EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) is a scanning probe approach to optical microscopy and spectroscopy bypassing the ubiquitous diffraction limit of light to achieve a spatial resolution. s-SNOM employs the strong confinement of light at the apex of a sharp metallic AFM tip to create a nanoscale optical hot-spot. Analyzing the scattered light from the tip enables the extraction of the optical properties (dielectric function) of the sample and yields nanoscale resolved images simultaneous to topography [1]. In addition, the technology has been advanced to enable Fourier-Transform Infrared Spectroscopy on the nanoscale (nano-FTIR) [2] using broadband radiation from the visible spectral range to THz frequencies.

Recently, the combined analysis of complex nanoscale material systems by correlating near-field optical data with information obtained by other SPM-based measurement methodologies has gained significant interest. For example, the material-characteristic nano-FTIR spectroscopic imaging of a phase-separated PS/LDPE polymer blend verifies sharp material interfaces. Complementary near-field imaging at 1500cm-1 verifies the change of the materials on a length scale <25nm. Correlative mapping of nano-mechanical properties like adhesion of the different materials [3,4] fully analyses the ca. 50nm thin film.

Other applications include correlation of nanoscale electrical properties of functional nanostructures by KFPM with near-field microscopy in the THz frequency range. With the ability to determine the charge carrier concentration in a contact-free manner from s-SNOM images[5], the correlative measurements to the local work function can be used for a comprehensive characterization of the functional semiconductor nanostructures.

1. F. Keilmann, R. Hillenbrand, Phil. Trans. R. Soc. Lond. A 362, 787 (2004).
2. F. Huth, et al., Nano Lett. 12, 3973 (2012).
3. B. Pollard, et al., Beilstein J. of Nanotechn. 7, 605 (2016).
4. I. Amenabar, et al., Nature Commun. 8, 14402 (2017).
5. C. Liewald, et al., Optica 5, 159, 2018