Compact Super Electron-Donor to Monolayer MoS₂

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Surface functionalization of 2D materials is key to tuning electronic properties.
• Organic electron donors (OEDs) are used to achieve this modulation.
• Existing OEDs have limitations in doping efficiency.

Purpose of the Study:

• To introduce a novel molecular dopant, Me-OED, for enhanced doping of MoS₂.
• To investigate the relationship between molecular size, surface coverage, and doping efficiency.
• To achieve record-breaking carrier densities in MoS₂.

Main Methods:

• Synthesis and application of Me-OED and ^tBu-OED molecular dopants.
• Field-effect transistor (FET) measurements to assess carrier density.
• Spectroscopic characterization to analyze doping mechanisms.
• Computational calculations to support experimental findings.

Main Results:

• Me-OED achieved a record carrier density of 1.10 ± 0.37 × 10¹⁴ cm^-2 in MoS₂.
• Me-OED exhibited significantly higher doping power (0.22-0.44 electrons/molecule) compared to ^tBu-OED (0.11 electrons/molecule).
• The compact size of Me-OED was identified as crucial for high surface coverage and effective doping.
• Experimental results were in good agreement with theoretical calculations.

Conclusions:

• The small molecular size of Me-OED is critical for maximizing surface coverage and interaction with MoS₂.
• Me-OED represents a significant advancement in molecular doping of 2D materials.
• This work enables unprecedented doping levels in MoS₂, paving the way for novel electronic devices.