title: Interface induced crystal structures of dioctyl-terthiophene thin films.
abstract: 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-DOTT 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.
authors.affiliation: Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 810 Graz, Austria.
authors.forename: Oliver
authors.initials: O
authors.lastname: Werzer
authors.forename: Nicolas
authors.initials: N
authors.lastname: Boucher
authors.forename: Johann P
authors.initials: JP
authors.lastname: de Silva
authors.forename: Gabin
authors.initials: G
authors.lastname: Gbabode
authors.forename: Yves H
authors.initials: YH
authors.lastname: Geerts
authors.forename: Oleg
authors.initials: O
authors.lastname: Konovalov
authors.forename: Armin
authors.initials: A
authors.lastname: Moser
authors.forename: Jiri
authors.initials: J
authors.lastname: Novak
authors.forename: Roland
authors.initials: R
authors.lastname: Resel
authors.forename: Michele
authors.initials: M
authors.lastname: Sferrazza
mesh_terms: D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D018360:Crystallography, X-Ray; D050866:Liquid Crystals / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D008968:Molecular Conformation; D044367:Phase Transition; D012666:Semiconductors; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics; D013876:Thiophenes / Q000737:chemistry*
chemical_list: D013876:Thiophenes; D012822:Silicon Dioxide