Direct measurement of piezoelectric properties of Sol-Gel PZT films

PbZr0.53Ti0.47O3 films were deposited on Si-SiO2-Ta-Pt substrates via a conventional sol-gel procedure. Electrical properties of the films were: resistivity ca. 5 × 1011 Ωcm, relative dielectric permittivity 900-1100, remnant polarization ca. 20 μC/cm2, breakdown electric field larger than 50 MV/m. The deflection amplitude of piezoelectrically excited Si cantilevers, covered with SiO2-Ta-Pt-PZT-Al, was determined with the aid of a heterodyne Mach-Zehnder interferometer. The piezoelectric strain constant d31 of the PZT films was determined from the amplitude measured at frequencies far below the first mechanical resonance (quasi-static method). The d31 constant was also determined from the deflection amplitude at the first mechanical resonance and the quality factor of the cantilever. Measured values ranged from -30 pC/N for unpoled films to -160 pC/N for films poled at room temperature and 40 MV/m.