Interface Induced Crystal Structures of Dioctyl-Terthiophene Thin Films

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• 作者：Oliver Werzer ; Nicolas Boucher ; Johann P. de Silva ; Gabin Gbabode ; Yves H. Geerts ; Oleg Konovalov ; Armin Moser ; Jiri Novak ; Roland Resel ; Michele Sferrazza
• 刊名：Langmuir
• 出版年：2012
• 出版时间：June 5, 2012
• 年：2012
• 卷：28
• 期：22
• 页码：8530-8536
• 全文大小：354K
• 年卷期：v.28,no.22(June 5, 2012)
• ISSN：1520-5827

文摘

Temperature dependent structural and morphological investigations on semiconducting dioctyl-terthiophene (DOTT) thin films prepared on silica surfaces reveals the coexistence of surface induce order and distinct crystalline/liquid crystalline bulk polymorphs. X-ray diffraction and scanning force microscopy measurements indicate that at room temperature two polymorphs are present: the surface induced phase grows directly on the silica interface and the bulk phase on top. At elevated temperatures the long-range order gradually decreases, and the crystal G (340 K), smectic F (348 K), and smectic C (360 K) phases are observed. Indexation of diffraction peaks reveals that an up-right standing conformation of DOTT molecules is present within all phases. A temperature stable interfacial layer close to the silica鈥揇OTT interface acts as template for the formation of the different phases. Rapid cooling of the DOTT sample from the smectic C phase to room temperature results in freezing into a metastable crystalline state with an intermediated unit cell between the room temperature crystalline phase and the smectic C phase. The understanding of such interfacial induced phases in thin semiconducting liquid crystal films allows tuning of crystallographic and therefore physical properties within organic thin films.