Enhanced Raman Scattering from ordered vertical silicon nanowires array

Silicon nanowires array coated with silver nanoparticles as a sensitive Surface-enhanced Raman scattering system could detect R6G molecules up to 10e-14 M and achieve enhancement factor of 108. However, the reproducibility of such system was poor possibly due to the disorder of the silicon nanowires and silver nanoparticles.Herein, we used polystyrene nanospheres monolayer as mask and metal-catalytic chemical etching to make large-area ordered vertical silicon nanowires array with controllable diameters, spacing and lengths. The spontaneous Raman scattering of this system was more than ten times larger than that of the bulk silicon, and the enhancement increased with decreasing diameter and length. The origin of the enhancement may be the light scattering resonance that built up high-field intensities inside the nanowires.This system can be a promising candidate in lowering the threshold of the silicon Raman laser, and the fabrication method is easy and inexpensive compared to deep reactive ion etching in making vertical silicon nanowires.