Electromechanical properties of Pb(Zr,Ti)O3 films for MEMS applications

A systematic investigation of the piezoelectric and ferroelectric properties of PZT films prepared by chemical solution deposition is performed for tetragonal (Zr/Ti = 30/70), morphotropic (52/48), and rhombohedral (70/30) composition. An atomic force microscope (AFM) is used to measure the magnitude of the effective longitudinal piezoelectric coefficient (d(33)) of these films. All films are consistently highly textured (111) orientation and have dense microstructures. Slightly less degree of texture in higher Zr-rich composition is observed due to the lattice mismatch between PZT and Pt bottom electrode and higher activation energy for nucleation. Squareness of polarization hysteresis loops is optimized in tetragonal composition, which indicates the tetragonal PZT is closer to the ideal hysteresis behavior than other composition. It is shown that the piezoelectric coefficient is dependent on the dielectric constant. The morphotropic PZT films with 1 mum thickness show the largest piezoelectric coefficient values, which are comparable with those of bulk materials.