Tip-enhanced near-field Raman spectroscopy with a scanning tunneling microscope and side-illumination optics

Conventional Raman spectroscopy (RS) suffers from low spatial resolution and low detection sensitivity due to the optical diffraction limit and small interaction cross sections. It has been reported that a highly localized and significantly enhanced electromagnetic field could be generated in the pr...

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Bibliographic Details
Published inReview of scientific instruments Vol. 79; no. 7; p. 073706
Main Authors Yi, K J, He, X N, Zhou, Y S, Xiong, W, Lu, Y F
Format Journal Article
LanguageEnglish
Published United States 01.07.2008
Subjects
Electromagnetic Fields
Equipment Design
Gold - chemistry
Lasers
Light
Metals
Microscopy, Electron, Scanning
Microscopy, Scanning Tunneling - instrumentation
Microscopy, Scanning Tunneling - methods
Nanoparticles - chemistry
Nanotechnology - instrumentation
Nanotechnology - methods
Optics and Photonics
Silicon - chemistry
Silver - chemistry
Spectrum Analysis, Raman - instrumentation
Spectrum Analysis, Raman - methods
Tungsten - chemistry
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Summary:Conventional Raman spectroscopy (RS) suffers from low spatial resolution and low detection sensitivity due to the optical diffraction limit and small interaction cross sections. It has been reported that a highly localized and significantly enhanced electromagnetic field could be generated in the proximity of a metallic tip illuminated by a laser beam. In this study, a tip-enhanced RS system was developed to both improve the resolution and enhance the detection sensitivity using the tip-enhanced near-field effects. This instrument, by combining RS with a scanning tunneling microscope and side-illumination optics, demonstrated significant enhancement on both optical sensitivity and spatial resolution using either silver (Ag)-coated tungsten (W) tips or gold (Au) tips. The sensitivity improvement was verified by observing the enhancement effects on silicon (Si) substrates. Lateral resolution was verified to be below 100 nm by mapping Ag nanostructures. By deploying the depolarization technique, an apparent enhancement of 175% on Si substrates was achieved. Furthermore, the developed instrument features fast and reliable optical alignment, versatile sample adaptability, and effective suppression of far-field signals.
ISSN:0034-6748
DOI:10.1063/1.2956977