Near-field infrared microscopy on carbon nanostructures
Prof. Katalin Kamaras
Research Professor
Institute for Solid State Physics and Optics
Wigner Research Centre for Physics
Scattering near-field optical microscopy (s-SNOM), based on the combination of atomic force microscopy and frequency-dependent light scattering, is an emerging method that combines high spatial resolution with high sensitivity even at long illuminating wavelengths. I will present results in the infrared frequency range obtained on various carbon nanostructures. The most obvious task, identifying individual molecules, is also the most difficult, due to the weak scattering from molecular vibrations. Free (Drude) electrons in metallic carbon nanotubes or encapsulated metal clusters are more easily detected. The intense field under the tip can also be used to launch and detect the charge distribution inside nanotubes caused by interference of quasiparticles: plasmon-polaritons or phonon-polaritons. The interaction of phonon-polaritons with vibrational modes of molecules confined in the tubes brings the capabilities of the method full circle, enabling to reach a detection threshold of a few hundred molecules and follow their chemical reactions by infrared spectroscopy.