First-principles modeling of ferroelectric capacitors via constrained-D calculations

TL;DR

This paper introduces a finite-field density-functional theory approach using the displacement field D to model ferroelectric capacitors, enabling detailed analysis of interface and bulk properties and their influence on electrical behavior.

Contribution

It presents a novel methodology for first-principles modeling of ferroelectric capacitors that separates interface and bulk effects using the displacement field D.

Findings

Interface-specific properties can be rigorously separated from bulk properties.

Electrical properties of capacitors of various geometries can be reconstructed from model data.

BO2-electrode interfaces act like a linear dielectric in series with the bulk, while AO-electrode interfaces show nonlinear effects.

Abstract

First-principles modeling of ferroelectric capacitors presents several technical challenges, due to the coexistence of metallic electrodes, long-range electrostatic forces and short-range interface chemistry. Here we show how these aspects can be efficiently and accurately rationalized by using a finite-field density-functional theory formalism in which the fundamental electrical variable is the displacement field D. By performing calculations on model Pt/BaTiO3/Pt and Au/BaZrO3/Au capacitors we demonstrate how the interface-specific and bulk-specific properties can be identified and rigorously separated. Then, we show how the electrical properties of capacitors of arbitrary thickness and geometry (symmetric or asymmetric) can be readily reconstructed by using such information. Finally, we show how useful observables such as polarization and dielectric, piezoelectric and electrostrictive coefficients are easily evaluated as a byproduct of the above procedure. We apply this methodology to elucidate the relationship between chemical bonding, Schottky barriers and ferroelectric polarization at simple-metal/oxide interfaces. We find that BO2-electrode interfaces behave analogously to a layer of linear dielectric put in series with a bulk-like perovskite film, while a significant non-linear effect occurs at AO-electrode interfaces.