Designing barrier-free metal/MoS₂ contacts through electrene insertion

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Transition-metal dichalcogenides (TMDCs), such as MoS2, show promise for electronics but suffer from performance limitations due to high-resistance metal contacts.
• Fermi-level pinning and tunnelling barriers at the TMDC-metal interface impede efficient charge transfer in nanodevices.

Purpose of the Study:

• To investigate the potential of alkaline-earth sub-pnictide electrenes ([M2X]+e-, M = Ca, Sr, Ba; X = N, P, As, Sb) as an interfacial layer to overcome contact resistance issues in TMDCs.
• To identify optimal material combinations for low-resistance Ohmic contacts between metals (Au, Cu) and MoS2 using electrene interlayers.

Main Methods:

• Density-functional theory (DFT) calculations were employed to model metal/electrene/MoS2 heterojunctions.
• Analysis included computation of charge transfer, band structure, and electrostatic potential to assess contact properties.
• Investigated all stable M2X electrenes interfaced with Au and Cu metals and MoS2.

Main Results:

• Electrene monolayers effectively donate surface charge to MoS2, lowering its conduction band edge and mitigating Schottky and tunnelling barriers.
• Linear correlations were established between charge donation, electrene surface charge, and work function.
• Ca2N demonstrated the highest potential for facilitating Ohmic contact due to its significant surface charge density.

Conclusions:

• Alkaline-earth sub-pnictide electrenes offer a viable strategy for engineering low-resistance Ohmic contacts to TMDCs.
• The Ca2N electrene is identified as a particularly promising candidate for improving MoS2-based electronic device performance.
• This approach addresses a critical bottleneck in the application of 2D materials in advanced electronics.