Properties of piezoelectric thin films for micromechanical devices and systems

Zinc oxide and ferroelectrics of the lead zirconate titanate (PZT) family are candidates for piezoelectric actuation as well as sensing elements in microelectromechanical systems. In this work the relevant properties of the thin film forms of these materials are characterized, including the induced stress, the Young´s modulus, and the electromechanical coupling (piezoelectric) constants. Pyroelectric and dielectric properties (permittivity and resistivity) were also investigated. The mechanical properties in thin film ZnO and PZT were found to be favorable for their use in micromachining. The piezoelectric coefficients found for these films are also favorable for microactuation. Electrical properties in both ZnO and PZT were found to be sensitive to substrate material stress surface and surface condition. The relatively high pyroelectric coefficients measured in these films suggest the possible need for ambient temperature-cancellation schemes in micromechanical structures. Demonstration of micromachining using these films suggests that the film deposition technology as it exists now is suitable for achieving piezoelectrically induced motion on the microscale