Modeling and experimental investigations of nanostructured Ag thin films produced by oblique-angle deposition and its SERS performance

The growth mechanism of nanocolumnar silver thin film deposited on a smooth silicon substrate using electron beam evaporation process at an oblique angle was simulated with the Kinetic Monte Carlo method. Following the simulated silver nanostructured thin film, a further computational simulation was done using COMSOL for surface-enhanced Raman scattering effects. The simulation results were compared against corresponding experimental results, which demonstrated high agreement between simulation results and experimental data. It was found that as the incident deposition angle increased, the density of the Ag thin film significantly decreased and the surface roughness increased. When the incident deposition angle was at 75^◦ and 85^◦, the resulting nanocolumnar structure was significantly tilted. For Ag thin films deposited at all investigated angles, surface-enhanced Raman scattering effects were observed. Particularly, the Ag nanocolumns deposited at 85^◦ showed remarkable Surface-enhanced Raman Scattering effects. This was seen in both COMSOL simulations and experimental results: Enhancement factors were 2 × 10⁷ in COMSOL simulation and 3.3 × 10⁵ in the experiment.