Since the first demonstration of scanning near-field optical microscopy more than twenty years ago the main motivation has always been to detect and identify chemical structures by spectroscopic means with the high spatial resolution of scanning-tip microscopy. Many interesting samples are non-transparent and hence it is difficult if not impossible to access optically the nanometer gap between the probing tip and the surface with high spatial resolution. Quantitative spectroscopic measurements with an optical resolution matching the size of molecules is hence difficult and has been plagued either by a lack of resolution, contrast or sensitivity. To address this challenging task we have developed a near-field optical microscope with a parabolic mirror for tip illumination and signal collection that are performed from the top of the sample under perfect diffraction and polarization conditions. No restrictions apply with respect to the conductivity or transparency of the samples. We will provide illustrative examples from material science to demonstrate the performance with respect to spectroscopic imaging (tip-enhanced photoluminescence, TEPL and tip-enhanced Raman scattering, TERS), sensitivity and resolution such as molecular (mono-) layers, quantum dots, organic semiconductor films and single surface states on TiO2 single crystals.


Wednesday, October 30, 2013, 15:00. Seminar Room

Hosted by Prof. Niek van Hulst