Transition Metal Dichalcogenide MoS${}_2$: oxygen and fluorine functionalization for selective plasma processing

TL;DR

This study uses ab-initio molecular dynamics to show that oxygen and fluorine functionalization of MoS₂ significantly lowers sulfur sputtering energy thresholds, enabling more selective plasma processing.

Contribution

It demonstrates that functionalization widens the ion energy window for chalcogen removal, improving control in TMD plasma processing.

Findings

Functionalization lowers sulfur sputtering energy from ~30 eV to ~10 eV.

Cryogenic temperatures significantly affect sputtering thresholds.

The mechanistic theory predicts similar effects in other TMDs and surface impacts.

Abstract

Low-temperature plasma processing is a promising technique for tailoring transition metal dichalcogenides (TMDs). For chalcogen substitution processing, a key challenge is to identify the ion energy window that enables selective chalcogen removal while preserving the metal lattice. Using ab-initio molecular dynamics (AIMD), we demonstrate that oxygen and fluorine functionalization widen the processing window by significantly lowering the sulfur sputtering energy threshold ($E_{\text{sputt,S}}$) of MoS${}_2$ from $\sim 30$ eV to $\sim 10$ eV via formation of sputtering products such as SO${}_2$ and SF${}_n$. Additionally, we show that experimentally relevant cryogenic temperatures strongly affect $E_{\text{sputt,S}}$. The dependence is confirmed via AIMD and also predicted by a mechanistic parameter-free theory, suggesting that $E_{\text{sputt}}(T)$ generalizes to other TMDs, functionalization, and surface impacts in general. Our results highlight oxygen/fluorine functionalization, ionic impact angle, and material temperature to be key control parameters for selective, damage-controlled chalcogen removal in TMD processing.