Intrinsic Ferroelectric Polarization in Doped HfO₂ and ZrO₂

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Fluorite ferroelectrics, specifically hafnium oxide (HfO2) and zirconium oxide (ZrO2), are crucial for advanced memory devices.
• Controlling remanent polarization is key for optimizing device performance.
• Existing literature shows significant variability in reported polarization values for identical material compositions.

Purpose of the Study:

• To investigate and differentiate genuine ferroelectric properties from extrinsic contributions in HfO2 and ZrO2 films.
• To understand the impact of ionic transport and resistive switching on polarization measurements.
• To establish accurate methods for characterizing ferroelectricity in these materials.

Main Methods:

• Fabrication of high-quality epitaxial Hf1-xZrxO2 films with varying compositions (x=0 to 1).
• Systematic variation of deposition parameters and substrate orientations to control defects and interfaces.
• Analysis of electrical transport properties, including resistive switching and leakage currents.
• Measurement and critical evaluation of polarization-electric field (P-E) hysteresis loops.

Main Results:

• Resistive switching phenomena were observed, particularly in ZrO2-rich films.
• High leakage currents, influenced by ionic transport, lead to significant overestimation of polarization.
• Extrinsic contributions can mask or mimic genuine ferroelectric behavior, especially with abnormal P-E loops.

Conclusions:

• A critical assessment of extrinsic contributions, such as ionic transport and leakage currents, is essential for accurate ferroelectric characterization.
• Genuine ferroelectricity in HfO2 and ZrO2 can be obscured by measurement artifacts.
• This work provides a framework for reliable ferroelectric evaluation in fluorite-based memory materials.