Adsorption Behavior of the Hydroxyl Radical and Its Effects on Monolayer MoS2

Based on first-principles density functional theory calculations, we investigated a modified routine using hydroxyl adsorption that recently demonstrated the controlled growth of MoS 2 monolayers. The new growth approach impedes the deposition of a second MoS 2 layer; however, the hydroxyl adsorption and its effects have been mostly unexplored. Through this study, we first explored the adsorption behaviors of the hydroxyl radical (OH) on monolayer MoS 2 and briefly discussed its effects on the stability and electronic structure. Monolayer MoS 2 repels charged OH - , whereas the adsorption of the neutral OH radical is energetically favorable; the corresponding adsorption energies are 0.09 eV and -1.35 eV, respectively. The diffusion barrier of the OH radical on MoS 2 is 0.52 eV, indicating that the molecule can quickly diffuse. Next, the study demonstrated that for multiple OH adsorptions, a concerted reaction including OH dissociation and H 2 O formation is more energetically favorable than the adsorption of two OH molecules by 2.50 eV, which in turn results in a mixed adsorption configuration of O and OH. In addition, we revealed that the OH adsorption creates a mid-gap state and facilitates the reconstruction of the MoS 2 edge.