Multimodal Tip Enhanced Raman Microscopy with a Cylindrical Vector Beam Focused by a Parabolic Mirror

Abstract

This work describes the development and the implementation of several new functions in an existing near-field optical microscope based on a parabolic mirror for excellent tip illumination and optical signal collection. The improved microscope is an ideal tool for performing imaging and spectroscopy on opaque samples, in particular molecular films deposited on flat substrates with a spatial resolution on the order of several nm. The new functions were hyperspectroscopic imaging, fluorescence life time imaging (FLIM) and scanning bias voltage tip enhanced Raman spectroscopy (SBV-TERS) based on a self built Scanning Tunneling Microscope (STM)-scan head. Utilizing these improvements, several new measurement methods have been developed, were the bias voltage is used to apply a strong electric field in the gap mode to manipulate and directly monitor the sample on a molecular scale. The results out of this thesis demonstrate how optical enhancement inside the gap mode can be further increased by a stronger localization via tunneling through a molecule. The bias voltage activated stimulated emission from an illuminated single molecule tunneling junction can improve the fundamental understanding of quantum plasmonics and lead to new analytical applications. Furthermore, this concept represents the basis for novel ultra-small, fast, optically and electronically switchable devices and could find applications in high-speed signal processing and optical telecommunications. The thesis is composed on the development of the setup and the following experiments exploring different questions on organic semi conductors. This work consists three chapters, describing the evolution of the microscope and the methods used for investigating different molecular systems which are relevant for organic electronics.