Domain engineering in ferroelectric thin films by nanopatterned bottom electrodes

Ferroelectric thin films are used in a wide range of device applications from MEMS sensors and actuators to non-volatile random access memories. The wide range of applications is due to several attractive properties of ferroelectrics such as high dielectric permittivities and reversible spontaneous polarization. The domain structure of a ferroelectric film has a large influence on the properties of the film and therefore controlling the domain structure is essential to optimize their properties and performance. Furthermore, different applications of ferroelectric thin films need different domain structures for optimum performance. Domain engineering has been achieved by control of the misfit strain through epitaxial growth on substrates with different lattice constants. However, this method only influences the relative domain populations and does not allow specific control over the domain structure.
Here we report domain engineering in ferroelectric thin films by using a nanopatterened bottom electrode. Pulsed laser deposition epitaxial grown ferroelectric thin films of PbTiO3 and BiFeO3 have been grown on self assembled SrRuO3 nanopatterns 5nm thick and with lateral dimensions of 100-200nm. The patterned SrRuO3 changes the mechanical boundary conditions of the ferroelectric film and as a result new domain structures are obtained with features corresponding to the SrRuO3 patterns. This technique allows nanometer control of the domain structure in ferroelectric films that has not previously been achieved.