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Organic thin-film transistors (OTFTs) based upon α,ω-dihexylsexithiophene (DH6T) have been fabricated and characterized. The DH6T thin films were prepared using neutral cluster beam deposition (NCBD) methods on room-temperature SiO2 substrates. The effects of surface modification were examined. The geometric effects of the gate dielectric thickness, channel length, and width on the device characteristics were also systematically studied. A combination of the NCBD technique and octadecyltrichlorosilane (OTS) pretreatment was most efficient for producing high-quality crystalline DH6T films. The temperature dependence of the field-effect mobility (μeff) indicated that the transistor performance was strongly correlated with the structural and morphological properties of the DH6T active layers and that the surfactant pretreatment significantly enhanced the μeff. A room-temperature μeff of 0.16cm2∕Vs for the OTS-pretreated transistors was found to be best so far reported for DH6T-based OTFTs using a SiO2 gate dielectric layer.

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: The production of adventitious roots derived from root explant of Echinacea angustifolia and its secondary metabolite content were assessed in different types and levels of auxin. The induction of adventitious roots from root explant cultured in Murashige and Skoog solid medium supplemented with 1.0 ㎎/L indole -3-butyric acid (IBA) attained highest as 20.87 ㎎ fresh weight and 3.07 ㎎ dry weight per culture but root suspension culture at the same concentration of IBA enhanced biomass production as 3.07 g fresh weight and 0.38 g per culture after 4 weeks in culture. 3.0 ㎎/L α-naphthalene acetic acid (NAA) treatment had similar effect on root biomass production as 3.07 g fresh weight and 0.38 g per culture with liquid suspension culture, whereas adventitious roots exposed to over 3.0-5.0 ㎎/L IBA or 5.0 ㎎/L NAA were less responsive by reducing the number of adventitious roots and/or changing root morphology such as short and thick. The content of secondary metabolites such as phenolic, flavonoids and total caffeic acid in adventitious roots cultured on MS medium supplemented with 1.0 ㎎/L IBA were attained highest as 27.20, 9.60. 10.67 ㎎/g dry weight, respectively. Overall, the best production of root biomass and secondary metabolites were given by 1.0 ㎎/L IBA.