Super-Resonant Infrared Near-Field Microscopy


Super-Resonant Infrared Near-Field Microscopy

Lang, D.; Uhlig, T.; Kehr, S. C.; Eng, L. M.; Helm, M.

Scattering-type scanning near-field optical microscopy (s-SNOM) is an AFM-based technique for achieving nanoscale resolution even at infrared wavelengths [1]. s-SNOM thus is of valuable impact when investigating low-dimensional conductors or semiconductors. Nevertheless, the scattered near-field signal strongly depends on the dielectric function of both tip and sample. In order to enhance this signal strength we face two options, by either tuning the tip or sample into resonance using appropriate or tunable laser light sources, and resonant tip materials.


In this work we use a CO2-laser with a tunable center wavelength from 9.7 µm to 11.3 µm as an infrared excitation source in combination with self-prepared AFM particle-tips as probes [2]. The tip particles consist of spherical silicon carbide (SiC), silicon nitride (Si3N4) or silicon oxide (SiO2) nanoparticles with a diameter of ~ 60 nm. Those materials show phonon resonances in or around the CO2-laser wavelength range and thus enhance the signal significantly. We explored here the scenario when using both resonant tips AND samples, hence resulting in a tip-sample coupled super-resonance where both the tip and the sample contribute to the signal-enhancement. Accordingly, a significantly increased near-field image contrast and resolution is expected in this case.

References:


[1] S.C. Kehr et al., Nat. Commun. 2, 249 (2011).

[2] M.T. Wenzel et al., Optics Express 16 (16), 12302-12312 (2008).

Keywords: CO2-laser; near-field infrared microscopy; phonon resonance

  • Poster
    79. DPG-Jahrestagung und DPG-Frühjahrstagung, 15.-20.03.2015, Berlin, Deutschland
  • Poster
    German THz Conference 2015, 08.-10.06.2015, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22941
Publ.-Id: 22941