**4.2.1 Electroless grown silver nanograins**

The electroless growth is a process whereby ionic silver is reduced and deposited as metallic silver upon silicon, via a redox reaction, and according to a mechanism that may be adequately described by a diffusion limited aggregation model. A satisfactory comprehension of the method may be found in (Coluccio et al., 2009). Here it is briefly recalled that, conveniently employing this process, and depending upon the growth parameters, silver nanograins may be obtained with an average size as small as few tens of nanometers, which compose efficient SERS substrates (Fig. 4.4A).

Fig. 4.4. SEM images of a metallic photonic crystal and plasmonic device.
