[11p-M112-1~15] 12.2 Characterization and Materials Physics

▲ [11p-M112-2] Study of local structure in rubrene thin films by Scanning Transmission X-ray Microscopy

〇(D)Alexandre Foggiatto¹, Yasuo Takeichi², Kanta Ono², Hiroki Suga³, Yoshio Takahashi³, Michael A. Fusella⁴, Jordan T. Dull⁴, Barry P. Rand⁴, Kentaro Kutsukake⁵, Takeaki Sakurai¹ (1.Univ. Tsukuba, 2.KEK IMSS, 3.Univ.Tokyo, 4.Princeton Univ., 5.RIKEN)

Keywords:organic semiconductor, scanning transmission X-ray microscopy, rubrene

In this work, we used scanning transmission X-ray microscope (STXM) combined with image analysis processing to investigate the orthorhombic (also referred as “platelet”) and spherulite rubrene thin films. We observed that the platelet film has more oriented molecules on the crystal than the spherulite one. On the grain boundary of the spherulite film, by the line profile, we can notice that on the grain boundary, due to the preparation temperature and the weakly Van der Walls attraction between the molecules in the film, there is a high number of misoriented molecules which can act as barrier to the charge flows resulting on the dropped of mobility on this film compared to the smooth boundary in the platelet film.The roughness of the boundary, obtained by the root mean square (RMS) for the center of the boundary line compared to a straight line, is calculated as 0.04 and 0.14 μm for the platelet and spherulite, respectively, which corroborates our assumption. The same feature is also observed on the boundary of the fibrous structure of the spherulite thin film.