  Strain engineering of perovskite oxide thin films has proven to be an
extremely powerful method for enhancing and inducing ferroelectric behavior. In
ferroelectric thin films and superlattices, the polarization is intricately
linked to crystal structure, but we show here that it can also play an
important role in the growth process, influencing growth rates, relaxation
mechanisms, electrical properties and domain structures. We have studied this
effect in detail by focusing on the properties of BaTiO$_{3}$ thin films grown
on very thin layers of PbTiO$_{3}$ using a combination of x-ray diffraction,
piezoforce microscopy, electrical characterization and rapid in-situ x-ray
diffraction reciprocal space maps during the growth using synchrotron
radiation. Using a simple model we show that the changes in growth are driven
by the energy cost for the top material to sustain the polarization imposed
upon it by the underlying layer, and these effects may be expected to occur in
other multilayer systems where polarization is present during growth. Our
research motivates the concept of polarization engineering during the growth
process as a new and complementary approach to strain engineering.
