The optical properties of Cu-Ni nanoparticles produced via pulsed laser dewetting of ultrathin films: The effect of nanoparticle size and composition on the plasmon response

Thin film Cu-Ni alloys ranging from 2-8 nm were synthesized and their optical properties were measured as-deposited and after a laser treatment which dewet the films into arrays of spatially correlated nanoparticles. The resultant nanoparticle size and spacing are attributed to a laser induced spinodal dewetting process. The evolution of the spinodal dewetting process is investigated as a function of the thin film composition which ultimately dictates the size distribution and spacing of the nanoparticles. The optical measurements of the copper rich alloy nanoparticles reveal a signature absorption peak suggestive of a plasmon peak that red-shifts with increasing nanoparticle size and blue-shifts and dampens with increasing nickel concentration.