Unique Orientation of Organic Epitaxial Thin Films: The Role of Intermolecular Interactions at the Interface and Surface Symmetry

The investigation of the mechanisms driving the growth of single crystalline organic thin films is a fundamental issue of organic electronics in view of the optimization of transport properties in thin film-based devices. In this paper, a complete azimuthal order of heteroepitaxial domains of alpha-quaterthio-phene grown by organic molecular beam epitaxy on tetracene single crystal substrates is assessed by oblique incidence absorption spectroscopy and fully validated by empirical force field calculations. The effect of the many-body interactions combined with the symmetry of the substrate and deposit surfaces involved in the heterojunction is demonstrated to drive toward this relevant achievement, which unveils new strategies for controlling the growth of single crystalline organic thin films.