Strain engineering of ferroelectric topologies prepared on conventional SrTiO3 substrates buffered with REScO3 layers

Strain engineering of low dimensional ferroelectrics has achieved substantial progresses such as the finding of ferroelectric topologies as flux-closures, vortices, skyrmions, merons and polar waves identified in strain mediated ferroelectric multilayers/superlattices or single-layer films. Particularly, tensile strains from REScO ₃ (RE: rare earth elements) substrates have shown great capabilities for mediating these novel ferroelectric topologies. However, there are large difficulties for preparing high quality REScO ₃ single-crystal substrates. This fact has induced large obstacles for exploring the structures and properties of ferroelectric topologies. Here we propose a practical way to prepare REScO ₃ ultrathin films by a combination of precision pulsed laser deposition (PLD) and controlled post-annealing, which shows the same strain engineering effects on preparing ferroelectric polar topologies. A PrScO ₃ buffer layer was deposited on a conventional SrTiO ₃ (001) substrate and then annealed at 800 ℃. Transmission electron microscopy (TEM) investigations revealed the high quality of the obtained PrScO ₃ films with almost no threading dislocations, where the mismatch with the SrTiO ₃ substrate was relaxed by misfit dislocations and thus a relaxed PrScO ₃ buffer layer was obtained. Atomic scale studies based on the advanced TEM methods revealed that periodic flux-closure arrays in PbTiO ₃ layers were successfully obtained, in the later PbTiO ₃/SrTiO ₃ multilayer films grown on the PrScO ₃ buffered SrTiO ₃ substrates. These results suggest that the PrScO ₃ buffer layer here can serves as the common REScO ₃ single-crystal substrates. This study provides a practical way to prepare REScO ₃ buffer layers serving as strain engineering ingredient for creating exotic phenomena in perovskite oxide heterostructures.