The effect of layer absorbance for complex surface enhanced Raman scattering substrates

The "hot spots" mechanism is a common wisdom for surface enhanced Raman scattering (SERS). We argue that this is true when the hot spots are directly exposed to the detector. For complex SERS substrates with layered structures such as nanorod arrays, the structure and the layer absorbance both play important roles, which make the effect of hot spots less significant. Using a numerical calculation of the local electric field distribution of an Ag nanorod array substrate, we demonstrate that the layer absorbance must be considered in order to obtain polarization-dependent SERS intensity that is consistent with experimental data.