Significant Enhancement in Operational Bandwidth of ZnO PMUTs due to the Simultaneous Existence of Softening and Hardening Nonlinearity

This paper reports the first experimental observation of mixed nonlinearity (softening followed by hardening) in ZnO based PMUTs and their exploitation for enhancing the bandwidth of the transducer. These experiments are conducted on PMUTs fabricated with nanostructured ZnO thin film as the active piezoelectric material. The mixed nonlinearities in peak response are observed at relatively low actuation voltage of 1–6 V AC. We show that the intrinsic jump phenomenon embedded in this kind of nonlinear response can be effectively used to enhance the operational bandwidth of the PMUT by actuating the device with an appropriate voltage commensurate with the branch of nonlinearity one wishes to target. We report a bandwidth enhancement of up to 33 times using this technique.