Piezoelectric films for mems applications

Ferroelectric thin films are attractive for miniaturized piezoelectric and pyroelectric devices due to the substantial property coefficients that are available. This paper descibes the factors that control the magnitude of the piezoelectric response that can be achieved in thin films. The importance of composition, orientation, domain wall mobility, clamping by the substrate, and transition temperature will be discussed. These factors will be illustrated with data on lead zirconate titanate(PZT), lead magnesium niobate - lead titanate, lead ytterbium niobate-lead titanate, and bismuth scandale - lead titanate. It has been found that with (001) oriented thin films on the rhombohedral side of the morphotropic phase boundary, it is often possible to achieve e _31,f coefficients larger than -10C/m ², which is an order of magnitude larger than is available in ZnO or AlN films.