Unveiling Negative Differential Resistance and Superionic Conductivity: Water Anchored on Layered Materials

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Negative differential resistance (NDR) in 2D transition metal dichalcogenide (2D TMD) devices is poorly understood due to ambient conditions.
• Investigating intrinsic NDR mechanisms requires controlled experimental environments.

Purpose of the Study:

• To elucidate the mechanism behind the NDR effect in 2D TMD devices.
• To demonstrate the role of ambient moisture in achieving a high peak-to-valley current ratio NDR.

Main Methods:

• Experimental investigation of NDR in 2D TMD devices under ambient conditions.
• Utilizing quantum-confined water molecules on 2D TMDs.
• Density Functional Theory (DFT) simulations to corroborate the proposed mechanism.

Main Results:

• Observed NDR with a high peak-to-valley current ratio and proton-diffused superionic conductivity.
• Demonstrated the crucial role of ambient moisture, independent of the 2D TMD material.
• Identified proton migration and interfacial Schottky barrier as key factors in NDR.

Conclusions:

• Ambient moisture is essential for the observed robust NDR effect in 2D TMDs.
• The mechanism involves superionic protonic conduction facilitated by water molecules bonded to sulfur defects.
• Fermi level pinning at the interface influences the Schottky barrier, leading to current restriction at higher biases.