Search

It has been recognized that the control of crystalline orientation and thickness of Pb(Zr0.52Ti0.48)O3 (PZT) thin-films is very critical in the fabrication of piezoelectric thin-film devices with desirable dielectric and electromechanical properties. Here, we present our recent studies on the fabrication of PZT films with (001), (111), and random crystalline orientations onto platinized silicon substrates and the crystalline orientation dependence of the nanomechanical properties. A 1.0-μm PZT film with a strong (100) orientation is deposited by a 2–methoxyethanol- (2–MOE)-based sol–gel precursor solution, while random orientation is obtained by acetic acid-based sol–gel precursor. Rapid thermal annealing of 2–MOE sol-gel-based PZT films leads to strong (111) orientation. All PZT films show similar hysteresis behavior and large remnant polarizations; however, the nanomechanical test using AFM and nanoindentation indicates distinct values of Young’s modulus for PZT films with different orientations.

The input electric impedance Zin for a three-layer thin-film bulk acoustic wave resonator is derived by transfer matrix method to describe the resonator behavior. Based on the impedance spectra, the effective coupling coefficient keff2 of a thin-film resonator can be evaluated with respect to the resonator structure and thin-film properties. The results for both AlN and lead zirconate titanate thin-film resonators reveal that the mechanical Q factor of the thin-film piezoelectric material has a significant effect on the effective coupling coefficient keff2 of the device. keff2 decreases with theincrease of the mechanical quality factor Q. A maximum keff2 value can be obtained at an appropriate thickness ratio of electrode/piezoelectric layers.