Interfacial coherency and ferroelectricity of $BaTiO3∕SrTiO3$ superlattice films

We studied the phase transitions, domain morphologies, and polarizations in $BaTiO3∕SrTiO3$ superlattices grown on $SrTiO3$ substrates. Using the phase field approach, we discovered the remarkable influence of film/substrate interfacial coherency on the ferroelectricity of the $SrTiO3$ layers within a superlattice: it is an orthorhombic ferroelectric for an incoherent interface while it exhibits only induced polarization by the adjacent $BaTiO3$ layers for a coherent interface. We presented the domain morphologies within individual $BaTiO3$ and $SrTiO3$ layers which have different ferroelectric symmetries. The results are compared to ultraviolet Raman spectroscopy and variable temperature x-ray diffraction measurements.