Optical properties of silver nanoparticles deposited onto silicon substrates by different soft-solution processing techniques

Silver nanoparticles have been grown onto crystalline silicon substrates. Three soft-solution one-step processing techniques have been assayed: electroless metal deposition (EMD), electrodeposition (ED) and spray pyrolysis (SP). The shapes exhibited by the silver nanoparticles prepared by EMD and ED are hemispherical, while the shapes of those prepared by SP (for long processing times) are similar to disks of aspect ratio 0.5 approximately. Integrated total reflectance spectra and integrated diffuse reflectance spectra shows distinctive features due to the electronic structure of silicon. Specular reflectance spectra of samples (except those grown by SP with long processing times) show a dip, corresponding to a surface plasmon resonance. Simulations, considering granular composite media were made. The simulated spectra confirm the presence of the spectral dip. Surface plasmon resonance show shifts with the angle of incidence. For samples prepared by ED, the tendency is the same as the one of the model, indicating that there is not much coupling between nanoparticles.