[21p-P17-1~18] 12.2 Characterization and Materials Physics

[21p-P17-17] Surface T_g of organic amorphous films evaluated by nano-Marangoni effect

〇(B)Keishi Yamabayashi¹, Kazuma Kotani¹, Tsuyoshi Tsujioka¹ (1.Osaka Kyoiku Univ.)

Keywords:surface glass transition temperature, Marangoni effect, diarylethene

In this study, we propose a novel method to investigate the surface T_g region based on the nano-Marangoni effect. The nano-Marangoni effect is a flow phenomenon due to a fluctuation of local surface tension. Vacuum deposition of hetero-molecules on the organic surface generates islands of hetero-molecules by surface migration and aggregation. The mixed region in the interface between the island and the surface is generated by molecular diffusion and generates local fluctuation in surface tension. If surface has fluidity, the difference of surface tension forms the holes on the surface. When rubrene was deposited on the colored diarylethene (DAE) surface with a mean thickness of 2 nm, nano-scale holes on the DAE surface were observed. Depth of holes reflects the region with fluidity. As a result, the outermost surface T_g was estimated at -6℃ and was found to 100K-lower than bulk T_g (=94℃).