Silicon-Based SERS Substrates Fabricated by Electroless Etching

Surface enhanced Raman scattering has recently been proposed as a label free sensing method for diagnostic applications. Raman scattering is an excellent analysis tool because a wealth of information can be obtained using a single measurement, however the weak signal has made it unsuitable for detecting low concentrations of analytes. Using plasmonic nanostructures to create SERS substrates, the Raman signal can be amplified by several orders of magnitude, but SERS substrates have been complicated to fabricate. Here we report low-cost silicon substrates based on simple fabrication method of silver nanoparticles and silicon nanowires decorated with these nanoparticles for use as a convenient practical platform for SERS-active substrates. In addition, the placement of silver nanoparticles on silicon nanowires allowed the autoaligning of the hot spots such that low cost Raman systems with normal incident laser can be used. These substrates have the ability to detect wide range of concentrations of pyridine, as low as 10(-11) M. An enhancement factor of around 6 to 8 x 10(5) was observed for silver nanoparticles alone. By depositing the same nanoparticles on silicon nanowires, the enhancement factor jumped by orders of magnitude to 10(11).