Reflectance and surface enhanced Raman scattering (SERS) of sculptured silver films deposited at various vapor incident angles

By using e-beam evaporation at various oblique angles, silver nanorod arrays were produced on silicon and fused silica substrates. Reflectance of P and S polarizations was measured at an incident angle of 30°, with the data analyzed by using the appropriate optical dispersive model. The surface enhanced Raman scattering (SERS) was investigated using trans-1,2-bis(4-pyridyl)ethene (BPE) as a probe molecule at an excitation wavelength of 633 nm. The Ag-coated surface become rougher as the vapor incident angle is increased. Only the sample deposited at 85° shows clear oblique column structure. Reflectance fitting confirmed the positive rexlation between roughness and deposition angle and showed an increase of porosity in the film with increasing deposition angle. The reflectance measurements also indicate that the sample deposited at 85° has a very high anisotropic effect due to the inclined column structure. In the RS scans, only the 85° samples on Si and silica substrates gave strong SERS with a similar enhancement factor, with a higher background level and noise signal from the silica substrate.