Disordered films were prepared by drop-casting AuNFs onto Si substrates and drying the samples for at least 3 h at room temperature. The substrates were cleaned using UV-ozone plasma cleaning for 30 min, followed by washing in ethanol and water. The films show a high particle density with no regular structure (Figure ). After drop-casting, we cleaned the samples of any residuals by 60 min UV-ozone plasma cleaning. Previous experiments demonstrated a strong surface enhancement for Raman scattering (SERS) on these types of samples, pointing to the presence of regions with high field enhancements (Figure ).