Limiting Domain Size of MoS2: Effects of Stoichiometry and Oxygen

Reactive molecular dynamics simulations of MoS 2 crystallization from amorphous precursor materials showed that crystal domain size decreased because of excess S or O, relative to the stoichiometric case. Simulation results were corroborated by comparison of calculated limiting domain sizes to experimental measurements of MoS 2 crystals grown from thermal decomposition of molybdenum dithiocarbamate. Then, the simulations were used to evaluate two previously proposed domain growth mechanisms—thermodynamic and kinetic; both were shown to contribute to MoS 2 domain growth and, importantly, to stopping growth at a limiting size. It was shown that S-rich or O-containing precursor materials can inhibit grain growth (i) thermodynamically, by increasing the amount of S at domain edges which decreases boundary energy, making them more stable and lowering the driving force for growth, and (ii) kinetically, by decreasing the probability of Mo–S interactions at domain edges that would otherwise contribute to domain growth. The simulations explain how each of these mechanisms determines the effect of precursor composition on MoS 2 domain size and, further, suggest avenues for tunable MoS 2 synthesis to achieve application-specific domain size.