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 REScO3 (RE: rare earth elements) substrates have shown great capabilities for mediating these novel ferroelectric topologies. However, there are large difficulties for preparing high quality REScO3 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 REScO3 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 PrScO3 buffer layer was deposited on a conventional SrTiO3(001) substrate and then annealed at 800 ℃. Transmission electron microscopy (TEM) investigations revealed the high quality of the obtained PrScO3 films with almost no threading dislocations, where the mismatch with the SrTiO3 substrate was relaxed by misfit dislocations and thus a relaxed PrScO3 buffer layer was obtained. Atomic scale studies based on the advanced TEM methods revealed that periodic flux-closure arrays in PbTiO3 layers were successfully obtained, in the later PbTiO3/SrTiO3 multilayer films grown on the PrScO3 buffered SrTiO3 substrates. These results suggest that the PrScO3 buffer layer here can serves as the common REScO3 single-crystal substrates. This study provides a practical way to prepare REScO3 buffer layers serving as strain engineering ingredient for creating exotic phenomena in perovskite oxide heterostructures.