PZT Thin Film Bi-Layer Devices for Phase Controlled Actuation in MEMS

A potential application for ferroelectric thin films is micro positioning and actuation. For using PZT films as micro-actuators it is desirable to have film thicknesses of comparable size to the underlying structure. The amount of actuation possible is determined by a number of factors: the piezoelectric coefficient d ₃₁, geometric factors and the compliance of both the actuator and cantilever and the electric field across the film. Using a bi-layer should therefore increase the amount of actuation for a given drive voltage. Bi-layer devices can also be driven at constant voltage, and their actuation varied by the phase difference of the drive voltage between the two layers. PZT films of thickness 0.5 m have been deposited as a bi-layer. Micro-actuators have been fabricated using these structures, their electric properties measured and their electro-mechanical properties characterised and evaluated using optical beam deflection.