Polar Morphologies from First Principles: PbTiO3 Films on SrTiO3 Substrates and the p(2×Λ) Surface Reconstruction

Jack S Baker,David R Bowler

doi:10.1002/adts.202000154

Abstract

AbstractLow‐dimensional structures comprised of ferroelectric (FE) PbTiO3 (PTO) and quantum paraelectric SrTiO3 (STO) are hosts to complex polarization textures such as polar waves, flux‐closure domains, and polar skyrmion phases. Density functional theory (DFT) simulations can provide insight into this order, but are limited by the computational effort required. Within DFT, the novel multi‐site support function method is used to reduce the solution time for the electronic groundstate whilst preserving high accuracy. This allows for large‐scale simulations of PTO films on STO substrates with system sizes >2000 atoms. In the ultrathin limit, the polar wave texture with cylindrical chiral bubbles emerges as an intermediate phase between full‐flux‐closure domains and in‐plane polarization. This is driven by an internal bias field born of the compositionally broken inversion symmetry in the [001] direction. Manipulation of this built‐in field informs a new principle of design for control over chiral order on the nanoscale through the careful choice of substrate, surface termination, or use of overlayers. Antiferrodistortive (AFD) order locally interacts with these polar textures giving rise to strong FE/AFD coupling at the PbO terminated surface driving a surface reconstruction. This offers another pathway for the local control of ferroelectricity.

Highlights

Further complex phenomena can arise by the interacting order parameters of the system
This method has allowed for the explicit simulation of the STO substrate, multiple ferroelectric domains, and doubled periodicity in the [010] direction used include AFD modes and the surface reconstruction
We have demonstrated the stability of the polydomain film geometry compared to monodomain phases

Summary

Introduction

Further complex phenomena can arise by the interacting order parameters of the system. With the advent of advanced deposition techniques[1,2] has come heterostructures) are susceptible to both the antiferrodistortive a revolution in the engineering of thin film perovskite oxides and (AFD) and FE distortions. In the bulk, these two modes were layered heterostructures for a variety of applications in nanoelec- thought to suppress one another, recent evidence sugtronics. These two modes were layered heterostructures for a variety of applications in nanoelec- thought to suppress one another, recent evidence sugtronics These advancements have propelled research into the gests that a cooperative regime may exist.[21,22] At surfaces great variety of physical phenomena such systems can exhibit. At the PbO terminated [001] surface of PTO, we observe the AFD c(2 × 2)

Methods

Results

Conclusion