Controlling sputtering energy threshold in MoS2 TMD plasma processing via surface functionalization

Transition metal dichalcogenide-s (TMDs) are a novel class of quasi-2D materials with potential applications in smaller semiconductor chips, nanoscale piezoelectric biosensing, and more. However, their manufacturing consists of many steps and poses various currently unsolved challenges. 

In this work, we focus on computationally analysing low-energy plasma-assisted desorption/etching of MoS₂ as one of the manufacturing stages. First, we systematically choose the level of theory and use a combination of equilibrium and non-equilibrium ab-initio molecular dynamics simulations to identify geometrical regions of MoS₂ most susceptible to damage from plasma particles. We provide energy thresholds for sputtering and investigate their angular behaviour. We show how oxidation and fluorination of MoS₂ can lower the sputtering energy thresholds, thus expanding the energy range where plasma is expected to desorb the targeted TMD top layer without damaging the metal scaffold. We find a novel temperature dependence of the sputtering threshold of MoS₂O. We propose a multistage sputtering mechanism that explains this new trend, and we confirm it in simulations.

Our findings suggest that both oxygen and fluorine functionalizations can significantly decrease the sputtering energy thresholds of MoS₂. Additionally, MoS₂O and MoS₂F thresholds react differently to temperature and impact angle, making these controls a potential way to achieve precise and selective etching.