Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 14: Organic-inorganic hybrid systems and organic films II
O 14.4: Talk
Monday, March 12, 2018, 16:00–16:15, MA 042
Adsorption and Monolayer Formation of Sexiphenyl on In2O3(111) investigated with STM/AFM — •Margareta Wagner1, Jakob Hofinger1, Martin Setvín1, Lynn A. Boatner2, Michael Schmid1, and Ulrike Diebold1 — 1TU Wien, Austria — 2Oak Ridge National Laboratory, USA
The performance of an organic-semiconductor device is critically determined by the geometric alignment, orientation, and order of the organic molecules. While an organic multilayer eventually adopts the crystal structure of the organic material, the interface with the substrate/electrode material is often less well-defined. This work focuses on the prototypical organic molecule para-sexiphenyl (6P) and the thermodynamically most stable surface of the most-common transparent conducting oxide, indium (tin) oxide, In2O3(111). The onset of nucleation and the formation of the first monolayer are followed with scanning tunneling microscopy (STM) and constant-height non-contact atomic force microscopy (nc-AFM). At room temperature, 6P adsorbs lying on the surface and randomly oriented, i.e., without an ordered structure. Annealing to 200 ∘C provides sufficient thermal energy for the molecules to orient themselves along the high-symmetry directions of the surface, leading to a single adsorption site. With increasing coverage, the 6P molecules first form a lose network with poor long-range order but eventually the molecules re-orient and the first monolayer is established. It is a densely-packed, well-ordered (1×2) structure with one 6P per In2O3(111) substrate unit cell.