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O: Oberflächenphysik
O 35: Organic films III
O 35.5: Vortrag
Donnerstag, 30. März 2006, 12:15–12:30, WIL B321
Optical Evidence for Substrate Induced Growth of Ultra-thin Hexa-peri-hexabenzocoronene Layers on HOPG — •Roman Forker1, Thomas Dienel1, Klaus Müllen2, and Torsten Fritz1 — 1Institut für Angewandte Photophysik, TU Dresden, Germany — 2MPI für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
We report on the influence of the substrate on the optical properties of ultra-thin hexa-peri-hexabenzocoronene (HBC) layers deposited by organic molecular beam epitaxy (OMBE). For that purpose, the in situ differential reflectance spectroscopy (DRS) was employed, providing unsurpassed sensitivity for the thickness-dependent optical analysis. From the DR spectra, the optical constants were extracted using a novel numerical algorithm [1]. It turns out that HBC films on different substrates exhibit different growth modes which could be confirmed by structural examinations.
While HBC shows polycrystalline island structures on mica and on fused quartz, layer-by-layer growth along with the formation of one-dimensional stacks on HOPG could be demonstrated optically. The observed monomer → dimer → oligomer transition was related to the well-known findings for perylenetetracarboxylicdianhydride (PTCDA) layers on mica [2, 3].
[1] R. Nitsche et al., Phys. Rev. B 70 (2004), 195432
[2] H. Proehl et al., Phys. Rev. Lett. 93 (2004), 097403
[3] H. Proehl et al., Phys. Rev. B 71 (2005), 165207