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Three-Dimensional Molecular Packing of Thin Organic Films of PTCDI-C8 Determined by Surface X-ray Diffraction

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journal contribution
posted on 18.11.2008, 00:00 by Tobias N. Krauss, Esther Barrena, Xue N. Zhang, Dimas G. de Oteyza, János Major, Volker Dehm, Frank Würthner, Leide P. Cavalcanti, Helmut Dosch
We have determined the full molecular 3D packing of thin organic films of the archetypical organic n-type semiconductor N,N′-dioctyl-3,4:9,10-perylene tetracarboxylic diimide (PTCDI-C8) by surface X-ray crystallography. We show that PTCDI-C8 forms smooth layered films on Al2O3 (11−20) with an outstanding degree of molecular order. The thin-film structure is found to consist of a triclinic unit cell with the plane of the aromatic core tilted by 67 ± 2° with respect to the surface plane, which differs significantly from the bulk structure. The 3D crystallites extend with vertical coherent order across the entire film thickness.