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 w ere: resistivity ca. 5 x 10(11) Omega cm, relative dielectric permitti vity 900-1100, remnant polarization ca. 20 mu C/cm(2), breakdown elect ric field larger than 50 MV/m. The deflection amplitude of piezoelectr ically excited Si cantilevers, covered with SiO2-Ta-Pt-PZT-Al, was det ermined with the aid of a heterodyne Mach-Zehnder interferometer. The piezoelectric strain constant d(31) of the PZT films was determined fr om the amplitude measured at frequencies far below the first mechanica l resonance (quasi-static method). The d(31) constant was also determi ned from the deflection amplitude at the first mechanical resonance an d the quality factor of the cantilever. Measured values ranged from -3 0 pC/N for unpoled films to -160 pC/N for films poled at room temperat ure and 40 MV/m.