Ferroelectric Negative Capacitance Domain Dynamics

TL;DR

This paper investigates the transient negative capacitance in ferroelectric Pb(Zr,Ti)O3 capacitors, revealing how domain nucleation and growth govern switching behavior and how this can be controlled and modeled.

Contribution

It introduces a new method for extracting the average negative capacitance and develops an analytical model describing the transient behavior based on domain dynamics.

Findings

Negative capacitance originates from reverse domain nucleation and growth.

Capacitance becomes positive again during domain coalescence.

Domain wall velocity can be controlled by electric field, area, or resistance.

Abstract

Transient negative capacitance effects in epitaxial ferroelectric Pb(Zr$_{0.2}$Ti$_{0.8}$)O$_3$ capacitors are investigated with a focus on the dynamical switching behavior governed by domain nucleation and growth. Voltage pulses are applied to a series connection of the ferroelectric capacitor and a resistor to directly measure the ferroelectric negative capacitance during switching. A time-dependent Ginzburg-Landau approach is used to investigate the underlying domain dynamics. The transient negative capacitance is shown to originate from reverse domain nucleation and unrestricted domain growth. However, with the onset of domain coalescence, the capacitance becomes positive again. The persistence of the negative capacitance state is therefore limited by the speed of domain wall motion. By changing the applied electric field, capacitor area or external resistance, this domain wall velocity can be varied predictably over several orders of magnitude. Additionally, detailed insights into the intrinsic material properties of the ferroelectric are obtainable through these measurements. A new method for reliable extraction of the average negative capacitance of the ferroelectric is presented. Furthermore, a simple analytical model is developed, which accurately describes the negative capacitance transient time as a function of the material properties and the experimental boundary conditions.