Femtosecond and nanosecond laser fabricated substrate for surface-enhanced Raman scattering

Surface-enhanced Raman scattering has many applications to chemical science, and shows great promise in the medical field because of its ability to provide molecular fingerprinting of probe molecules, whereby a material can be identified and potentially quantified. This is done by enhancing the normally weak Raman spectrum by many orders of magnitude with the use of fabricated substrates. It is therefore desirable to produce repeatable substrates with high enhancement factors for identification and quantification of samples. This thesis introduces a new method for generating such a substrate. By using femtosecond laser machining, gold sputtering, and nanosecond laser annealing, gold nanoparticles were created on the surface of a silicon wafer. SEM images of the substrate are taken to examine the substrate surface generated by the different processing stages. This method of fabrication is both fast and highly repeatable, while at the same time providing high enhancement factors. Using a He-Ne laser with a 632.8 nm wavelength, enhancement factors for Rhodamine 6G were as high a s x 10⁷ --Abstract, page iv