Piezoelectric films for MEMS applications

Piezoelectric thin films are attractive for applications in MicroElectroMechanical Systems (MEMS) due to the combination of high energy density and low power requirements relative to other on-chip actuation mechanisms. As such, they can be utilized for applications as diverse as the pumping systems in miniature analytical instrumentation, high sensitivity accelerometers and hydrophones, miniature motors, and high frequency biomedical ultrasound, for example. Critical in all of these applications is the magnitude of the electromechanical response that can be generated. This paper will focus on the factors which affect the measured piezoelectric response of ferroelectric thin films. Particular emphasis will be placed on the effects of substrate clamping, clamping of the extrinsic contributions to the properties, and the role of preferred polarization directions in increasing the long-term reliability of ferroelectric films for piezoelectric applications.