Evolution of the localized surface plasmon resonance and electron confinement effect with the film thickness in ultrathin Au films

Localized surface plasmon resonance (LSPR) and electron confinement effects on the interband transitions and free-electron absorption in ultrathin Au films with the film thicknesses of about 1-12 nm are investigated. A significant evolution of the LSPR, interband transition energies, plasma energy, and conductivity with the film thickness is observed. The evolution is attributed to the changes in the size, shape, and spacing of the self-assembled gold nanoparticles (Au NPs) with the sizes from several nanometers to 110 nm as well as the aggregation of the Au NPs in the Au films.