Thermoelectric Transport Phenomena in Semiconducting Nanostructures

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dc.contributor.advisorRabin, Odeden_US
dc.contributor.authorCornett, Jane Elizabethen_US
dc.contributor.departmentMaterial Science and Engineeringen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2014-02-06T06:30:42Z
dc.date.available2014-02-06T06:30:42Z
dc.date.issued2013en_US
dc.description.abstractThe efficiencies of state-of-the-art thermoelectric devices made from bulk materials remain too low for widespread application. Early predictions by Hicks and Dresselhaus indicated that one potential route for improving the thermoelectric properties of materials was through nanostructuring. This predicted improvement was due to two effects: an increase in the thermoelectric power factor and a decrease in the lattice thermal conductivity. In this thesis, new models are developed for calculation of the thermoelectric transport properties of nanostructures. The results of these models are in line with what has been seen experimentally in the field of nanostructured thermoelectrics: the power factor of nanostructures falls below the bulk value for sizes accessible by current experimental techniques. While this is demonstrated first for a particular system (cylindrical InSb nanowires), this result is shown to hold true regardless of the dimensionality of the system, the material of interest or the temperature. Using the analytical forms of the transport properties of nanostructured systems, we derive universal scaling relations for the power factor which further point to the fundamental and general nature of this result. Calculations done for nanostructured systems in which the scattering time is a function of carrier energy indicate that the introduction of nanoscale grain boundaries can lead to improvements in the power factor. We present experimental methods for the fabrication and characterization of porous bismuth-antimony-telluride (Bi<sub>2-x</sub>Sb<sub>x</sub>Te<sub>3</sub>) thin films using a templated deposition technique. Preliminary results from this experimental work indicate that the nanostructured morphology of the templates used for the deposition of porous films limits diffusion during grain growth, and thus the crystal structure of these porous films differs from that of films deposited on dense substrates. For fundamental investigation of the effects of porosity on thermoelectric transport, future studies should therefore focus on Bi<sub>2-x</sub>Sb<sub>x</sub>Te<sub>3</sub> thin films made by top-down patterning techniques.en_US
dc.identifier.urihttp://hdl.handle.net/1903/14830
dc.language.isoenen_US
dc.subject.pqcontrolledEngineeringen_US
dc.subject.pquncontrolledBismuth antimony tellurideen_US
dc.subject.pquncontrolledInSben_US
dc.subject.pquncontrolledNanostructuresen_US
dc.subject.pquncontrolledNanowiresen_US
dc.subject.pquncontrolledThermoelectricen_US
dc.subject.pquncontrolledThin filmsen_US
dc.titleThermoelectric Transport Phenomena in Semiconducting Nanostructuresen_US
dc.typeDissertationen_US

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