A simple method of growing endotaxial silver nanostructures on silicon for applications in surface enhanced Raman scattering (SERS)

摘要

Endotaxial structures are related to the growth of precipitate phases in the bulk matrix having a coherent interface with the surrounding. In general, sophisticated physical vapor deposition techniques, like molecular beam epitaxy (MBE) in ultra-high vacuum (UHV) or ion implantation followed by high-temperature annealing are used to grow endotaxial structures. Here, we have shown that a simple electroless deposition followed by rapid thermal annealing process can generate triangular-shaped endotaxial Ag nanostructures along with spherical Ag nanoparticles on the planar silicon surface. Remarkably, compared to only Ag spherical particles, a silicon surface covered with spherical plus triangular-shaped nanoparticles shows significant SERS enhancement revealing the crucial role of the endotaxial triangular Ag nanostructures in SERS. By studying the aging effect, we have demonstrated that embedded triangular endotaxial particles are structurally more stable than the spherical nanoparticles residing on the surface revealing a robust route of fabricating SERS substrate where stability is an important issue. We presume that the nanogaps between the spherical and triangular endotaxial particles act as one of the major sources of "hot spots" where the sharp edges of the triangular geometry pose favorable situation for SERS enhancement observed in the present case.