Investigation of Black Silicon As SERS Substrate for High Sensitivity Detection

Surface enhanced Raman scattering (SERS) has been utilized for bio-detection, environmental monitoring, single molecule detection and toxic material analysis. Various SERS substrates such as silver coated nano sphere array, gold or silver nano particles cluster and electrochemically roughened metallic surface have been fabricated and the enhancement effect has been examined. In this study, we have investigated the effect of the surface morphology of the black silicon substrate on SERS. The ratio of O₂/SF₆ flow rate was adjusted to produce the black silicon with different tip densities (tip numbers per unit area). It was found that the higher the tip density, the greater the ehancement effect. Moreover, by increasing the thickness of the deposited gold layer on the black silicon substrate, the SERS effect can be increased as well. This could be owing to generation of more hot spots by bridging individual silicon tips through the thick gold deposit. The detection limit of 10fM R6G solution with uniform SERS effect across the SERS substrate was achieved. The single algal cell will be analyzed and the SERS spectrum will be acquired by using the black silicon substrate as fabricated.