Ferroelectric Tunnel Junction for Dense Cross-Point Arrays

Area of Science:

• Materials Science
• Electrical Engineering
• Solid State Physics

Background:

• Cross-point array (CPA) structures offer high-density memory integration (4F2 cell).
• Crosstalk between cells is a significant drawback in CPA configurations.
• Redox-based memristors in CPA structures face limitations in minimizing operating current due to their switching mechanism.

Purpose of the Study:

• To demonstrate the suitability of ferroelectric tunnel junctions (FTJs) as memristors in CPA structures.
• To address the crosstalk issue and low operating current limitations in CPA memories.
• To investigate the electrostatic properties of FTJs for memristive applications.

Main Methods:

• Utilized an electrostatic model to analyze FTJ characteristics.
• Fabricated and characterized an FTJ device with a specific layered structure (Au/p-type Pr0.98Ca0.02MnO3/BaTiO3/n-type Ca0.98Pr0.02MnO3/Pt(111)).
• Analyzed current-voltage (I-V) curves to evaluate memristive behavior.

Main Results:

• The FTJ exhibited a memristive effect suitable for CPA structures, characterized by a high nonlinear current-voltage curve.
• Achieved low current operation due to a higher and thicker potential barrier in the FTJ.
• Demonstrated effectively blocked direct tunneling and thermionic emission, enabling Fowler-Nordheim tunneling.
• Observed reduced sneak current and high nonlinearity, mitigating CPA crosstalk issues.

Conclusions:

• Ferroelectric tunnel junctions (FTJs) show promise as memristors for high-density CPA memory applications.
• The demonstrated FTJ structure effectively suppresses sneak currents and enables low-power operation.
• FTJs provide a viable pathway to overcome the crosstalk limitations inherent in traditional CPA architectures.