Atomically Resolved Defects Modulate Electronic Structure in Plasma-Assisted 2D Janus MoSSe Monolayers.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Janus transition metal dichalcogenides (TMDs) show promise for next-generation electronics.
• Real-world device performance of Janus TMDs often falls short of theoretical predictions.
• The atomic-scale origins of these performance discrepancies remain largely unexamined.

Purpose of the Study:

• To provide atomic-scale insights into the electronic structures of monolayer Janus Molybdenum Sulfide Selenide (MoSSe).
• To identify and characterize defect species influencing device performance in Janus MoSSe.
• To elucidate the link between atomic imperfections and macroscopic device limitations.

Main Methods:

• Scanning tunneling microscopy (STM).
• Scanning tunneling spectroscopy (STS).
• Atomic-scale defect characterization.

Main Results:

• Identified residual sulfur dopants creating shallow in-gap states (≈0.5 eV) near the valence band.
• Discovered two distinct native charge defects with electronic influence extending ≈2.5 nm.
• Observed conductive charge traps reducing the local effective bandgap by over 50% and insulating scattering centers hindering carrier transport.

Conclusions:

• Atomic-scale imperfections critically govern the electronic properties of monolayer Janus MoSSe.
• Understanding these defects provides fundamental design criteria for improving Janus electronic devices.
• This work bridges the gap between atomic-scale understanding and macroscopic device limitations.