PZT thin film bi-layer devices for phase controlled actuation in MEMS

A potential application for ferroelectric thin films is micro positioning a nd actuation. For using PZT films as micro-actuators it is desirable to hav e film thicknesses of comparable size to the underlying structure. The amou nt of actuation possible is determined by a number of factors: the piezoele ctric coefficient d(3)1, geometric factors and the compliance of both the a ctuator and cantilever and the electric field across the film. Using a bi-l ayer should therefore increase the amount of actuation for a given drive vo ltage. Bi-layer devices can also be driven at constant voltage, and their a ctuation varied by the phase difference of the drive voltage between the tw o layers. PZT films of thickness 0.5 mum have been deposited as a bi-layer. Micro-actuators have been fabricated using these structures, their electri c properties measured and their electro-mechanical properties characterised and evaluated using optical beam deflection.