A Si-monolithic ultrasonic sensor has been developed by sputtering of PbTiO3 thin film on a micro-membrane cantilever on a Si wafer. This device has a dimension of several tens to several hundred microns in length and a few tens to a few hundred microns in width. Its ultrasonic response in the frequency region up to 150 kHz has been confirmed. A series of technical data on resonant frequency, sensitivity and quality factors are presented with some design parameters such as the kind of film and size. Typical sensitivity and quality factors are -102 dB and 290 at 35 kHz, respectively. This three element linear array sensor shows sharper directivity than that with a single element.

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