A Closer Look at Corrugated Au Tips

Journal Article · Thu Mar 05 04:00:00 EST 2020 · The Journal of Physical Chemistry Letters

DOI:https://doi.org/10.1021/acs.jpclett.0c00305· OSTI ID:1605415

Bhattarai, Ashish ^[1]; Crampton, Kevin T. ^[1]; Joly, Alan G. ^[1]; Wang, Chih-Feng ^[1]; Schultz, Zachary ^[2]; El-Khoury, Patrick Z. ^[1]

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1. BATTELLE (PACIFIC NW LAB)
2. Ohio State University

A series of optical and electron microscopies are utilized in concert to unravel the structural, optical, and plasmonic properties of corrugated metallic tips. While the overall microscopic shapes of the tips dictate their optical resonances and plasmonic field enhancement factors, nanometric structural details govern their tip-enhanced Raman (TER) spectra and images. Using 4-thiobenzonitrile (TBN) as a molecular reporter, spatially resolved TER spectra reveal that optical rectification and molecular charging are among the prominent observables in the tip-tip TER geometry. The comparisons we provide reinforce the complexity of what otherwise may be regarded as sharp tip probes. We show the spurious appearance of anions is driven by highly localized resonances that appear as a result of surface corrugation and their manifestation throughout the course of TER nano-spectroscopy complicates spectral assignments, particularly in works aimed at understanding plasmon-enhanced/induced chemical transformations through enhanced Raman spectroscopy and imaging. Overall, nanoscale spatial variations in the TERS spectra suggest that the tip-tip geometry sustains junction plasmons that appear very different from what may be expected from the hybridization of the bulk tip resonances.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1605415
• Report Number(s): PNNL-SA-150954
• Journal Information: The Journal of Physical Chemistry Letters, Journal Name: The Journal of Physical Chemistry Letters Journal Issue: 5 Vol. 11
• Country of Publication: United States
• Language: English