Achieving Ferroelectricity in a Centrosymmetric High-Performance Semiconductor by Strain Engineering.

Area of Science:

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

Background:

• Strain engineering is crucial for tuning properties of 2D semiconductors.
• Bismuth oxyselenide (Bi2O2Se) is a high-performance semiconductor with potential for next-generation electronics.
• Ferroelectric (FE) materials exhibit spontaneous electric polarization, but achieving this in Bi2O2Se is challenging.

Purpose of the Study:

• To investigate the strain-induced ferroelectric (FE) transition in bismuth oxyselenide (Bi2O2Se) films.
• To explore the potential applications of this FE transition in electronic devices.
• To understand the fundamental mechanisms behind the strain-induced FE behavior.

Main Methods:

• Applying controlled mechanical strain to Bi2O2Se films.
• Measuring piezoelectric force microscopy (PFM) to observe ferroelectric domain switching.
• Utilizing optical second-harmonic generation (SHG) to detect phase transitions.
• Performing first-principles calculations and theoretical simulations to model the FE transition.

Main Results:

• Bi2O2Se films transition to a ferroelectric phase under applied strain (loading force ≳400 nN).
• Observed butterfly loops in piezoelectric force responses and 180° phase switching indicate FE behavior.
• A sharp peak in optical second-harmonic generation confirms the strain-induced phase transition.
• Exclusion of extrinsic factors validates the intrinsic nature of the FE transition.

Conclusions:

• Strain can induce a rare ferroelectric phase in materials that are paraelectric at ambient pressure.
• Switching ferroelectric polarization allows for Schottky barrier engineering and memristor applications with high on/off ratios (10^6).
• The integration of ferroelectricity and high-performance semiconductivity in Bi2O2Se opens avenues for advanced neuromorphic computing and piezophotovoltaics.