2006 年 33 巻 4 号 p. 237-
The "vicinal steps" on a substrate surface are useful to control in-plane orientations of organic thin-film crystals at a "nucleation" stage. In addition to a "nucleation" process, we also focused attention on a "growth" process, on which vicinal steps should also give their effects. Hence, we grew Pentacene (Pn) thin film crystals on vicinal hydrogen-terminated Si(111) (H-Si(111)) surfaces, and studied the effects of vicinal steps of H-Si(111) on the growth of the Pn thin film crystals by observing the morphology of the thin film with atomic force microscopy. We found that the first layer of the Pn thin film crystals exhibited a significantly anisotropic shape on a vicinal H-Si(111) surface: dendritic branches evolved in a lower terrace side (Si direction) but compact shape appeared in an upper terrace side (Si direction), although the first layer showed an isotropic shape on a flat H-Si(111) surface. Furthermore, the growth of the first layer was much faster in the lower-terrace-side direction than in the upper-terrace-side direction. Since such anisotropic growth was observed irrespective of the directions of an incident Pn molecular beam, we tentatively concluded that the cause of the anisotropic growth would be the anisotropy in the incorporation kinetics of Pn molecules at the edges of the thin film crystals on a vicinal surface.