Berlin 2008 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 38: Vibrational Spectroscopy of Nanolayers with Optical Probes
DS 38.2: Hauptvortrag
Freitag, 29. Februar 2008, 15:45–16:15, H 2013
UHV-based TERS on adsorbed molecules — •Bruno Pettinger and Jens Steidtner — Fritz-Haber-Institut der MPG, Faradayweg 4-6, D-14195 Berlin
In recent years tip-enhanced Raman spectroscopy (TERS) has proven to be a feasible tool for the local investigation of surfaces on a nanometer scale, in some cases with single molecule sensitivity [1]. So far, TERS experiments were performed in the gas phase and under atmospheric pressure, which entails some disadvantages as e.g. the possible contamination of the tip and the sample. Here we present a novel microscope based on a high-numerical parabolic mirror for focusing the laser to a minimum size spot and collecting the scattered light. The SPM and the essential optical components are combined on a rigid platform, which is mounted in an UHV system. Optical fibers connect this setup with remote laser and spectrograph. The focusing of the laser onto the tip apex and maximizing the scattered intensity is achieved by a five-axis alignment of the parabolic mirror by piezo-motors. For dye adsorbates on smooth Au(111) samples, the approach of a STM tip boosts the Raman scattering signal from a small region with a diameter of only a few nanometers to a 4000-fold level, which means an underlying enhancement of TERS of 106 - 107. This huge enhancement causes in UHV only a minor photodecomposition, much in contrast to comparable experiments in air, and thus allows to move toward single molecule spectroscopy and microscopy. Preliminary results on this topic will be presented.
1. K.F. Domke et al., J. Am. Chem. Soc. 128, 14721 (2006).