Controlling the alloy composition of PtNi nanocrystals using solid-state dewetting of bilayer films

We demonstrate that solid-state dewetting of bilayer films is an effective way for obtaining bimetallic alloy nanocrystals of controlled composition. When a Pt-Ni bilayer film were annealed near 700 °C, Pt and Ni atoms inter-diffused to form a PtNi bimetallic alloy film. Upon annealing at higher temperatures, the bilayer films transformed into <111> oriented PtNi alloy nanocrystals in small-rhombicuboctahedron shape through solid-state dewetting process. The Pt content of the nanocrystals and the alloy films, estimated by applying the Vegard's law to the relaxed lattice constant, was closely related to the thickness of each layer in the as-grown bilayer films which can be readily controlled during bilayer deposition.