Increased ferroelastic domain mobility in ferroelectric thin films and its use in nano-patterned capacitors

Movements of ferroelastic 90 degrees a-domains ( twins) of sub-100 nm lateral size contribute greatly to the dielectric, piezoelectric, and elastic properties of ferroelectric materials. However, in thin films the mobility of twins is severely limited due to substrate clamping and pinning of domain walls. Here we demonstrate the possibility of moving ferroelastic domains by applying a non-uniform electric field. By means of piezoresponse force microscopy (PFM), it is shown that 90 degrees domains in epitaxial Pb(Zr0.2Ti0.8) O-3 (PZT) continuous films are highly mobile. Following this observation, capacitors with stripe-shaped top electrodes have been designed, which show a reversible increase in the piezoelectric signal, as well as an increase of the specific capacitance by a factor of 1.4. The present concept of non plane-parallel electrodes might be useful for redesigning devices such as multilayered capacitors or sensors and actuators based on ferroelectric thin films.