Creep behavior of undoped and La–Nb codoped PZT based micro-piezoactuators for micro-optical modulator applications

Time-dependent deformation (creep) behaviors of piezoelectric microactuators have been investigated. Position (or gap height) drift of microbridged actuator beam and its displacement amplitude change with time could be attributed to the anelastic behavior of the driving unit itself based on lead zirconate titanate (PZT) in the actuator, and as well as to the mechanical stress states established in the microactuator beam after the surface release of the micromachined actuator structure. From creep analyses of a simple microcantilever and microbridge beam structures, it was turned out that the overall creep behavior in microbridged piezoactuator structure was mainly dependent on the actuator beam initial deflection configuration governed both by residual stress of the actuating part Pt/PZT/Pt stack and the stress gradient through the silicon nitride (SiNx) microbridge beam.