Competing Charge Transfer and Screening Effects in Two-Dimensional Ferroelectric Capacitors

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) ferroelectrics are crucial for next-generation ultrathin flexible nanoelectronics.
• Metal-ferroelectric-metal structures are commonly employed in 2D ferroelectric capacitors.
• Electrodes critically influence ferroelectric properties by screening depolarization fields or inducing charge doping.

Purpose of the Study:

• To investigate the dual roles of electrodes in 2D ferroelectric capacitors.
• To understand the impact of electrode work functions on ferroelectric behavior.
• To elucidate the interplay between charge transfer and screening effects.

Main Methods:

• First-principles calculations were performed.
• A range of electrode work functions were explored.
• Ferroelectric-electrode binding affinity and transferred interfacial charge were analyzed.

Main Results:

• Volcano-type relationships were observed between binding affinity and work function.
• A quadratic scaling was found between binding energy and transferred charge.
• Charge transfer dictates ferroelectric stability and switching at the monolayer limit.
• Capacitor stability transitions from charge-transfer to screening dominance with increasing thickness.

Conclusions:

• The findings are general and confirmed across various 2D ferroelectrics (α-In2Se3, CuInP2S6, SnTe).
• The interplay between charge transfer and screening is critical for designing 2D ferroelectric capacitors.
• Understanding these electrode effects is vital for advancing nanoscale ferroelectric device applications.