Twofold Orientation of Triphenylene-Based Discotic Liquid Crystals on Gold
Résumé
Self-organization of first adsorbed monolayer of discotic liquid crystal, 2,3,6,7,10,11-hexapentyloxytriphenylene on the Au(111) surface was investigated by scanning tunneling microscopy at a solid/liquid interface. Visualizing the structure of the interface between organic molecules and the surface of the electrode is crucial for understanding the physics of potential devices, like organic light-emitting diodes or organic photovoltaic cells. We present images recorded with molecular resolution that reveal presence of ordered domains of hexagonal symmetry. Mutual distances between the centers of H5T lattice, combined with the orientation of the unit-cell suggest commensurability with the underneath metal surface. Two types of H5T lattices have been evidenced, coexisting on the same Au(111) substrate. They correspond to (7 x 7)R30 and (7 x 7)R44 structure of H5T molecules.