Fabrication of surface-enhanced Raman scattering substrate using black silicon layer manufactured through reactive ion etching

In this study, Ag was deposited to investigate its applicability as a surface-enhanced Raman scattering substrate after forming a grasstype black silicon structure through maskless reactive ion etching. Grass-structured black silicon with heights of 2–7 μm was formed at radio-frequency (RF) power of 150–170W. The process pressure was 250mTorr, the O2/SF6 gas ratio was 15/37.5, and the processing time was 10–20 min. When the processing time was increased by more than 20 min, the self-masking of SixOyFz did not occur, and the black silicon structure was therefore not formed. Raman response characteristics were measured based on the Ag thickness deposited on a black silicon substrate. As the Ag thickness increased, the characteristic peak intensity increased. When the Ag thickness deposited on the black silicon substrate increased from 40 to 80 nm, the Raman response intensity at a Raman wavelength of 1507/cm increased from 8.2 × 103 to 25 × 103 cps. When the Ag thickness was 150 nm, the increase declined to 30 × 103 cps and showed a saturation tendency. When the RF power increased from 150 to 170 W, the response intensity at a 1507/cm Raman wavelength slightly increased from 30 × 103 to 33 × 103 cps. However, when the RF power was 200 W, the Raman response intensity decreased significantly to 6.2 × 103 cps.