Figure 2From: SERS substrates formed by gold nanorods deposited on colloidal silica filmsSEM and AFM images of opal-like photonic crystals and the bandgap zone. Respective SEM (a, b) and AFM (c) images of thin (a) and thick (b, c) opal-like photonic crystals formed by depositing 200-nm silica spheres by spin coating on a silicon substrate. (d) The bandgap zone centered around 500 nm as revealed from the reflectance spectrum.Back to article page