Dresden 2017 – wissenschaftliches Programm
DS 29.6: Vortrag
Mittwoch, 22. März 2017, 10:45–11:00, CHE 91
The growth of α-6T on different silver surfaces — •Thorsten Wagner, Ebrahim Ghanbari, Andrea Navarro-Quezada, and Peter Zeppenfeld — Johannes Kepler University, Linz, Austria
The combination of photoelectron emission microscopy (PEEM) and differential (optical) reflectance spectroscopy (DRS) is used to compare the growth of the prototype organic semiconductor α-sexithiophene (α-6T) on different silver surfaces, namely the Ag(111), the Ag(110), and the vicinal Ag(441) surface.
An unpolarized Hg lamp was used as excitation source for the photoelectrons. For all three substrates, the transient of the mean intensity obtained with PEEM follows the same trend: The first layer decreases the emission barrier for the photoelectrons and, hence, increases the electron yield. The deposition of additional molecules just decreases the electron yield, because the electron exclusively excited from the silver substrate have to pass through the molecular layers which do not further alter the emission barrier. In all three cases, at least an equivalent of two monolayers has to be deposited before nucleation of 3D crystallites is observed in PEEM.
After being reflected at the sample surface, the light of a white LED was split by a prism into its two linearly polarized components (pol-DRS). For the isotropic Ag(111) surface, the spectra obtained for s and p polarized light do not differ qualitatively. For the Ag(110) surface, the optical spectra indicate an orientation of the α-6T molecules along the  direction. On the Ag(441) surface, the molecules align parallel to the steps, i.e., along the  direction.