Defect and Strain Engineering Coenhanced Nanoscale Ferroelectricity in SrTiO₃ Thin Films

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• In-plane ferroelectricity in strontium titanate (SrTiO3) thin films is achievable via tensile biaxial strain at room temperature.
• Out-of-plane ferroelectricity is highly desirable for practical electronic device applications.

Purpose of the Study:

• To achieve room-temperature out-of-plane ferroelectric SrTiO3 thin films.
• To enhance ferroelectricity and thermal stability through material design.

Main Methods:

• Epitaxial strain and defect engineering were employed to modify SrTiO3 thin films.
• Optical second-harmonic generation (SHG) was used to verify ferroelectricity.
• Scanning transmission electron microscopy (STEM) and X-ray absorption near-edge spectroscopy (XANES) analyzed structural and electronic properties.

Main Results:

• Room-temperature out-of-plane ferroelectric SrTiO3 thin films with giant tetragonality (c/a ∼ 1.061) were successfully fabricated.
• An ultrahigh ferroelectric stability temperature (>1000 K) was achieved.
• Enhanced tetragonality directly correlates with improved ferroelectric properties, as confirmed by SHG.

Conclusions:

• Defect- and strain-codriven supertetragonal SrTiO3 thin films exhibit enhanced ferroelectricity.
• The findings demonstrate a viable approach for designing materials with enhanced ferroelectricity and emergent phenomena.
• This strategy is applicable to other material systems for advanced electronic applications.