DIELECTRIC AND ELECTROMECHANICAL PROPERTIES OF Pb(Zr,Ti)O3 THIN FILMS FOR PIEZO-MICROELECTROMECHANICAL SYSTEM DEVICES

The dielectric and electromechanical properties of 1-mu m-thick Pb(Zr,Ti)O3 (PZT) thin films with Zr/Ti ratio of 30/70, 52/48 and 70/30 are investigated. The magnitude of the effective longitudinal piezoelectric coefficient (d33) of these films is measured by a double-beam laser interferometric method. With increasing Ti-content, larger remanent polarization and higher coercive voltage are observed. The squareness of the polarization hysteresis loop is optimized in a Ti-rich composition. The remanent d33 values are maximized near a morphotropic phase boundary (MPB) composition, and the trend of d33 values depends on the dielectric constant. Maximum dielectric constant is achieved near MPB composition, showing the same trend as bulk PZT ceramics. This result indicates that the piezoelectric response in 1-mu m-thick films with composition (Zr to Ti ratio) is governed by extrinsic contribution such as that found in bulk PZT ceramics rather than intrinsic contribution. 13 refs.