Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 28: Organic-Inorganic Systems I: PTCDA

O 28.4: Talk

Tuesday, March 8, 2016, 11:30–11:45, S054

Structure and thermal stability of organic heterostructures on Ag(111) — •Sebastian Thussing, Laura Fernandez, and Peter Jakob — Fachbereich Physik, Philipps-Universität Marburg, Renthof 5, 35032 Marburg, Germany

The growth of highly ordered molecular films exceeding the first few monolayers represents a challenge as these layers are inherently unstable and susceptible to dewetting processes. Understanding the kinetics of associated phase transformations and proper characterization tools are therefore crucial in such studies. We have investigated the thermal stability and intermixing of various heterolayer model systems (stacked CuPc/PTCDA and TiOPc/PTCDA layers grown on Ag(111)) by means of analyzing the characteristic vibrational modes of these molecules using IR spectroscopy. In addition, SPA-LEED provided information regarding the lateral ordering of these layers. We find that the growth of TiOPc layers on Ag(111) leads to the formation of a stable bilayer where the first layer is oriented with "Ti=O up" and the second layer with "Ti=O down". This particular structural arrangement is attributed to a minimization of dipole-dipole interaction within this stacked Ti=O assembly. Considering the stability of this configuration, bilayers of TiOPc (and CuPc for comparison) have been combined with PTCDA contact primer layers. Again the TiOPc-bilayer exhibits exceptional thermal stability with minimal intermixing with underlying PTCDA/Ag(111) up to about 450K. This is in contrast to the growth of a CuPc bilayer on PTCDA/Ag(111) which shows negligible intermixing but CuPc cluster formation already at T = 250K.