Controlling surface-enhanced Raman scattering (SERS) hotspot toward a narrow distribution of SERS enhancement factor (EF) is of paramount interest for linear response of SERS signal to the analyte concentration. In this talk, a single-nanogap level near-field characterization of ultra-dense nanogap-enhanced Raman scattering (NERS) array surface will be presented. Nanogaps were heavily populated between globular Ag nanoparticles (~120 particles/μm2) using a nanolithography-free simple process consisting of an Ar plasma treatment on polyethylene terephthalate (PET) wafer and successive Ag sputter deposition. Such compact nanogaps led to an exceptionally narrow SERS enhancement factor (EF) distribution (EFmax/EFmin&lt;101) measured from 3.1 × 105 confocal spots (0.1 μm2), which is one order of magnitude smaller than the detection areas (&gt; a few μm2) used in the vast majority of studies. The local near-fields at these nanogaps were visualized using photo-induced force microscopy (PiFM) that directly detected the near-field force under ambient conditions. An unprecedented spatial resolution (3.1 nm) was attained and the resulting photo-induced near-field force signals were quantitatively measured at each nanogap.

Single-nanogap level characterization of ultra-dense Nanogap-Enhanced Raman Scattering (NERS) array surface

253rd National Meeting (2017)

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