Optical spectroscopy of large organic molecules on insulating surfaces: Approaching the single molecular limit for PTCDA on KCl(100) step sites

Date

Sep 6, 2017

Time

4:30 PM - 5:30 PM

Speaker

Christian Marquardt

Affiliation

Universität Bonn

Language

en

Main Topic

Physik

Other Topics

Physik

Description

The investigation of the optical properties of organic molecules adsorbed on surfaces is inter- esting both from a fundamental and a technological point of view. Due to the specific interac- tions with the surface these properties are strongly affected, which can for example be used to identify different adsorption sites or investigate the mechanisms that are responsible for these optical changes. The model system PTCDA/KCl(100) is exceptionally well suited for studying such effects, since the specific binding of the functional groups of the PTCDA molecules to the ions of the KCl surface results in highly defined adsorption sites with little site disorder. This considera- bly reduces the inhomogeneous broadening and allows to measure fluorescence and fluores- cence excitation spectra with high resolution and detail. Nevertheless, these spectra are still inhomogeneously broadened and resemble an averaged ensemble. The next step is therefore to overcome the inhomogeneous broadening by spatial and spectral dilution and measure ho- mogeneously broadened single molecule spectra with maximum resolution and highest sensi- tivity for environmental changes. In this talk I will start with an introduction into fluorescence spectroscopy on organic mole- cules adsorbed on surfaces and give an overview on results concerning a diluted phase of PTCDA molecules on KCl(100). Here, the focus will be on different adsorption sites and how their specific environment influences the optical spectra. In the second part I will present the first results on the single molecule level. Here we were able to measure the homogeneous linewidth for molecules at KCl step-edge sites and observe photophysical processes like a saturation behavior and spectral jumps.

Last modified: Sep 6, 2017, 10:03:17 AM