Nucleation-to-Propagation Switching Modes in Ferroelectric Hf_0.5Zr_0.5O₂ Capacitors

Area of Science:

• Materials Science
• Solid-State Physics
• Nanotechnology

Background:

• Ferroelectric switching in hafnia-based materials is governed by nanoscale domain dynamics.
• The influence of electrode interfaces and thermal treatments on grain-scale switching mechanisms remains unclear.

Purpose of the Study:

• To investigate how bottom electrodes and annealing conditions affect polarization reversal in 10-nm-thick Hafnium Zirconium Oxide (Hf_0.5Zr_0.5O₂) capacitors.
• To establish a mechanistic link between material interfaces, microstructure, and switching kinetics at the grain scale.

Main Methods:

• Bias-dependent piezoresponse force microscopy (PFM) to probe ferroelectric domain behavior.
• Pulsed switching measurements to analyze polarization reversal kinetics.
• Quantitative analysis using a modified Kolmogorov-Avrami-Ishibashi (KAI) framework.

Main Results:

• Different bottom electrodes (TiN, NbN, MoO₂) exhibit distinct effects on polarization reversal: TiN promotes rapid nucleation and cross-grain propagation, NbN shows gradual intragrain switching, and MoO₂ suppresses switching.
• The fastest switching is achieved with TiN/Hf_0.5Zr_0.5O₂/TiN capacitors annealed at 600 °C, correlating with a fine-grained microstructure.
• Nucleation and growth processes were found to occur concurrently, with comparable time constants.

Conclusions:

• Electrode choice and annealing temperature are critical for controlling ferroelectric switching in Hf_0.5Zr_0.5O₂.
• A fine-grained microstructure with supportive grain boundaries enhances polarization reversal efficiency.
• The study provides a grain-scale understanding of how interfaces and processing influence switching kinetics in Hf_0.5Zr_0.5O₂ ferroelectrics.