Figure 2. Raman spectra of a 40-nm SiO_x film annealed at 1100 °C measured using a 50× objective and 488-nm laser with exposures of 1 s (a) and 600 s (b).

The red curves show the results for the uncoated SiO_x film (no Ag) and blue curves are for the SiO_x film with an Ag overlayer (Ag, weight thickness 12 nm). The Raman band at ~517 cm⁻¹ originates from Si-nc with diameters of 3–4 nm. A broad band for the uncoated film is from the silica substrate. For the spectra in panel b, the linear background is subtracted.