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dc.contributor.advisorStrzhemechny, Yuri M.
dc.contributor.authorPeters, Raul Mugabeen_US
dc.date.accessioned2014-07-22T18:48:07Z
dc.date.available2014-07-22T18:48:07Z
dc.date.created2010en_US
dc.date.issued2010en_US
dc.identifieretd-03282011-125929en_US
dc.identifierumi-10171en_US
dc.identifiercat-001666428en_US
dc.identifier.urihttps://repository.tcu.edu/handle/116099117/4262
dc.description.abstractThe surface of ZnO semiconductor nanosystems is a key performance-defining factor in numerous applications. In this work we present experimental results for the surface defect-related properties of ZnO nanoscale systems. Surface photovoltage spectroscopy was used to determine the defect level energies within the band gap, the conduction vs. valence band nature of the defect-related transitions, and to probe key dynamic parameters of the surface on a number of commercially available ZnO nanopowders. In our experimental setup, surface photovoltage characterization is conducted in high vacuum in tandem with in situ oxygen remote plasma treatments. Surface photovoltage investigations of the as-received and plasma-processed samples revealed a number of common spectral features related to surface states. Furthermore, we observed significant plasma-induced changes in the surface defect properties. Ex situ positron annihilation and photoluminescence measurements were performed on the studied samples and correlated with surface photovoltage results. The average positron lifetimes were found to be substantially longer than in a bulk single crystalline sample, which is consistent with the model of grains with defect-rich surface and subsurface layers. Compression of the powders into pellets yielded reduction of the average positron lifetimes. Surface photovoltage, positron annihilation, and photoluminescence spectra consistently showed sample-to-sample differences due to the variation in the overall quality of the nanopowders, which partially obscures observation of the scaling effects. However, the results demonstrated that our approach is efficient in detecting specific surface states in nanoscale ZnO specimens and in elucidating their nature.
dc.format.mediumFormat: Onlineen_US
dc.language.isoengen_US
dc.publisher[Fort Worth, Tex.] : Texas Christian University,en_US
dc.relation.ispartofTexas Christian University dissertationen_US
dc.relation.ispartofUMI thesis.en_US
dc.relation.ispartofTexas Christian University dissertation.en_US
dc.relation.requiresMode of access: World Wide Web.en_US
dc.relation.requiresSystem requirements: Adobe Acrobat reader.en_US
dc.subject.lcshNanostructured materials.en_US
dc.subject.lcshZinc oxide.en_US
dc.titleStudies of surface states in zinc oxide nanopowdersen_US
dc.typeTexten_US
etd.degree.departmentDepartment of Physics and Astronomy
etd.degree.levelDoctoral
local.collegeCollege of Science and Engineering
local.departmentPhysics and Astronomy
local.academicunitDepartment of Physics and Astronomy
dc.type.genreDissertation
local.subjectareaPhysics and Astronomy
etd.degree.nameDoctor of Philosophy
etd.degree.grantorTexas Christian University


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