The Modulation Effect of MoS₂ Monolayers on the Nucleation and Growth of Pd Clusters: First-Principles Study.

The geometries, electronic structures, adsorption, diffusion, and nucleation behaviors of Pdn (n = 1⁻5) clusters on MoS₂ monolayers (MLs) were investigated using first principles calculations to elucidate the initial growth of metal on MoS₂. The results demonstrate that Pd clusters can chemically adsorb on MoS₂ MLs forming strong Pd⁻S covalent bonds with significant ionic character. We investigated the initial growth mode of Pd clusters on MoS₂ monolayers and found that Pdn clusters tend to adopt pyramid-like structures for n = 4⁻5 and planar structures lying on MoS₂ substrates for n = 1⁻3. It can be explained by the competition between adsorbate⁻substrate and the intra-clusters' interactions with the increasing coverage. Compared with pristine MoS₂ MLs, the work function was reduced from 5.01 eV upon adsorption of Pd monomer to 4.38 eV for the case of the Pd₅ clusters due to the charge transfer from Pd clusters to MoS₂ MLs. In addition, our calculations of the nucleation and diffusion behaviors of Pd clusters on MoS₂ MLs predicted that Pd is likely to agglomerate to metal nanotemplates on MoS₂ MLs during the epitaxial stacking process. These findings may provide useful guidance to extend the potential technological applications of MoS₂, including catalysts and production of metal thin films, and the fabrication of nanoelectronic devices.