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 Pd-n (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 Pd-n 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 Pd-5 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.