Au cluster adsorption on perfect and defective MoS₂ monolayers: structural and electronic properties

The adsorption of Aun (n = 1-4) clusters on perfect and defective MoS₂ monolayers is studied using density functional theory. For the pristine MoS₂ monolayer, our results show that the electrons are transferred from the support to the adsorbed Au clusters, thus a p-doping effect is achieved in the pristine MoS₂ monolayer by the Au cluster adsorption, which is in good agreement with the experimental findings. The adsorption of Au clusters can introduce mid-gap states, which modify the electronic and magnetic properties of the systems. The adsorbates containing an odd number of Au atoms can introduce a spin magnetic moment of 1 μB into the perfect MoS₂ monolayer, while those systems containing an even number of Au atoms are spin-unpolarized. Two categories of defects, i.e., a single S vacancy and Mo antisite defect with one Mo atom replacing one S atom, are considered for the defective monolayer MoS₂. Compared with the pristine MoS₂ monolayer, the adsorption energies for Au clusters are significantly increased for the MoS₂ monolayer with a single S vacancy, and there are more electrons transferred from the MoS₂ monolayer with an S vacancy to the Au clusters. The mid-gap states and odd-even oscillation magnetic behavior can also be observed when Au clusters are adsorbed on the MoS₂ monolayer with an S vacancy. For those systems of Au clusters on MoS₂ monolayers with Mo antisite defects, the adsorption energies as well as the magnitude and the direction of transferred charge are similar to those for the MoS₂ monolayer with an S vacancy. The spin-polarizations appear in all systems with Mo antisite defects. Our investigations suggest that the electronic and magnetic properties of MoS₂ nanosheets can be effectively modulated by the adsorption of Au clusters.