Origin of ferroelectric domain wall alignment with surface trenches in ultrathin films

Abstract

Engraving trenches on the surfaces of ultrathin ferroelectric (FE) films and superlattices promises control over the orientation and direction of FE domain walls (DWs). Through exploiting the phenomenon of DW-surface trench (ST) parallel alignment, systems where DWs are known for becoming electrical conductors could now become useful nanocircuits using only standard lithographical techniques. Despite this clear application, the microscopic mechanism responsible for the alignment phenomenon has remained elusive. Using ultrathin PbTiO${}_3$ films as a model system, we explore this mechanism with large scale density functional theory simulations on as many as 5,136 atoms. Although we expect multiple contributing factors, we show that parallel DW-ST alignment can be well explained by this configuration giving rise to an arrangement of electric dipole moments which best restore polar continuity to the film. These moments preserve the polar texture of the pristine film, thus minimizing ST-induced depolarizing fields. Given the generality of this mechanism, we suggest that STs could be used to engineer other exotic polar textures in a variety of FE nanostructures as supported by the appearance of ST-induced polar cycloidal modulations in this letter. Our simulations also support experimental observations of ST-induced negative strains which have been suggested to play a role in the alignment mechanism.

arXiv comment13 pages, 6 figures

References in corpus (12)

• Optimized norm-conserving Vanderbilt pseudopotentials
• The PseudoDojo: Training and grading a 85 element optimized norm-conserving pseudopotential table
• O(N) methods in electronic structure calculations
• Comparative first-principles studies of prototypical ferroelectric materials by LDA, GGA, and SCAN meta-GGA
• Recent progress with large-scale ab initio calculations: the CONQUEST code
• Compositional Inversion Symmetry Breaking in Ferroelectric Perovskites
• Large scale and linear scaling DFT with the CONQUEST code
• Highly accurate local basis sets for large-scale DFT calculations in CONQUEST
• Domain Wall Orientations in Ferroelectric Superlattices Probed with Synchrotron X-Ray Diffraction
• Domain alignment within ferroelectric/dielectric PbTiO${}_3$/SrTiO${}_3$ superlattice nanostructures
• Polar morphologies from first principles: PbTiO${}_3$ films on SrTiO${}_3$ substrates and the $p(2\times \Lambda )$ surface reconstruction
• The pseudoatomic orbital basis: electronic accuracy and soft-mode distortions in ABO${}_3$ perovskites