Effect of particle shape distribution on the surface plasmon resonance of Ag SiO2nanocomposite thin films

Silver–silica nanocomposite thin films were prepared by high pressure d.c. sputtering technique. Films deposited at lower substrate temperature showed a narrow distribution of nanoparticles with nearly spherical shape. Increase in substrate temperature resulted in films with a non-uniform size and shape due to the agglomeration of the nanoparticles. This size and shape distribution has a profound effect on the optical absorbance spectra and results in a broad and asymmetric surface plasmon band. A shape distribution introduced in the Maxwell–Garnett or Bruggeman effective medium theory was found to give a reasonable description of the experimentally observed optical absorption spectra.