A P(VDF-TrFE)-based integrated ultrasonic transducer

A thin film of a copolymer of vinylidene fluoride and trifluoroethylene, P(VDF-TrFE) has been deposited on top of the extended gate of an MOS transistor to make an integrated ultrasonic transducer. After spin deposition from solution onto a processed silicon wafer, the 2.5 μm thick copolymer film was locally corona-polarized to make it piezo- and pyroelectrically active. The piezoelectric and pyroelectric properties of the film have been evaluated over a frequency range of 3 Hz to 1 MHz. The response was found to be comparable with those of casted copolymer films.The ultrasonic response of the film backed by the transistor was verified in water at 10 MHz. An optimization scheme for the copolymer thin film and its interfacing transistor is presented.