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Title: Tip-Enhanced Raman Nanographs: Mapping Topography and Local Electric Fields

We report tip-enhanced Raman scattering experiments in which topographic and local electric field images are recorded simultaneously. We employ a Raman-active 4,4’-dimercaptostilbene (DMS)-coated gold tip of an atomic force microscope to map the topography and image electric fields localized at nanometric (20 and 5 nm-wide) slits lithographically etched in silver. Bi-modal imaging is feasible by virtue of the recorded scanning probe position-dependent frequency-resolved optical response, which can be sub-divided into two components. The first is a 500-2250 cm-1 Raman-shifted signal, characteristic of DMS. The molecular response reports on topography through intensity contrast in the absence/presence of a plasmonic junction formed between the scanning probe and patterned silver surface. Here, we demonstrate that sub-15 nm spatial resolution is attainable using a 30 nm DMS-coated gold tip. The second response consists of two correlated sub-500 cm-1 signals arising from mirror-like reflections of (i) the incident laser, and (ii) the Raman scattered response of an underlying glass support (at 100-500 cm-1) off the gold tip. We show that both the low-wavenumber signals trace the local electric fields in the vicinity of the nanometric slits.
Authors:
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Publication Date:
OSTI Identifier:
1172173
Report Number(s):
PNNL-SA-106991
48129
Grant/Contract Number:
AC05-76RL01830
Type:
Published Article
Journal Name:
Nano Letters, 15(4):2385-2390
Additional Journal Information:
Journal Name: Nano Letters, 15(4):2385-2390
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Environmental Molecular Sciences Laboratory