Transition Metal Dichalcogenide MoS₂: Oxygen and Fluorine Functionalization for Selective Plasma Processing

Area of Science:

• Materials Science
• Surface Science
• Plasma Physics

Background:

• Low-temperature plasma processing is vital for modifying transition metal dichalcogenides (TMDs).
• Selective chalcogen removal without damaging the metal lattice is a key challenge in TMD processing.
• Understanding ion energy thresholds is critical for controlled sputtering.

Purpose of the Study:

• To investigate the effects of oxygen and fluorine functionalization on chalcogen sputtering in MoS2.
• To determine the ion energy window for selective sulfur removal.
• To explore the influence of temperature on sputtering dynamics.

Main Methods:

• Ab initio molecular dynamics (AIMD) simulations were employed to model sputtering processes.
• Calculations focused on the sulfur sputtering energy threshold (Esputt,S) of MoS2.
• A mechanistic, parameter-free theory was used to predict temperature dependence.

Main Results:

• Oxygen and fluorine functionalization significantly reduced the sulfur sputtering energy threshold of MoS2 from ~30 eV to ~10 eV.
• Formation of sputtering products like SO2 and SFn was observed.
• Cryogenic temperatures were found to strongly influence the sulfur sputtering energy threshold, a dependence confirmed by AIMD and theory.

Conclusions:

• Oxygen/fluorine functionalization provides a wider processing window for selective chalcogen removal in TMDs.
• Material temperature and ionic impact angle are critical parameters for damage-controlled sputtering.
• The findings generalize to other TMDs, functionalizations, and impact conditions, offering a pathway for precise material tailoring.