Figure 1.

(a) Schematic description of Self-Organized Metasurface (SOM). (b) Scanning electron micrograph of the SOM is shown (Scale bar 200 nm). The Ag nanoislands are formed due to de-wetting and spontaneous segregation, with approximately 30 nm diameter and 10 nm thicknesses, separated from a continuous Ag film by a 10–20 nm thick dielectric layer (Al₂O₃). (c) Field profiles show confinement and relative enhancement of field along the surface cross-section (scale bar 10 nm). (d) Confocal Raman map on SOM treated with 1 μM Methylene Blue shows the high uniformity of enhancement (scale bar 2 μm, Raman intensity integrated between 500 cm⁻¹ to 2000 cm⁻¹). (e) Computational modeling allows calculation of the peak enhancement factor for the configuration in (c) (40 nm Ag islands with 10 nm spacing, 10 nm above Ag surface). Experimental data (green curve) is shown for a surface with 20 nm dielectric thickness. (f) The resonance wavelength can be tuned by altering the dielectric thickness during fabrication. As the dielectric thickness increases, a broad resonance around 600 nm remains. A large dielectric thickness approximates the limit case of free standing Ag nanoisland film supported by a dielectric sample or substrate.