EPITAXIAL-GROWTH OF 2,5-DISTYRYLPYRAZINE FROM THE VAPOR-PHASE

2,5-Distyrylpyrazine (DSP) was evaporated onto a cleavage face of KCl crystal in vacuo. The DSP film vacuum-evaporated on the KCl substrate without heat treatment was composed of randomly-oriented laminate and needle-like crystallites of alpha-form. When the substrate was heated at 150-degrees-C before vacuum evaporation and kept at 30-degrees-C during deposition, the DSP film was composed of slender needle-like crystallites of gamma-form and flaky crystallites of alpha-form. The longitudinal direction of the gamma-form crystals was aligned along the [100] and [010] directions of the KCl substrate. The faces of the alpha-form crystals made an angle of 10-degrees with respect to the [100] and [010] directions of the KCl substrate. At the substrate temperature of 70-degrees-C, the DSP film grew epitaxially on the substrate to form thin plate-shaped crystals of gamma-form. The DSP molecule took three kinds of orientations on the KCl substrate depending on the evaporation conditions: (100)-alpha-form parallel-to (001)KCl, (010)-alpha-form parallel-to (001)KCl and [100]-gamma-form perpendicular-to (001)KCl. These orientations are discussed in terms of the dehydroxylation of the KCl surface caused by the thermal treatment and of the adsorption energy of the DSP molecules.