title: Studies of tetracene- and pentacene-based organic thin-film transistors fabricated by the neutral cluster beam deposition method.
abstract: The neutral cluster beam deposition (NCBD) method has been applied to produce and characterize organic thin-film transistors (OTFTs) based upon tetracene and pentacene molecules as active layers. Organic thin films were prepared by the NCBD method on hexamethyldisilazane (HMDS)-untreated and -pretreated silicon dioxide (SiO2) substrates at room temperature. The surface morphology and structures for the tetracene and pentacene thin films were examined by atomic force microscopy (AFM) and X-ray diffraction (XRD). The measurements demonstrate that the weakly bound and highly directional neutral cluster beams are efficient in producing high-quality single-crystalline thin films with uniform, smooth surfaces and that SiO2 surface treatment with HMDS enhances the crystallinity of the pentacene thin-film phase. Tetracene- and pentacene-based OTFTs with the top-contact structure showed typical source-drain current modulation behavior with different gate voltages. Device parameters such as hole carrier mobility, current on/off ratio, threshold voltage, and subthreshold slope have been derived from the current-voltage characteristics together with the effects of surface treatment with HMDS. In particular, the high field-effect room-temperature mobilities for the HMDS-untreated OTFTs are found to be comparable to the most widely reported values for the respective untreated tetracene and pentacene thin-film transistors. The device performance strongly correlates with the surface morphology, and the structural properties of the organic thin films are discussed.
authors.affiliation: Department of Chemistry and Center for Electro- and Photo-Responsive Molecules, Korea University, Anam-Dong, Seoul 136-701, Korea.
authors.forename: P Syed
authors.initials: PS
authors.lastname: Abthagir
authors.forename: Young-Geun
authors.initials: YG
authors.lastname: Ha
authors.forename: Eun-Ah
authors.initials: EA
authors.lastname: You
authors.forename: Seon-Hwa
authors.initials: SH
authors.lastname: Jeong
authors.forename: Hoon-Seok
authors.initials: HS
authors.lastname: Seo
authors.forename: Jong-Ho
authors.initials: JH
authors.lastname: Choi