Nano-FTIR Absorption Spectroscopy
of Molecular Fingerprints
at 20 nm Spatial Resolution
- Publication date
- Publisher
Abstract
We demonstrate Fourier transform infrared nanospectroscopy
(nano-FTIR)
based on a scattering-type scanning near-field optical microscope
(s-SNOM) equipped with a coherent-continuum infrared light source.
We show that the method can straightforwardly determine the infrared
absorption spectrum of organic samples with a spatial resolution of
20 nm, corresponding to a probed volume as small as 10 zeptoliter
(10<sup>–20</sup> L). Corroborated by theory, the nano-FTIR
absorption spectra correlate well with conventional FTIR absorption
spectra, as experimentally demonstrated with poly(methyl methacrylate)
(PMMA) samples. Nano-FTIR can thus make use of standard infrared databases
of molecular vibrations to identify organic materials in ultrasmall
quantities and at ultrahigh spatial resolution. As an application
example we demonstrate the identification of a nanoscale PDMS contamination
on a PMMA sample