Formation and Characterization of Femtosecond-Laser-Induced Subcluster Segregated Nanoalloys

We report the first synthesis of subcluster segregated nanoalloys formed through the joining of immiscible metallic nanoparticles (NPs) using femtosecond (fs) laser irradiation. Immiscible alloy components consisting of Ag and Ni, and Ag and Fe, all in the form of NPs, were first deposited on a carbon film in vacuum by fs laser ablation from the parent metals. These samples of randomly distributed NPs were then irradiated with multiple fs laser pulses at a fluence of 1.5 mJ/cm2. Transmission electron microscopy (TEM) observations indicate that Ag and Ni as well as Ag and Fe NPs were successfully joined under these conditions. Energy dispersive X-ray (EDX) results show that no mixing layer exists at the interface. The nanostructure in the interface reveals the assumption of a specific angle between two matching planes on either side of the interface. Calculation of the lattice mismatch indicates that the system adjusts to this angle so as to reduce surface energy. Structural ledges were also formed at the interface to further compensate for the atomic misfit.