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Charge Transport and Transfer at the Nanoscale Between Metals and Novel Conjugated Materials

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dc.contributor.advisor Natelson, Douglas
dc.creator Worne, Jeffrey
dc.date.accessioned 2012-09-06T04:23:08Z
dc.date.accessioned 2012-09-06T04:23:25Z
dc.date.available 2012-09-06T04:23:08Z
dc.date.available 2012-09-06T04:23:25Z
dc.date.created 2012-05
dc.date.issued 2012-09-05
dc.date.submitted May 2012
dc.identifier.uri http://hdl.handle.net/1911/64670
dc.description.abstract Abstract Organic semiconductors (OSCs) and graphene are two classes of conjugated materials that hold promise to create flexible electronic displays, high speed transistors, and low-cost solar cells. Crucial to understanding the behavior of these materials is understanding the effects metallic contacts have on the local charge environment. Additionally, characterizing the charge carrier transport behavior within these materials sheds light on the physical mechanisms behind transport. The first part of this thesis examines the origin of the low-temperature, high electric field transport behavior of OSCs. Two chemically distinct OSCs are used, poly-3(hexylthiophene) (P3HT) and 6,13- bis(triisopropyl-silylethynyl) (TIPS) pentacene. Several models explaining the low-temperature behavior are presented, with one using the Tomonaga-Luttinger liquid (TLL) insulator-to-metal transition model and one using a field-emission hopping model. While the TLL model is only valid for 1-dimensional systems, it is shown to work for both P3HT (1D) and TIPS-pentacene (2D), suggesting the TLL model is not an appropriate description of these systems. Instead, a cross-over from thermally-activated hopping to field-emission hopping is shown to explain the data well. The second part of this thesis focuses on the interaction between gold and platinum contacts and graphene using suspended graphene over sub-100 nanometer channels. Contacts to graphene can strongly dominate charge transport and mobility as well as significantly modify the charge environment local to the contacts. Platinum electrodes are discovered to be strong dopants to graphene at short length scales while gold electrodes do not have the same effect. By increasing the separation distance between the electrodes, this discrepancy is shown to disappear, suggesting an upper limit on charge diffusion from the contacts. Finally, this thesis will discuss a novel technique to observe the high-frequency behavior in OSCs using two microwave sources and an organic transistor as a mixer. A theoretical model motivating this technique is presented which suggests the possibility of retrieving gigahertz charge transport phenomena at kilohertz detection frequencies. The current state of the project is presented and discrepancies between devices made with gold and platinum electrodes measured in the GHz regime are discussed.
dc.format.mimetype application/pdf
dc.language.iso eng
dc.subject graphene
organic semiconductor
nanoscale
PhD thesis
charge transport
P3HT
pentacene
dc.title Charge Transport and Transfer at the Nanoscale Between Metals and Novel Conjugated Materials
dc.contributor.committeeMember Kelly, Kevin F.
dc.contributor.committeeMember Mittleman, Daniel
dc.date.updated 2012-09-06T04:23:25Z
dc.identifier.slug 123456789/ETD-2012-05-135
dc.type.genre thesis
dc.type.material text
thesis.degree.department Electrical and Computer Engineering
thesis.degree.discipline Electrical and Computer Engineering
thesis.degree.grantor Rice University
thesis.degree.level Doctoral
thesis.degree.name Doctor of Philosophy
dc.identifier.citation Worne, Jeffrey. (2012) "Charge Transport and Transfer at the Nanoscale Between Metals and Novel Conjugated Materials." Doctoral Thesis, Rice University. http://hdl.handle.net/1911/64670.

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