Theoretical investigation of polarization-compensated II-IV/I-V perovskite superlattices

TL;DR

This paper provides a theoretical analysis of polarization compensation in II-IV/I-V perovskite superlattices, demonstrating stable polarization regions and large discontinuities at interfaces through first-principles calculations.

Contribution

It introduces a novel superlattice design using polar discontinuities at interfaces and extends a Wannier-based polarization definition to non-neutral layers.

Findings

Superlattices with stable polarized regions are achievable.

Large polarization discontinuities occur at internal interfaces.

The extended polarization definition accurately quantifies local polarization variations.

Abstract

Recent work suggested that head-to-head and tail-to-tail domain walls could be induced to form in ferroelectric superlattices by introducing compensating "delta doping" layers via chemical substitution in specified atomic planes [Phys. Rev. B 73, 020103(R), 2006]. Here we investigate a variation of this approach in which superlattices are formed of alternately stacked groups of II-IV and I-V perovskite layers, and the "polar discontinuity" at the II-IV/I-V interface effectively provides the delta-doping layer. Using first-principles calculations on SrTiO3/KNbO3 as a model system, we show that this strategy allows for the growth of a superlattice with stable polarized regions and large polarization discontinuities at the internal interfaces. We also generalize a Wannier-based definition of layer polarizations in perovskite superlattices [Phys. Rev. Lett. 97, 107602 (2006)] to the case in which some (e.g., KO or NbO2) layers are non-neutral, and apply this method to quantify the local variations in polarization in the proposed SrTiO3/KNbO3 superlattice system.