Highly effective SERS substrates based on an atomic-layer-deposition- tailored nanorod array scaffold

When two metallic surfaces supporting plasmonic excitation are brought into close proximity of each other, a nanogap (of width on the subwavelength scale) will form, which boosts greatly the local optical field. Based on this idea, we fabricated two types of three-dimensional plasmonic substrates with such nanogaps, taking advantage of both atomic layer deposition (ALD) and the capillary effect. Owing to the counteraction of the gap-reducing and capillary, nanogaps with different widths and profiles have been formed on the scaffold of aligned ZnO nanorods and shown to induce large field enhancement with enhancement factor up to 2.64 × 10⁶ for surface-enhanced Raman scattering (SERS).