Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 42: Plasmonics and Nanooptics III: Infrared Microscopy

O 42.4: Talk

Tuesday, March 8, 2016, 14:45–15:00, H4

Exploring local-scale phase transitions by low-temperature scattering scanning near-field optical microscopy — •Jonathan Döring, Susanne C. Kehr, and Lukas M. Eng — IAPP, Technische Universität Dresden

Using a low-temperature (T ≥ 4 K) scattering scanning near-field optical microscope (LT-s-SNOM) in conjunction with infrared photon excitation from a tunable free-electron laser (FEL) source, we are able to explore phase transitions in various systems down to the 1-nm length scale.

In LT-s-SNOM, the light scattered off an atomic force microscopy tip is strongly dependent on the tip-sample near-field interaction. Hence, recording this local light scattering enables imaging of optical properties with a resolution several orders of magnitude below the diffraction limit. The FEL laser light source provides high power densities and is precisely spectrally tunable from 4 to 250 µm. The unique combination of LT-s-SNOM and FEL thus allows for investigating a manifold of phonon-resonant phase transitions between 4 - 300 K by both nano-imaging and nano-spectroscopy. We report here on such studies for different systems; ferroelectric barium titanate [1] and doped lanthanum manganites [2]. Our LT near-field studies are backed-up by complementary piezo-response force microscopy (PFM) and Kelvin probe force microscopy (KPFM) performed in-situ with one and the same AFM.

[1] J. Döring et al., Appl. Phys. Lett. 105, 053109 (2014).

[2] E. Beyreuther et al., Phys. Rev. B 80, 075106 (2009).