The present invention relates generally to methods for fabricating substrates suitable for use in analytical and diagnostic optical systems, and in particular, substrates for use in Raman spectroscopy.
Raman spectroscopy can be employed as an analytical as well as a diagnostic technique in a variety of applications, such as material characterization and identification. It relies on inelastic scattering of incident photons by a molecule, via coupling to its vibrational modes, to provide an essentially unique signature for that molecule. In particular, such inelastic scattering (commonly known as Raman scattering) can cause a decrease or an increase in the scattered photon energy, which appear as “Stokes” and “anti-Stokes” peaks in a wavelength-dispersed spectrum of the scattered photons. A drawback of Raman spectroscopy is the relatively few incidences of such inelastic scattering. The probability that a scattering event will occur is typically called “cross-section,” which is expressed in terms of area.
Raman scattering cross-sections can, however, be significantly enhanced by placing the molecule on or near a conductive surface. Such a mode of performing Raman spectroscopy is commonly known as surface enhanced Raman spectroscopy (SERS). Although SERS is a promising technique for extending the use of Raman spectroscopy to a variety of new applications, its use is currently limited due to a dearth of reliable, high performance substrates.
Accordingly, there is a need for substrates for use in SERS, as well as other applications, that can provide a high degree of reliability and performance. There is also a need for methods of fabricating such substrates with a high degree of reproducibility, which can be easily and, preferably inexpensively, implemented.