SERS hot spots

Abstract

Hot spots are highly localized regions of intense local field enhancement believed to be caused by local surface plasmon resonances (LSPR). Formed within the interstitial crevices present in metallic nanostructures [1-4], such hot spots have been claimed to provide extraordinary enhancements of up to 1015 orders of magnitude to the surface-enhanced Raman scattering (SERS) signal (proportional to |E| 4 ) [5] in areas of subwavelength localization [6, 7]. As a result, hot spots are critically important for SERS and, if in sufficient density, can dominate the properties of any SERS active substrate within which they reside. Given their characteristics, hot spots are now widely acknowledged to be a prerequisite for the observation of single-molecule SERS and set the limit for the achievable spatial resolution for SERS as applied to scanning probe microscopy with high chemical specificity also known as tip-enhanced Raman spectroscopy (TERS). As a result of their importance to SERS, hot spots have generated a great deal of interest in the last 5 years. This review summarizes the key results from recent theoretical and experimental investigations focused on improving the understanding of the characteristics of SERS hot spots and their control.