Ligand induced structure and property changes of 1T-MoS₂

Stabilizing metastable 1T-MoS₂ sheets is significant for their potential applications. In this work, we investigate the influence of surface adsorption of a series of functional groups (including -H, -O, -SH, -NH₂, -CH₃, -CF₃, -SCH₃ and -OCH₃) on the structural and electronic properties of 1T-MoS₂ by using first-principles calculations. Strong adsorptions of these functional groups eventually transform 1T-related MoS₂ monolayers into the 1T′ phase (featuring zigzag Mo-Mo chains). The adsorptions of functional groups on 1T′-MoS₂ monolayers highly prefer half of the surface sites (the S_t sites) and try to form adsorbate pairs at the S_t sites of the second nearest neighbors, which means that the study of surface-decorated 1T′-MoS₂ monolayers should not be based on randomly generated configurations. Factors like the type of functional group as well as its coverage and configurations make the relationship between the structure of the adsorbate-MoS₂ complex and its electronic properties (e.g. band gap) unclear, which implies that the band gap engineering through surface adsorption is unpredictable.