Fabrication and characterization of PZT thin films for micromotors

Abstract

Piezoelectric membranes consisting of PbZr x Ti 1-x O 3 (PZT) films on silicon diaphragms have been fabricated, investigated, and applied for micromotors. The PZT films were deposited by sputtering and sol gel techniques. Resonance amplitudes of up to 1000 nm/V have been measured for 16 µm thick, 2 mm diameter membranes with 0.6 µm PZT. The PZT films show a preferred direction of polarization, which seems to depend on the deposition technique. Membranes of 4 mm diameter have been successfully applied as a vibrator of a micro motor, allowing for the first time the characterization of a PZT thin film micro motor. The motor could be operated with voltages as low as 1.0 Vrms, which is much less than has been obtained with ZnO micro motors and is sufficiently low for standard battery and IC supply voltages. A 100 h degradation test of frequency and amplitude has revealed a 5 % drop in amplitude, possibly due to depolarization.

Ferroelectric thin films for micro-sensors and actuators: a review

“…A dc field superimposed on the ac field helps in this case to maintain a good polarization. This is well seen in figure 6, where the motor speed is very much increased by a bias of only 2 V. Operation with unipolar fields (as, e.g., E(1 + sin ωt)) yield stable operating performance and also proved to be applicable during longer tests (100 h, see [65,86]). For some applications, such a dc bias might be an undesirable technical complication.…”

“…The same test was performed with a stator alone while measuring the vibration amplitude. A 5-10% decrease of the amplitude was observed [86]. Most likely this was due to depolarization.…”

“…The motor described above was subjected to a test lasting 100 h with a unipolar ac field of 20 kHz. Apart of a slight increase of the revolution speed, no deterioration was observed [86]. The same test was performed with a stator alone while measuring the vibration amplitude.…”

Flexural-standing-wave elastic force motor using ZnO and PZT thin film on micromachined silicon membranes for wristwatch applications

“…The mode symmetry of the larger resonance at the right of this spectrum was not of the form (2) U mn (r, θ ) = F (r) sin n(θ − θ 0 ) indicating that expected disk modes are no longer excited near the zero thickness limit. Deviation from disk behavior can be pointed out by the ratio of the frequencies B 10 /B 00 [23] as shown in figure 10. Ideal membrane behavior is approached with tensile PZT coated diaphragms on lowering the silicon thickness, as expected.…”

Piezoelectric properties of PZT films prepared by the sol–gel method and their application in MEMS

“…For MEMS application, Pb (Zr,Ti)O 3 (PZT) thin films are considered to be one of the most promising materials due to their excellent piezoelectric properties and, recently, have been applied in several types of microsensors and actuators [2,3]. In most of piezoelectric MEMS devices, PZT actuating and sensing parts are usually fabricated in flex-tensional structures such as cantilever, bridge, disk, and diaphragm or membrane [4][5][6].…”