Simple model for surface-enhanced Raman scattering from tilted silver nanorod array substrates

A modified Greenler’s model is proposed to interpret surface enhanced Raman scattering (SERS) for molecules adsorbed onto a tilted and aligned Ag nanorod array substrate. This model only considers molecules absorbed on the side walls of the nanorods and the Raman incident and collection configurations. It reveals that when the incident angle increases to an optimal angle, the SERS intensity reaches a maximum. With the increase in the nanorod tilting angles, the maximum SERS intensity almost does not change, but the optimal incident angle increases linearly. The underlayer thin film also plays an important role for SERS enhancement. In addition, the SERS intensity is closely related to the polarization of the excitation light. When the incident angle is smaller than 15°, s polarization excites stronger Raman signals; at other incident angles, p-polarization excitation contributes more Raman intensity. Those theoretical predictions are qualitatively consistent with our experimental observations.