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Interfacial Charge-Injection-Induced Ferroelectric Phase Instability in Epitaxial Yttrium-Doped Hafnium Oxide Films
Jie Tu1, Chengfeng Pan1, Xiaoyu Qiu1
1Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, 200241 Shanghai, China.
ACS Applied Materials & Interfaces
|December 4, 2025
Summary
Interfacial charge transfer, not chemistry, dictates ferroelectric phase in Y-doped HfO2 (YHO) films. Excessive holes from LaNiO3 (LNO) electrodes suppress ferroelectricity by destabilizing the YHO phase.
Area of Science:
- Materials Science
- Solid State Physics
- Nanotechnology
Background:
- Ferroelectric properties of hafnia-based capacitors are influenced by electrode interfaces.
- The precise physical mechanisms behind these interface effects remain unclear.
- Epitaxial hafnia films offer a controlled system to investigate ferroelectric-electrode interactions.
Purpose of the Study:
- To elucidate the role of interfacial charge transfer versus interface chemistry in determining the phase structure of Y-doped HfO2 (YHO) films.
- To investigate how different electrode materials (LaNiO3 and La2/3Sr1/3MnO3) affect YHO phase composition and ferroelectricity.
- To understand the impact of electrode architecture (capping layer vs. bottom electrode) on YHO film properties.
Main Methods:
- Fabrication of epitaxial Y-doped HfO2 (YHO) capacitors with varied architectures.
- X-ray absorption spectroscopy (XAS) to probe interfacial charge transfer.
- Density functional theory (DFT) calculations to determine work functions of electrode materials.
- Electrical characterization of ferroelectric properties (polarization).
Main Results:
- Interfacial charge transfer significantly influences YHO phase structure, overriding interface chemistry.
- XAS revealed greater charge transfer at the LaNiO3 (LNO)/YHO interface than at the La2/3Sr1/3MnO3 (LSMO)/YHO interface.
- Excessive hole injection from LNO destabilizes the ferroelectric phase and suppresses polarization in YHO films.
- LNO as a capping layer primarily affects the near-surface region, while as a bottom electrode, it induces a nonpolar-phase-dominated film.
Conclusions:
- Interfacial charge transfer is the dominant factor controlling ferroelectricity in YHO films.
- Electrode work function differences correlate with the extent of interfacial charge transfer.
- Understanding and controlling interfacial charge transfer is crucial for engineering ferroelectricity in hafnia-based materials.
