Interfacial coherency and ferroelectricity of BaTiO_3/SrTiO_3 superlattice films

摘要

We studied the phase transitions, domain morphologies, and polarizations in BaTiO_3/SrTiO_3 superlattices grown on SrTiO_3 substrates. Using the phase field approach, we discovered the remarkable influence of film/substrate interfacial coherency on the ferroelectricity of the SrTiO_3 layers within a superlattice: it is an orthorhombic ferroelectric for an incoherent interface while it exhibits only induced polarization by the adjacent BaTiO_3 layers for a coherent interface. We presented the domain morphologies within individual BaTiO_3 and SrTiO_3 layers which have different ferroelectric symmetries. The results are compared to ultraviolet Raman spectroscopy and variable temperature x-ray diffraction measurements.