EXPLORATION OF NOVEL METHODS FOR THE FABRICATION AND CHARACTERIZATION OF ORGANIC FIELD-EFFECT TRANSISTORS AND EXAMINATION OF FACTORS INFLUENCING OFET PERFORMANCE

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dc.contributor.advisorFuhrer, Michael S.en_US
dc.contributor.authorSouthard, Adrian Edwarden_US
dc.contributor.departmentChemical Physicsen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2010-02-19T06:49:13Z
dc.date.available2010-02-19T06:49:13Z
dc.date.issued2009en_US
dc.description.abstractThis thesis explores novel methods for fabricating organic field effect transistors (OFETs) and characterizing OFET devices. Transfer printing is a promising process for fabricating organic thin-film devices. In this work, a transfer-printing process is developed for the polymer organic semiconductor P3HT. Pre-patterned P3HT is printed onto different dielectrics such as PMMA, polystyrene and polycarbonate. The P3HT layer is spun on a smooth silicon interface made hydrophobic by treatment with octyltrichlorosilane, which functions as a release layer. This method has distinct advantages over standard OFET fabrication methods in that 1) the active layer can be pre-patterned, 2) the solvent for the P3HT need not be compatible with the target substrate, and 3) the electrical contact formed mimics the properties of top contacts but with the spatial resolution of bottom contacts. Transparent, conducting films of carbon nanotubes (CNTs) are prepared by airbrushing, and characterized optically and electronically. OFETs with CNT films as source and drain electrodes are fabricated using various patterning techniques, and the organic/CNT contact resistance is characterized. CNT films make transparent, flexible electrodes with contact resistance comparable to that found for Au bottom-contacted P3HT transistors and comparable to CNT-film bottom-contacted pentacene transistors with CNTs deposited by other less flexible methods. A transparent OFET is demonstrated using transfer printing for the assembly of an organic semiconductor (pentacene), CNT film source, drain, and gate electrodes, and polymer gate dielectric and substrate. The dependence of the conductance and mobility in pentacene OFETs on temperature, gate voltage, and source-drain electric field is studied. The data are analyzed by extending a multiple trapping and release model to account for lowering of the energy required to excite carriers into the valence band (Poole-Frenkel effect). The temperature-dependent conductivity shows activated behavior, and the activation energy is lowered roughly linearly with the square-root of electric field, as expected for the Poole-Frenkel effect. The gate voltage dependence of the activation energy is used to extract the trap density of states, in good agreement with other measurements in the literature.en_US
dc.identifier.urihttp://hdl.handle.net/1903/9897
dc.subject.pqcontrolledPhysics, Condensed Matteren_US
dc.subject.pqcontrolledNanoscienceen_US
dc.subject.pqcontrolledEngineering, Materials Scienceen_US
dc.subject.pquncontrolledcarbon nanotubesen_US
dc.subject.pquncontrolledfield-dependent mobilityen_US
dc.subject.pquncontrolledfield-effect transistorsen_US
dc.subject.pquncontrolledpentaceneen_US
dc.subject.pquncontrolledpoly(3-hexylthiophene)en_US
dc.subject.pquncontrolledtransparent electrodesen_US
dc.titleEXPLORATION OF NOVEL METHODS FOR THE FABRICATION AND CHARACTERIZATION OF ORGANIC FIELD-EFFECT TRANSISTORS AND EXAMINATION OF FACTORS INFLUENCING OFET PERFORMANCEen_US
dc.typeDissertationen_US

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