Adsorption of Ag, Au, Cu, and Ni on MoS2: theory and experiment.

Abstract

Here, we present results of a computational and experimental study of adsorption of various metals on MoS₂. In particular, we analyzed the binding mechanism of four metallic elements (Ag, Au, Cu, Ni) on MoS₂. Among these elements, Ni exhibits the strongest binding and lowest mobility on the surface of MoS₂. On the other hand, Au and Ag bond very weakly to the surface and have very high mobilities. Our calculations for Cu show that its bonding and surface mobility are between these two groups. Experimentally, Ni films exhibit a composition characterized by randomly oriented nanoscale clusters. This is consistent with the larger cohesive energy of Ni atoms as compared with their binding energy with MoS₂, which is expected to result in 3D clusters. In contrast, Au and Ag tend to form atomically flat plateaued structures on MoS₂, which is contrary to their larger cohesive energy as compared to their weak binding with MoS₂. Cu displays a surface morphology somewhat similar to Ni, featuring larger nanoscale clusters. However, unlike Ni, in many cases Cu exhibits small plateaued surfaces on these clusters. This suggests that Cu likely has two competing mechanisms that cause it to span the behaviors seen in the Ni and Au/Ag film morphologies. These results indicate that calculations of the initial binding conditions could be useful for predicting film morphologies. In addition, out calculations show that the adsorption of adatoms with odd electron number like Ag, Au, and Cu results in 100% spin-polarization and integer magnetic moment of the system. Adsorption of Ni adatoms, with even electron number, does not induce a magnetic transition.