Atomic-scale phase separation induced clustering of solute atoms

Dealloying typically occurs via the chemical dissolution of an alloy component through a corrosion process. In contrast, here we report an atomic-scale nonchemical dealloying process that results in the clustering of solute atoms. We show that the disparity in the adatom–substrate exchange barriers separate Cu adatoms from a Cu–Au mixture, leaving behind a fluid phase enriched with Au adatoms that subsequently aggregate into supported clusters. Using dynamic, atomic-scale electron microscopy observations and theoretical modeling, we delineate the atomic-scale mechanisms associated with the nucleation, rotation and amorphization–crystallization oscillations of the Au clusters. We expect broader applicability of the results because the phase separation process is dictated by the inherent asymmetric adatom-substrate exchange barriers for separating dissimilar atoms in multicomponent materials.
Dealloying usually relies on chemical dissolution of an alloy component. By contrast, the authors demonstrate an atomic-scale phase separation process that differs completely from the chemical dealloying mechanism and thus represents a significant departure from the well-known Hume-Rothery rules.