In Operando Study of Charge Modulation in MoS₂ Transistors by Excitonic Reflection Microscopy

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Optical properties of 2D transition metal dichalcogenides (TMDs) are sensitive to charge density variations.
• Excitons and trions significantly influence the refractive index and extinction coefficient in TMDs.
• Understanding charge carrier behavior is crucial for optimizing 2D material-based electronic devices.

Purpose of the Study:

• To introduce and validate excitonic reflection microscopy (XRM) for imaging electron density in 2D TMD devices.
• To demonstrate the capability of XRM for real-time, wide-field charge distribution mapping in MoS2 field-effect transistors.
• To investigate bias-dependent charge inhomogeneities and resistive delays in 2D materials.

Main Methods:

• Optical interference reflection microscopy utilizing excitonic wavelengths.
• Development and application of XRM for high-throughput imaging.
• Characterization of MoS2 field-effect transistors under varying gate and drain biases.

Main Results:

• XRM provides complete charge distribution maps in MoS2 transistor channels with subsecond throughput.
• The technique achieves imaging speeds approximately three orders of magnitude faster than scanning probe methods like KPFM.
• Real-time mapping of charge inhomogeneities, study of resistive delays in polycrystalline networks, and analysis of bias competition effects were achieved.

Conclusions:

• XRM is a powerful, rapid technique for probing electron density and charge distribution in operating 2D TMD devices.
• The method offers significant advantages for studying dynamic charge behavior, device performance, and material properties.
• XRM enables deeper understanding of charge control mechanisms in advanced 2D electronic devices.