fano resonances as optical markers of sub-wavelength nanoparticle packaging and elemental segregation in laser-dewetted au-pd film

A 50-nm-thick alloyed gold-palladium film on a silica substrate was dewetted by 1060-nm/ns laser pulses and characterized by scanning electron microscopy. optical transmission spectroscopy of the millimeter-sized spot of the dewetted film demonstrates pronounced fano resonances, typical for large regular arrays of oligomers of plasmonic nanoparticles. the oligomer configuration and almost pure gold composition of the nanoparticles, underlying the spectral fano resonances, were revealed via numerical simulations with the input electron microscopy visualization and hydrogen absorption tests. the promising application of fano resonance for simple optical characterization of ordering or packaging parameters in large-scale arrays of deeply sub-wavelength plasmonic and/or dielectric nano-oligomers was proposed.