High-density periodic arrays of self-aligned subwavelength nanopyramids for surface-enhanced Raman spectroscopy

Novel nanotextured surfaces are presented with periodically self-aligned subwavelength nanogroove and nanopyramid structures with precisely defined pitch lambda(g) that are closely packed with 2 nm separation gaps over large areas and form high-density arrays of hot-spot scattering sites ideally suited for surface-enhanced Raman scattering (SERS) and Raman spectroscopy. The simple self-aligning fabrication technique requires only a single lithography step and wet anisotropic etching. Measured average Raman enhancement factors of G approximate to 10(6) from rhodamine 60 (R6G) on patterned Au surfaces with lambda(g) = 200 nm are consistent with numerical calculations. The nanostructured surfaces can be scaled to smaller dimensions, which results in increased enhancement as well as increased hot-spot spatial density.