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Scattering Type Scanning Near-field Optical Microscopy and Nano-FTIR Spectroscopy


Scattering type scanning-near-field optical microscopy (s-SNOM) is a fast, non-destructive and surface sensitive optical technique. S-SNOM is based on atomic force microscopy (AFM), where a focused laser beam is additionally utilized to illuminate the tip. The metallic probe acts as an antenna which confines the incident electric field around the tip-apex thus providing a nanoscale light source for label-free high-resolution imaging. This enables the simultaneous acquisition of detailed topographic and optical information on the local sample properties with a spatial resolution below 50 nm. The use of continuous and broadband synchrotron radiation provided by the Metrology Light Source (MLS) permits also to perform nano-FTIR spectroscopy which enables spectroscopic characterization of thin surface layers and nanosystems [1, 2].


In general, sample suitable for imaging in non-contact mode may be investigated

  • Imaging and determination of surface roughness by AFM
  • Near-field imaging at discrete wavelengths with tunable gas lasers
  • Broadband nano-FTIR spectroscopy

Technical Specifications

  • NeaSNOM scattering type near-field microscope (Neaspec GmbH, Germany) and AFM
  • Radiation sources:

    • CO and CO2 lasers for the wavelength ranges from 5,2 µm to 6,1 µm and 9,4 µm to 10,8 µm
    • continuous and broadband synchrotron radiation from IR-beamline of the electron storage ring (MLS)

  • Detectors for different wavelength ranges:

    • MCT-detector for 2 µm to 12 µm
    • InSb-detector for 1 µm to 5 µm

  • Commercial Au or Pt/Ir coated Si-based near-field probes

Research Topics

Using the s-SNOM methodology the group performs fundamental and environmental metrology research and aims at supporting the development of key technologies, in particular energy-, bio- and nanotechnology, as well as microelectronics. Ongoing specific research topics are:

  • Characterization of intrinsic strain in semiconductor and piezoelectric nanostructures (EMRP Nanostrain)
  • Near-field imaging and spectroscopy of biological nanostructures (EMRP Q-AIMDS)
  • Novel microelectronic materials (Graphene, MoS2) (collaboration with FU Berlin)
  • Characterization of materials used in environmental research (collaboration with BAM)
  • Contactless thermography [3]
  • Adaption of synchrotron radiation for broadband SNOM/nano-FTIR (collaboration with HZB)
Fig. 1: IR-SNOM image of 16 nm high SiO2 patterns on Si substrate demonstrating the resolving power of the optical near-field [2].