Coherently Embedded Ag Nanostructures in Si: 3D Imaging and their application to SERS

Surface enhanced Raman spectroscopy (SERS) has been established as a powerful tool to detect very low-concentration bio-molecules. One of the challenging problems is to have reliable and robust SERS substrate. Here, we report on a simple method to grow coherently embedded (endotaxial) silver nanostructures in silicon substrates, analyze their three-dimensional shape by scanning transmission electron microscopy tomography and demonstrate their use as a highly reproducible and stable substrate for SERS measurements. Bi-layers consisting of Ag and GeOx thin films were grown on native oxide covered silicon substrate using a physical vapor deposition method. Followed by annealing at 800 degrees C under ambient conditions, this resulted in the formation of endotaxial Ag nanostructures of specific shape depending upon the substrate orientation. These structures are utilized for detection of Crystal Violet molecules of 5 x 10(-10) M concentrations. These are expected to be one of the highly robust, reusable and novel substrates for single molecule detection.