| 研究開始時の研究の概要 |
The purpose of this research is to create an innovative piezoelectric micromachined ultrasonic transducer (pMUT) that integrates the best materials for the transmitter and the best material for the receiver. The AlN material and Sm-PMN-PT material will be integrated on one Si wafer to create a pMUT device, this pMUT device is supposed to achieve much higher performance than the existing single piezoelectric layer pMUT devices and bulk type transducers. Finally, the single pMUT is supposed to be integrated in pMUT array for better performance.
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| 研究実績の概要 |
1. Dual layer pMUTs with AlN on PMN-PT and PZT on AlN were prototyped. A resonant frequency around 265 kHz and 203 kHz is confirmed for AlN/PMN-PT and PZT/AlN pMUT, respectively. The AlN/PMN-PT pMUT has a displacement sensitivity of 3538 nm/V and 306 nm/V when actuating the PMN-PT and AlN layer, respectively. The PZT/AlN pMUT has a displacement sensitivity of 1036 nm/V and 744 nm/V when actuating the PZT layer and the AlN layer, respectively.
2. The concept of using different piezoelectric materials for transmission and reception separately was verified. The actuation voltage was applied to the transmitting layer while the sensed voltage was measured for the receiving layer. The electrical conversion coefficient was defined as the ratio of the voltage applied to the transmission layer to the voltage generated on the reception layer. The coefficient was about 0.256 and 0.039 for AlN/PMN-PT and PZT/AlN pMUTs, respectively.
3. The transmitting and receiving figure of merit (FOM) were compared with the conventional single piezo layer pMUT. No-patterned AlN/PMN-PT pMUT exhibited a 1.3 times higher value than the patterned conventional PZT single-layer pMUT.
4. The optimization of the pMUT was simulated for higher performance. The dimension of the electrodes, and piezoelectric layer was simulated. The optimized results showed 1.25 times higher than the prototyped one. Meanwhile, the thicknesses of the piezoelectric layer were also simulated. With optimized thickness, the pMUTs could exhibit 2 times higher value than the prototyped one.
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