Surface‐enhanced Raman scattering sensing on black silicon

Abstract

Reactive ion etching was used to fabricate black-Si over the entire surface area of 4-inch Si wafers. After 20 min of the plasma treatment, surface reflection well below 2% was achieved over the 300-1000 nm spectral range. The spikes of the black-Si substrates were coated by gold, resulting in an island film for surface-enhanced Raman scattering (SERS) sensing. A detection limit of 1 × 10 −6 M (at count rate > 10 2 s −1 . mW −1 ) was achieved for rhodamine 6G in aqueous solution when drop cast onto a ∼ 100-nm-thick Au coating. The sensitivity increases for thicker coatings. A mixed mobile-on-immobile platform for SERS sensing is introduced by using dog-bone Au nanoparticles on the Au/black-Si substrate. The SERS intensity shows a non-linear dependence on the solid angle (numerical aperture of excitation/collection optics) for a thick gold coating that exhibits a 10 times higher enhancement. This shows promise for augmented sensitivity in SERS applications.

Anti-reflective surfaces: Cascading nano/microstructuring

“…It was previously demonstrated how inductively coupled plasma reactive ion etched (ICP-RIE) b-Si with plasmonic nanoparticles can be used as a highly effective absorber for photo-thermoelectric conversion applications. 20 Nanospikes of b-Si coated with Au have shown high performance when used in surface-enhanced Raman spectroscopy/scattering (SERS) 21 and were also proven to be bactericidal through the mechanical destruction of bacterial membranes. 22 Using a simple chemical treatment in either gas phase or solution, these nanotextured surfaces can also be rendered super-hydrophobic.…”

Engineering gold alloys for plasmonics

“…This, most probably, is caused by the chemical effect in the SERS enhancement mechanism providing new method to facilitate molecular recognition and finger printing which is highly required for complex molecules and solutions. Alloys of noble metals can be used on largesurface-area photo-electrodes and sensors such as black Si [21,22].…”

Plasmonic photo-thermoelectric energy converter with black-Si absorber

“…Heat transport to the hot Seebeck electrode and temperature gradients in b-Si can be further optimized with thinner b-Si. Optical, thermal, and bactericidal [25] and hydrophobic properties of b-Si are expected to be used in number of applications from solar cells [26] to sensing [14,15].…”

“…6(c) generate extremely high intensity hot spots, which in turn lead further enhancement of absorbtion. This phenomenon works to locally boost absorption much in the same way as hot spots on Au coated b-Si further enhance light concentration required for surface enhanced Raman scattering (SERS) [14,15]. Fig.…”