Formation of the core-shell structures from bimetallic Janus-like nanoclusters under low-energy Ar and Ar13 impacts: A molecular dynamics study

Abstract

Using the molecular dynamics method, 100 and 500 ps evolutions of 390-atom Cu-Au and Cu-Bi free clusters under 0.05–1.4 keV Ar1 and Ar13 projectiles’ bombardment are simulated. Initial clusters have the Janus-like metastable construction of two mono-component parts with their insignificant overlap. Excluding low energy impacts, Ar13 projectiles induce a few times higher temperatures in the clusters and an order of the magnitude larger sputtering yields with a contribution of the thermal mechanism than Ar particles do. In both clusters, Cu atoms show the resultant trend of displacements into the cluster depth, while Au and Bi atoms tend to increase their near-surface concentrations that lead to various distributions of the components depending on external conditions. In particular, at 300 eV Ar13 impacts, an explicit core-shell structure with a mainly copper core coated by a bismuth-enriched near-surface layer in the Cu-Bi cluster is revealed. Along with that, an approximately homogeneous mixture with weak spatially fuzzy segregation of quantitatively dominating Cu atoms inside the Cu-Au cluster and Au atoms in the outer region is formed. At Ar1 impacts, transfer of atoms is less intense and leads to eccentric arrangements of the copper-enriched core in the Cu-Bi cluster and an inhomogeneous mixture in Cu-Au cluster with still higher inner gold concentration despite the relocation trends.