Controlling MoS₂ Nanosheet Size and Network Conductivity through Alkylammonium Ion Selection

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Solution-processed two-dimensional (2D) semiconductors like molybdenum disulfide (MoS2) are key for low-cost printed electronics.
• High-aspect-ratio nanosheets are crucial for achieving low-resistance junctions and optimal network conductivity.
• Electrochemical exfoliation using ammonium salts is a promising method for producing these nanosheets, but process parameters need further investigation.

Purpose of the Study:

• To systematically investigate the influence of alkylammonium ion size on the electrochemical exfoliation of MoS2.
• To control the dimensions (length and thickness) of MoS2 nanosheets produced.
• To correlate nanosheet dimensions and aspect ratio with the electrical conductivity of fabricated networks.

Main Methods:

• Electrochemical exfoliation of MoS2 using alkylammonium salts of varying sizes.
• Characterization of MoS2 nanosheet dimensions (length, thickness) and aspect ratios.
• Fabrication and electrical characterization of nanosheet networks to determine conductivity.

Main Results:

• Demonstrated control over MoS2 nanosheet lengths (1-3 μm) and thicknesses (1-4 nm) by varying alkylammonium ion size.
• Achieved high nanosheet aspect ratios (kNS) ranging from 400 to 2500.
• Fabricated networks from higher-aspect-ratio nanosheets exhibited significantly improved conductivity, reaching up to 6000 Sm⁻¹.

Conclusions:

• Nanosheet aspect ratio, controlled by ion size during electrochemical exfoliation, directly impacts network conductivity.
• Network conductivity is limited by internanosheet junction resistance, which scales inversely with nanosheet area.
• Optimizing ion size offers a pathway to engineer MoS2 nanosheet dimensions for enhanced performance in printed electronic applications.