title: High anisotropy of the field-effect transistor mobility in magnetically aligned discotic liquid-crystalline semiconductors.
abstract: A magnetic field has been utilized for producing highly oriented films of a substituted hexabenzocoronene (HBC). Optical microscopy studies revealed large area HBC monodomains that covered the entire film, while wide-angle X-ray measurements showed that the HBC molecules are aligned with their planes along the applied field. On the basis of this method, solution-processed field-effect transistors (FET) have been constructed with charge carrier mobilities of up to 10(-3) cm2/V.s, which are significantly enhanced with respect to the unaligned material. Exceptionally high mobility anisotropies of 25-75 for current flow parallel and perpendicular to the alignment direction have been measured as a function of the channel length. Atomic force microscopy performed on the FET structures reveals fibril superstructures that are oriented perpendicularly to the magnetic field direction, consisting of molecular columns with a slippage angle of 40 degrees between the molecules. For channel lengths larger than 2.5 mum, the fibrils are smaller than the electrode spacing, which adversely affects the device performance.
authors.affiliation: High Field Magnet Laboratory, Institute for Molecules and Materials, Radboud University Nijmegen, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
authors.forename: Igor O
authors.initials: IO
authors.lastname: Shklyarevskiy
authors.forename: Pascal
authors.initials: P
authors.lastname: Jonkheijm
authors.forename: Natalie
authors.initials: N
authors.lastname: Stutzmann
authors.forename: Dorothee
authors.initials: D
authors.lastname: Wasserberg
authors.forename: Harry J
authors.initials: HJ
authors.lastname: Wondergem
authors.forename: Peter C M
authors.initials: PC
authors.lastname: Christianen
authors.forename: Albertus P H J
authors.initials: AP
authors.lastname: Schenning
authors.forename: Dago M
authors.initials: DM
authors.lastname: de Leeuw
authors.forename: Zeljko
authors.initials: Z
authors.lastname: Tomović
authors.forename: Jishan
authors.initials: J
authors.lastname: Wu
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen
authors.forename: Jan C
authors.initials: JC
authors.lastname: Maan