Edge-structure dependent growth mechanism. (A) DFT calculations of the free energy for MoS₂ growth with and without iodine assisting under near equilibrium S-rich condition. (B) DFT calculation of the nucleation energy for different halogen elements under near equilibrium S-rich condition. (C) TEM image of the as-grown MoS₂. (D) The corresponding SAED pattern of (C). (E) A line profile through the measured diffraction spots in (D). The higher intensity k_b spots towards the Mo sublattice, as indicated by the arrows in (C) and (D). (F) Diagram of large MoS₂ domains with S-terminated edges vs. Mo-terminated edges.