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dc.contributor.advisorWu, Zhigang
dc.contributor.authorTwombly, Chris
dc.date.accessioned2016-01-14T16:51:06Z
dc.date.accessioned2022-02-03T12:51:26Z
dc.date.available2016-01-14T16:51:06Z
dc.date.available2022-02-03T12:51:26Z
dc.date.issued2015
dc.identifierT 7938
dc.identifier.urihttps://hdl.handle.net/11124/169997
dc.description2015 Fall.
dc.descriptionIncludes color illustrations.
dc.descriptionIncludes bibliographical references.
dc.description.abstractGraphene has very beneficial charge transport properties which make it an interesting potential thermoelectric material, but its thermoelectric efficiency is limited by large thermal conductivity. Nanostructuring graphene by incorporating periodic holes in the crystal structure produces graphene nanomesh with reduced thermal conductivity due to increased phonon scattering. The goal of this study was to investigate the thermoelectric properties of graphene nanomeshes and defected graphene using Density Functional Theory and semi-classical Boltzmann Transport Theory. We computed the Seebeck coefficient, electrical conductivity, and the electrical component of thermal conductivity from first principles. We first developed and verified the accuracy of our techniques using silicon. We then examined the properties of silicon nanowires in order to study systems with more complex geometry and to show that nanostructuring can improve thermoelectric properties. Our results agreed closely with previous experimental and theoretical studies of silicon systems. We then employed this suite of methods to study graphene, graphene nanomeshes, and periodically defected graphene. Our calculations for pristine graphene agreed closely with experimental measurements, proving that our methods work well with 2D systems. Our calculations suggest that there is up to a one order of magnitude increase in Seebeck coefficient for graphene nanomeshes compared to pristine graphene. This increase was found to be strongly dependent on a previously predicted geometrically based semimetal to semiconductor transition. We estimated a maximum ZT of 0.15-0.4 for graphene nanomeshes based on a simple scaling law for the thermal conductivity in these systems. The ZT value is strongly dependent on the purity and the quality of the graphene crystal lattice, which affects the relaxation time of charge carriers in these systems. We then studied defected graphene with partial hydrogen passivation and boron-nitride (BN) doping to further demonstrate the importance of the semimetal to semiconductor transition. We concluded that the geometrically based semimetal to semiconductor transition in graphene systems is responsible for improved thermoelectric properties, and helps explain strong disorder based reduction in efficiency reported in previous computational studies. Our study suggests that with further optimization nanostructured graphene could be a potential thermoelectric material.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado School of Mines. Arthur Lakes Library
dc.relation.ispartof2015 - Mines Theses & Dissertations
dc.rightsCopyright of the original work is retained by the author.
dc.subjectgraphene
dc.subjectgraphene nanomesh
dc.subjectperiodic defected graphene
dc.subjectthermoelectric
dc.titleStudy of thermoelectric properties of graphene materials, A
dc.typeText
dc.contributor.committeememberLusk, Mark T.
dc.contributor.committeememberWood, David M.
thesis.degree.nameMaster of Science (M.S.)
thesis.degree.levelMasters
thesis.degree.disciplinePhysics
thesis.degree.grantorColorado School of Mines


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