Orientation-Confinement-Engineered Stabilization of Ferroelectricity in HfO₂ toward Maximum Polarization

Area of Science:

• Materials Science
• Solid State Physics
• Computational Materials Science

Background:

• Ferroelectric hafnium oxide (HfO2)-based materials are key for memory applications due to CMOS compatibility.
• The ferroelectric phase of HfO2 is metastable, leading to poorly understood stabilization mechanisms and polarization variations.

Purpose of the Study:

• To investigate methods for stabilizing the ferroelectric phase in HfO2-based materials.
• To understand and account for variations in measured polarization magnitudes.
• To identify strategies for designing high-performance ferroelectric memory devices.

Main Methods:

• Density Functional Theory (DFT) simulations were used to model material properties.
• Experimental measurements were combined with theoretical calculations.
• Calculations explored electric polarization along various crystal orientations, including crossing and non-crossing switching paths.

Main Results:

• Confinement to (111) crystallographic orientation effectively stabilizes the ferroelectric phase in Hf0.5Zr0.5O2 films.
• Crossing switching paths consistently yield high polarization values.
• High switching barriers in crossing paths limit their experimental observation, while specific dopants and oxygen vacancies were identified to lower these barriers and maximize polarization (~70 µC/cm2).

Conclusions:

• The (111) orientation is preferred for stabilizing ferroelectricity in HfO2-based films.
• Understanding polarization switching paths is crucial for device performance.
• Tailoring film composition with specific dopants and oxygen vacancies can optimize ferroelectric properties for advanced memory applications.