Oxygen vacancies nucleate charged domain walls in ferroelectrics

TL;DR

This study demonstrates how oxygen vacancies in ferroelectric BaTiO$_3$ promote the formation of charged 180° domain walls, influencing their electronic properties and potential applications in information processing.

Contribution

It reveals that oxygen vacancies tend to cluster in planes, leading to charged domain walls with specific electronic characteristics, a novel insight into defect-domain wall interactions.

Findings

Vacancies assemble in crystallographic planes.

Charged domain walls are formed by vacancy clustering.

Different electronic conductivities are explained by vacancy effects.

Abstract

We study the influence of oxygen vacancies on the formation of charged 180$^\circ$ domain walls in ferroelectric BaTiO$_3$ using first principles calculations. We show that it is favorable for vacancies to assemble in crystallographic planes, and that such clustering is accompanied by the formation of a charged domain wall. The domain wall has negative bound charge, which compensates the nominal positive charge of the vacancies and leads to a vanishing density of free charge at the wall. This is in contrast to the positively charged domain walls, which are nearly completely compensated by free charge from the bulk. The results thus explain the experimentally observed difference in electronic conductivity of the two types of domain walls, as well as the generic prevalence of charged domain walls in ferroelectrics. Moreover, the explicit demonstration of vacancy driven domain wall formation implies that specific charged domain wall configurations may be realized by bottom-up design for use in domain wall based information processing.