Defect engineering for enhanced stability and spontaneous polarization in rhombohedral HfO2: First-principles...

Area of Science:

• Materials Science
• Solid State Physics
• Computational Materials Science

Background:

• Rhombohedral R3-HfO2 exhibits significant ferroelectric polarization (41 μC/cm2), making it promising for memory and logic devices.
• The stability and ferroelectric properties of R3-HfO2 are highly susceptible to intrinsic point defects.

Purpose of the Study:

• To investigate the impact of intrinsic point defects on the stability and ferroelectric polarization of R3-HfO2.
• To explore defect engineering strategies for enhancing R3-HfO2 properties through first-principles calculations.

Main Methods:

• First-principles calculations were employed to simulate defect formation and analyze their effects.
• The study examined defect behavior under varying Hf and O stoichiometry (Hf-poor, O-poor, Hf-rich, O-rich conditions).

Main Results:

• High concentrations of point defects form under Hf-poor or O-poor conditions; moderate Hf-rich and O-rich conditions are optimal for defect suppression.
• On-diagonal defects preserve R3 symmetry and ferroelectricity, while off-diagonal defects induce paraelectricity.
• Oxygen vacancies (VO) act as dominant donors, while interstitial oxygen (Oi) and hafnium vacancies (VHf) act as dominant acceptors.

Conclusions:

• Defect engineering is critical for fabricating high-quality, stable R3-HfO2 thin films with enhanced ferroelectric polarization.
• Interstitial oxygen (Oi) increases polarization by 24.4%, whereas hafnium vacancies (VHf) decrease it by 66.5%, highlighting selective defect control benefits.