Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 97: Nanostructure at Surfaces: Structures and Properties
O 97.8: Vortrag
Freitag, 20. März 2015, 12:15–12:30, MA 005
A suitable tip for TERS? Find it out with photo-induced force microscopy (PiFM). — •Michael Ludemann1, Anne-D. Müller1, Falk Müller1, Derek Nowak2, and Sung I. Park2 — 1Anfatec Instruments AG, Melanchthonstr. 28, D-08606 Oelsnitz (V) — 2Molecular Vista Inc., 6840 Via Del Oro, CA-95199 San Jose (USA)
Tip-enhanced Raman spectroscopy (TERS) pushes down the spatial resolution of the measurement below the tip diameter and thus way beyond the diffraction limit of focused light.
Obtaining reproducible TERS results is difficult even with a proper setup. One key factor is a suitable tip.
PiFM offers the opportunity to characterize the tip at any time of the experiment. Here, the intensity of a linear polarized laser beam is modulated at a frequency in the range of the cantilever resonance. Illuminating the tip with the focused light induces a detectable dipole-dipole force even on non-metallic samples (e.g. glass). If the tip provides an appropriate near-field enhancement, a double lobe structure associated with the axial focal field created by a high-NA inverted objective lens is obtained while scanning the tip in the fixed laser focus. This way, PiFM can be utilized as a tool to validate the optical properties of the tip and the laser alignment.
The talk explains the physical background of PiFM and presents experimental results on differently prepared TERS tips.