Gas-Phase Chemistry of Salt-Assisted MoS₂ Growth

The gas-phase chemistry of salt-assisted MoS₂ growth has been studied using quantum chemical molecular dynamics simulations, with the goal of understanding the effect of alkali metal chloride salts (LiCl, NaCl, KCl) on the initial chemical pathways present during growth. We observe that a novel intermediate structural moiety, Cl-MoO₃-Z (Z = Li, Na, K), forms readily in all simulations with salt. This species persists throughout all simulations, as opposed to other species, such as S-MoO₃-S and S-MoO₃-Na, indicating that it may be a key driver of MoS₂ formation and growth. Salt also significantly reduces sulfur oligomerization kinetics, suggesting the ability for improved control over MoS₂ morphology. Most interestingly, NaCl disrupts MoO₃-MoO₃ network formation and growth that occurs under high precursor densities, leading to higher populations of undercoordinated MoO₃ and a tendency toward 2D networks morphologies, increasing opportunities for Mo sulfurization. These findings were found to be NaCl-concentration-dependent, suggesting another method for controlling the CVD synthesis of MoS₂ via controlling salt concentration in the gas phase.