Interaction Between Strain and Phase Formation in Hf_xZr_1-xO₂ Thin Films.

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Hafnium-zirconium oxide (Hf_xZr_1-xO₂) thin films are promising for non-volatile memory due to their CMOS compatibility.
• Polymorphism in Hf_xZr_1-xO₂ hinders stable ferroelectric properties, crucial for wake-up free applications.

Purpose of the Study:

• To investigate the influence of in-plane tensile strain on the phase formation of Hf_xZr_1-xO₂ thin films.
• To understand strain-phase formation interactions for optimizing ferroelectric properties in the pristine state.

Main Methods:

• Atomic layer deposition (ALD) of Hf_xZr_1-xO₂ thin films with varying thicknesses and compositions.
• Application of biaxial in-plane tensile strain.
• Electrical characterization including switching field and remanent polarization measurements.

Main Results:

• A correlation between in-plane tensile strain and phase formation in Hf_xZr_1-xO₂ films was demonstrated.
• Optimal ferroelectric properties were observed within an in-plane tensile strain range of 0.4-0.6%.
• Strain influences initial phase formation, which in turn affects strain during electrical cycling.

Conclusions:

• In-plane tensile strain is a critical factor in promoting the ferroelectric orthorhombic phase in Hf_xZr_1-xO₂ films.
• Understanding strain-phase interactions is key to achieving wake-up free ferroelectric memory devices.
• This research provides insights for tailoring Hf_xZr_1-xO₂ films for specialized memory applications.