SERS activity of silver and gold nanostructured thin films deposited by pulsed laser ablation

The deposition power dependence of visible transmittance and refractive index of room temperature-deposited ZnO:Al thin films by RF magnetron sputtering has been studied. All films exhibited high visible transmittance and near-complete UV absorption. The refractive index of the films decreased continuously with an increase in the RF power at all photon energies in the visible and near-IR region, which has been partially attributed to the decreased packing density of the films. For each film, the refractive index exhibited strong frequency dispersion in the weak-absorption region. The origin of optical dispersion at different RF power has been discussed in the light of a single-oscillator model.