Nanoscale infrared absorption spectroscopy of individual nanoparticles enabled by scattering-type near-field microscopy.
ACS Nano
; 5(8): 6494-9, 2011 Aug 23.
Article
en En
| MEDLINE
| ID: mdl-21770439
ABSTRACT
Infrared absorption spectroscopy is a powerful and widely used tool for analyzing the chemical composition and structure of materials. Because of the diffraction limit, however, it cannot be applied for studying individual nanostructures. Here we demonstrate that the phase contrast in substrate-enhanced scattering-type scanning near-field optical microscopy (s-SNOM) provides a map of the infrared absorption spectrum of individual nanoparticles with nanometer-scale spatial resolution. We succeeded in the chemical identification of silicon nitride nanoislands with heights well below 10 nm, by infrared near-field fingerprint spectroscopy of the Si-N stretching bond. Employing a novel theoretical model, we show that the near-field phase spectra of small particles correlate well with their far-field absorption spectra. On the other hand, the spectral near-field contrast does not scale with the volume of the particles. We find a nearly linear scaling law, which we can attribute to the near-field coupling between the near-field probe and the substrate. Our results provide fundamental insights into the spectral near-field contrast of nanoparticles and clearly demonstrate the capability of s-SNOM for nanoscale chemical mapping based on local infrared absorption.
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Dispersión de Radiación
/
Espectrofotometría Infrarroja
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Nanotecnología
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Nanopartículas
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Microscopía
Idioma:
En
Revista:
ACS Nano
Año:
2011
Tipo del documento:
Article
País de afiliación:
España