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dc.contributor.advisorWu, Judy Z
dc.contributor.authorDizon, Jonathan Reyes
dc.date.accessioned2009-08-31T03:15:52Z
dc.date.available2009-08-31T03:15:52Z
dc.date.issued2009-04-28
dc.date.submitted2009
dc.identifier.otherhttp://dissertations.umi.com/ku:10371
dc.identifier.urihttp://hdl.handle.net/1808/5460
dc.description.abstractIdentifying defects and non-superconducting regions in high-temperature superconductors (HTS) is of great importance because they limit the material's capability to carry higher current densities and serve as nucleation spots for "hot spots" that can evolve over time and drive a HTS from superconducting (SC) to normal state. A technique that combines near-field scanning microwave microscopy (NSMM) with transport measurement was developed to image defects and nonuniformities at room temperature and detect low-level dissipation at low temperatures. At room temperature, macroscopic and microscopic defects in both conducting and HTS films were clearly identified and imaged with adequate sensitivity and resolution. At low temperatures, low-level dissipation was detected by observing the NSMM's response during the HTS' transition from SC to normal state. Measuring the time-dependent self-heating effect due to a bias current at a fixed temperature provided insight into the dynamics of thermal instability due to hot-spot nucleation. When the HTS is far from the transition state, a bi-modal evolution of the thermal quench was observed beginning with a nucleation of a local hot spot followed by a spreading/coalescence of them via self-heating. When the HTS is brought closer to transition by increasing either temperature or bias current, this effect is diminished due to faster hot spot growth and continuous spread by self-heating. Observations were obtained for both the bulk and grain boundary regions of a HTS.
dc.format.extent127 pages
dc.language.isoEN
dc.publisherUniversity of Kansas
dc.rightsThis item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
dc.subjectCondensed matter physics
dc.subjectDefects
dc.subjectDissipation
dc.subjectGrain boundary
dc.subjectImaging
dc.subjectMicrowave microscopy
dc.subjectSuperconductors
dc.titleA Combined Near-field Scanning Microwave Microscope and Transport Measurement System for Characterizing Dissipation in Conducting and High-Tc Superconducting Films at Variable Temperature
dc.typeDissertation
dc.contributor.cmtememberHan, Siyuan
dc.contributor.cmtememberZhao, Hui
dc.contributor.cmtememberBaringer, Phil
dc.contributor.cmtememberJohnson, Carey K.
dc.thesis.degreeDisciplinePhysics & Astronomy
dc.thesis.degreeLevelPh.D.
kusw.oastatusna
kusw.oapolicyThis item does not meet KU Open Access policy criteria.
dc.rights.accessrightsopenAccess


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