s-SNOM (scattering-type Scanning Near-field Optical Microscopy) delivers material-characteristic maps of chemical and optical properties of sample surface at the spatial resolution of an atomic force microscope (AFM). Tuning the illumination wavelength, i.e. „color“ of the light source used for measurements provides spectroscopic information at the nanoscale.

Basic probing principle:

  1. focus laser light onto a sharp AFM tip;
  2. illuminated tip creates a strong near-field nano-focus at its apex;
  3. nano-focus probes optical properties of the sample below the tip, modifying the tip-scattered light;
  4. all-optical interferometric detection recovers both amplitude and phase of the tip-scattered light, delivering complete information about the sample’s complex optical properties (e.g. absorption and reflectivity).

s-SNOM provides nanoscale mapping of chemical and optical properties

Challenge: Small size of the nano-focus demands for a state-of-the-art detection to extract weak near-field signal from the dominant background.

neaspec developed and patented all detection technologies that provide guaranteed 100% background suppression for reliable and reproducible near-field imaging and spectroscopy across THz, mid-IR, near-IR and Visible spectral ranges.

s-SNOM is based in on an asymmetric interferometer where the AFM tip and the sample are located in one of the interferometer arms. The light from the tip-sample arm is recombined with the reference beam at the detector. Patented interferometric detection based on varying the reference mirror position, thus reference phase, allows for simultaneous recording of phase and amplitude of the tip-scattered light, which relate to the local reflectivity and absorption. Modulating the reference phase also enables complete suppression of scattering background. This way, s-SNOM returns pure optical/chemical near-field maps free of mechanical artifacts – all simultaneously with AFM topography and phase.

List of s-SNOM detection technologies invented and patented by neaspec all providing 100% background suppression:
  • PsHet (Pseudo-Heterodyne): golden standard for nanoscale imaging.
  • P-Spec: PsHet-quality s-SNOM point spectroscopy by laser sweeping.
  • HSH (High-Speed Holography): fastest imaging method for screening of large sample areas with the best S/N quality of all known s-SNOM imaging methods.
  • nano-FTIR: the only method for nanoscale spectroscopy and hyperspectral imaging with broadband illumination sources.

Compare different s-SNOM technologies and learn why neaspec is the market leader.

 

neaspec s-SNOM technology provides:

  • Highest versatility with proven performance on all material classes

proven performance on all material classes

  • 100% background suppression for reproducible artifact-free imaging and spectroscopy

100% artifact-free

  • Best-in-class sensitivity capable of detecting single monolayers and individual macromolecules

single molecule sensitivity

  • Nanoscale imaging & point spectroscopy for rapid component mapping and chemical identification

point spectroscopy with highest resolution

  • Simultaneous absorption & reflectivity at each pixel for complete characterization of sample’s optical properties with 10 nm spatial resolution

absorption + reflectivity at each ixel

  • Electric field amplitude and phase mapping at 10 nm spatial resolution for complete modal analysis: attenuation, mode profile, wavelength, dispersion

filed mapping: amplitude and phase

  • Access to the dielectric function at the nanoscale, i.e. refractive index and attenuation coefficient

  • Quantitative subsurface analysis for complete chemometric analysis and characterization of sample structure

subsurface detection

  • Nanoscale sample analysis at THz, IR and visible spectral ranges
    vis to THz carrier profiling
  • Exclusive s-SNOM point spectroscopy of low energy vibrations down to ca. 545 cm-1 for nanoscale analysis crystalline materials.
    Point spectra of Forsterite, Titanate and Microcline

s-SNOM Advantages & Strengths

Purely Optical

Direct optical measurements unaffected by tip or sample mechanics

max performance

Highest Sensitivity

Best-in-class sensitivity from monolayer to single macromolecules

Proven Technology

Trusted

Proven, well-understood and trusted technology

Subsurface analysis

Subsurface

Capable of spectroscopic surface and subsurface analysis

Analytical

Provides access to refractive index and absorption coefficient for ultimate chemometric analysis

Highest Versatility

Works for all materials – absorbing or not – and in all spectral ranges (from visible to sub-THz)

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