Epitaxial PMnN-PZT/Si MEMS ultrasonic rangefinder with 2Â m range at 1Â V drive

In this study, we successfully developed a high signal-to-noise ratio (SNR) rangefinder based on a piezoelectric micromachined ultrasonic transducer (pMUT). A c-axis-oriented Pb(Mn1/3,Nb2/3)O3-Pb(Zr,Ti)O3 (PMnN-PZT) epitaxial thin film was employed as a piezoelectric transducer considering its outstanding figures-of-merit for SNR, due to the high piezoelectric coefficient and small relative permittivity (typical values: e31,f = −14C/m2, εr = 200-300). The pMUTs was based on an epitaxial PMnN-PZT/Si diaphragm structure and prototyped from a SOI substrate; its rangefinding ability was evaluated with a pair of devices, specifically, transmitter and receiver, respectively. As a result, the maximum range was estimated to be over 2 m at a low actuating voltage of 1 Vp-p, when 12 dB was set as the threshold SNR. The energy consumption of the transmitter was as small as ∼5 nJ for the generation of a 50-cycle ultrasonic burst. The noise analysis of the receiver's charge amplifier circuit indicated that this system could be improved by the optimization of bandwidth and by eliminating external noise. We believe that this high performance pMUT rangefinder will be utilized in various applications of consumer electronics or as an alternative to the bulk piezoelectric ceramic rangefinder in the near future.