Abstract
This work focuses on the validation of a possible connection of the known Ruddlesden-Popper (RP) phases and the novel concept of the migration-induced field-stabilized polar (MFP) phase. To study this subject, model structures of RP phases in bulk strontium titanate are analyzed by means of density functional theory (DFT). The obtained geometries are compared to experimental MFP data. Good agreement can be found concerning atomic displacements in the pm range and lattice strain inferred by the RP phases. Looking at the energy point of view, the defect structures are on the convex hull of the Gibb’s free energy. Although the dynamics to form the discussed defect models are not addressed in detail, the interplay and stability of the described defect model will add to the possible structure scenarios within the near-surface region of strontium titanate. As a result, it can be suggested that RP phases generally favor the MFP formation.
Highlights
Strontium titanate as a representative of transition metal oxides has been in the focus of research for many years
Comparing the structures RP1 and RP1+, it shows that the increased number of strontium titanate layers compensates the stress better, which the RP phase embedded in the supercell induces onto the SrTiO3 cubic unit cells, resulting in a smaller ∆c value
In this work the concept of the migration-induced field-stabilized polar (MFP) phase distribution in strontium titanate is analyzed with a new approach: The presence of RP phases in bulk strontium titanate could influence the conditions in such a system in the way that the formation of the MFP phase may be favored
Summary
Strontium titanate as a representative of transition metal oxides has been in the focus of research for many years. Richter et al [26] analyzed the MFP phase with Resonantly Suppressed Diffraction (RSD), a new approach of Resonant X-ray Diffraction. With this method they were able to determine atomic displacements in strontium titanate on the picometer scale during phase transformation. They found a dependency between strain and the displacements
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