Transition from discrete patches to plasmonic nanohole array by glancing angle deposition on nanosphere monolayers.

By combining nanosphere lithography and glancing angle deposition, a morphological transition from disconnected patchy silver (Ag) coated nanosphere particles to a connected Ag nanohole sheet on close-packed nanosphere monolayers has been demonstrated, which significantly changes the optical property of the Ag nanostructure deposited. For different sized nanosphere monolayers, when the vapor incident angle was set to be 55o, the transmission spectra showed complicated features when the Ag deposition thickness was less than 60 nm. When the thickness was large enough ( 60 nm), a distinguished extraordinary optical transmission (EOT) peak was observed. The EOT peak wavelength position is independent of the Ag thickness deposited and is proportional to the nanosphere diameter. The obtained EOT peaks possess a high quality factor and have high transmission values compared to those reported in the literature for similar structures. The Monte Carlo growth simulations demonstrate the morphological transition from the patchy arrays to nanohole arrays while the electromagnetic numerical calculations confirm the change in the optical properties. Such a high quality EOT response could be used for constructing better sensors or developing other plasmonic applications.