An Aqueous Route to Oxygen-Deficient Wake-Up-Free La-Doped HfO₂ Ferroelectrics for Negative Capacitance Field Effect...

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Ferroelectric hafnia films are crucial for next-generation electronics.
• Stabilizing the orthorhombic phase typically requires nanocrystalline morphology and specific processing.
• Existing methods often involve carbon impurities or specialized electrodes.

Purpose of the Study:

• To develop a new method for stabilizing the ferroelectric orthorhombic phase in La-doped HfO2 films.
• To achieve wake-up-free ferroelectricity without relying on nanocrystalline structures or oxygen-scavenging electrodes.
• To investigate the role of oxygen vacancies in phase stabilization.

Main Methods:

• Chemical solution deposition (CSD) using engineered water-diluted precursors with low carbon content.
• Growth of large-grained (>100 nm) La-doped HfO2 films directly on silicon.
• Characterization of film properties, including phase, polarization, and electrical breakdown.

Main Results:

• Successfully stabilized the ferroelectric orthorhombic phase in large-grained La-doped HfO2 films.
• Achieved a maximum remnant polarization of 37.6 μC/cm² without a wake-up process.
• Films demonstrated high field endurance (>6.2 MV/cm) and improved MOSFET switching via negative capacitance.
• Uniformly distributed oxygen vacancies were identified as the key factor for o-phase stabilization.

Conclusions:

• Uniformly distributed oxygen vacancies are sufficient to stabilize the ferroelectric orthorhombic phase in La-doped HfO2 films.
• This approach enables wake-up-free ferroelectricity, eliminating the need for nanostructuring or reactive electrodes.
• The developed CSD method offers a promising route for fabricating high-performance ferroelectric devices.