Self-Assembled Growth of Highly Oriented Para-Sexiphenyl Thin Films Controlled by Elastic Strain

摘要

We have studied the structure and growth regularities of highly ordered para-sexiphenyl (C_(36)H_(26)) thin films deposited by Hot Wall Epitaxy on mica. In particular, atomic force microscopy (AFM) was used to investigate the early growth stage of these films, in order to find the process controlling parameters. It was shown that the substrate temperature and the growth time are important parameters for control of the film morphology, in terms of the degree of anisotropy and long range order. X-ray diffraction pole figure technique and transmission electron microscopy were also used to characterize the crystallographic structure of the thicker films. We have shown that the highly ordered crystallites of para-sexiphenyl (showing needle-like morphology by AFM) are oriented with their (11(1-bar)) or (11(2-bar)) crystallographic planes parallel to the substrate surface. For each of these two orientations there are two opposite directions for growth of crystallites reflecting the two-fold symmetry of the mica surface.