric mode having a phase velocity of 184 m/s and a group velocity of 362 m/s, respectively. Possible applications to electronic signal processing and material studies are described.