Tuning Electrical Conductance of MoS₂ Monolayers through Substitutional Doping

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanoscience

Background:

• Substitutional doping is key for tuning semiconductor conductivity in devices.
• Controlling dopant concentration and isolating their impact in 2D materials remains challenging.
• Unintentional doping during fabrication often complicates studies of 2D material properties.

Purpose of the Study:

• To achieve controlled substitutional doping in wafer-scale molybdenum disulfide (MoS2) monolayers.
• To investigate the direct electrical impact of dopants in MoS2 monolayers, separate from fabrication effects.
• To explore the potential of doped MoS2 as stable building blocks for electronic circuitry.

Main Methods:

• Wafer-scale growth of continuous MoS2 monolayers with tunable niobium (Nb) and rhenium (Re) concentrations.
• Fabrication of MoS2 devices using a polymer-free approach to ensure purity.
• Electrical characterization to measure conductivity changes with varying dopant levels.

Main Results:

• Reproducible tuning of MoS2 electrical conductivity over seven orders of magnitude by controlling Nb concentration.
• Observation that dopant carriers exhibit incomplete ionization in 2D MoS2, differing from 3D materials.
• Demonstration of stable dopants, allowing processed MoS2 films to serve as independent electrodes.

Conclusions:

• Controlled substitutional doping is feasible in 2D MoS2, enabling significant conductivity modulation.
• Incomplete carrier ionization in 2D materials is attributed to weaker charge screening and impurity band conduction.
• Stable, doped MoS2 monolayers can be utilized as functional components in advanced electronic circuits.