ingest cdrApp 2019-01-04T14:54:54.472Z 2a9effba-8beb-4434-9ac1-3dd15c1ac330 modifyDatastreamByValue RELS-EXT fedoraAdmin 2019-01-04T14:55:52.839Z Setting exclusive relation addDatastream MD_TECHNICAL fedoraAdmin 2019-01-04T14:56:05.566Z Adding technical metadata derived by FITS addDatastream MD_FULL_TEXT fedoraAdmin 2019-01-04T14:56:32.126Z Adding full text metadata extracted by Apache Tika modifyDatastreamByValue RELS-EXT fedoraAdmin 2019-01-04T14:56:56.867Z Setting exclusive relation modifyDatastreamByValue MD_DESCRIPTIVE cdrApp 2019-01-22T16:05:07.222Z modifyDatastreamByValue MD_DESCRIPTIVE cdrApp 2019-03-20T14:23:47.205Z Erika Van Goethem Author Department of Chemistry College of Arts and Sciences IMAGING CHARGE CARRIER AND ACOUSTIC PHONON DYNAMICS IN SEMICONDUCTOR NANOMATERIALS USING ULTRAFAST PUMP-PROBE MICROSCOPY Future advancement of nanotechnology is dependent on our capabilities to design novel and ever increasingly complex nanomaterials. In order to manipulate the electronic and optical properties of these materials in an efficient way, we need a fundamental understanding of the physics of how structural features alter the properties of these nanomaterials. Nanostructures that are produced under identical conditions can have vastly different properties, and they can even have variations among different spatial locations within the same structure. This heterogeneity can have a significant impact on the properties, dynamics, and performance of nanoscale devices. As a result, it is important to understand dynamics in individual nanostructures. Most analytical techniques, however, probe dynamics in an ensemble of structures and thereby obscuring dynamics and making quantitative conclusions difficult. Pump-probe microscopy overcomes these limitations by combining the high-temporal resolution of pump-probe spectroscopy and the high-spatial resolution of optical microscopy. With combined spatial and temporal resolution, the microscope collects data from spatially distinct locations on individual nanostructures with a high throughput. Additionally, using computer controlled scanning mirrors with the microscope allows us to spatially separate the excitation and probe spots at the sample to allow the direct visualization of charge carrier and acoustic lattice motion on the nanoscale without the need for physical contact or active electrical connection. Here, this microscope has been used to image electron diffusion and thermal transport, as well as acoustic phonon propagation in germanium nanowires. Additionally, it has been employed to study exciton and free charge carrier dynamics in tungsten disulfide and tungsten diselenide nanoflakes. The propagation of a shear mode is captured in suspended tungsten diselenide nanoflakes using the spatially-separated pump-probe imaging configuration. Winter 2018 2018 Chemistry Exciton-polariton Dynamics, Phonon Transport, Semiconductor Nanowires, Thermal Conductivity, Transition Metal Dichalcogenides, Ultrafast Microscopy eng Doctor of Philosophy Dissertation University of North Carolina at Chapel Hill Graduate School Degree granting institution Chemistry John Papanikolas Thesis advisor Joanna Atkin Thesis advisor James Cahoon Thesis advisor Andrew Moran Thesis advisor Scott Warren Thesis advisor text Erika Van Goethem Creator Department of Chemistry College of Arts and Sciences IMAGING CHARGE CARRIER AND ACOUSTIC PHONON DYNAMICS IN SEMICONDUCTOR NANOMATERIALS USING ULTRAFAST PUMP-PROBE MICROSCOPY Future advancement of nanotechnology is dependent on our capabilities to design novel and ever increasingly complex nanomaterials. In order to manipulate the electronic and optical properties of these materials in an efficient way, we need a fundamental understanding of the physics of how structural features alter the properties of these nanomaterials. Nanostructures that are produced under identical conditions can have vastly different properties, and they can even have variations among different spatial locations within the same structure. This heterogeneity can have a significant impact on the properties, dynamics, and performance of nanoscale devices. As a result, it is important to understand dynamics in individual nanostructures. Most analytical techniques, however, probe dynamics in an ensemble of structures and thereby obscuring dynamics and making quantitative conclusions difficult. Pump-probe microscopy overcomes these limitations by combining the high-temporal resolution of pump-probe spectroscopy and the high-spatial resolution of optical microscopy. With combined spatial and temporal resolution, the microscope collects data from spatially distinct locations on individual nanostructures with a high throughput. Additionally, using computer controlled scanning mirrors with the microscope allows us to spatially separate the excitation and probe spots at the sample to allow the direct visualization of charge carrier and acoustic lattice motion on the nanoscale without the need for physical contact or active electrical connection. Here, this microscope has been used to image electron diffusion and thermal transport, as well as acoustic phonon propagation in germanium nanowires. Additionally, it has been employed to study exciton and free charge carrier dynamics in tungsten disulfide and tungsten diselenide nanoflakes. The propagation of a shear mode is captured in suspended tungsten diselenide nanoflakes using the spatially-separated pump-probe imaging configuration. 2018 2018-12 Chemistry Exciton-polariton Dynamics; Phonon Transport; Semiconductor Nanowires; Thermal Conductivity; Transition Metal Dichalcogenides; Ultrafast Microscopy eng Doctor of Philosophy Dissertation University of North Carolina at Chapel Hill Graduate School Degree granting institution Chemistry John Papanikolas Thesis advisor Joanna Atkin Thesis advisor James Cahoon Thesis advisor Andrew Moran Thesis advisor Scott Warren Thesis advisor text Erika Van Goethem Creator Department of Chemistry College of Arts and Sciences Future advancement of nanotechnology is dependent on our capabilities to design novel and ever increasingly complex nanomaterials. In order to manipulate the electronic and optical properties of these materials in an efficient way, we need a fundamental understanding of the physics of how structural features alter the properties of these nanomaterials. Nanostructures that are produced under identical conditions can have vastly different properties, and they can even have variations among different spatial locations within the same structure. This heterogeneity can have a significant impact on the properties, dynamics, and performance of nanoscale devices. As a result, it is important to understand dynamics in individual nanostructures. Most analytical techniques, however, probe dynamics in an ensemble of structures and thereby obscuring dynamics and making quantitative conclusions difficult. Pump-probe microscopy overcomes these limitations by combining the high-temporal resolution of pump-probe spectroscopy and the high-spatial resolution of optical microscopy. With combined spatial and temporal resolution, the microscope collects data from spatially distinct locations on individual nanostructures with a high throughput. Additionally, using computer controlled scanning mirrors with the microscope allows us to spatially separate the excitation and probe spots at the sample to allow the direct visualization of charge carrier and acoustic lattice motion on the nanoscale without the need for physical contact or active electrical connection. Here, this microscope has been used to image electron diffusion and thermal transport, as well as acoustic phonon propagation in germanium nanowires. Additionally, it has been employed to study exciton and free charge carrier dynamics in tungsten disulfide and tungsten diselenide nanoflakes. The propagation of a shear mode is captured in suspended tungsten diselenide nanoflakes using the spatially-separated pump-probe imaging configuration. 2018 2018-12 Chemistry Exciton-polariton Dynamics; Phonon Transport; Semiconductor Nanowires; Thermal Conductivity; Transition Metal Dichalcogenides; Ultrafast Microscopy eng Doctor of Philosophy Dissertation University of North Carolina at Chapel Hill Graduate School Degree granting institution John Papanikolas Thesis advisor Joanna Atkin Thesis advisor James Cahoon Thesis advisor Andrew Moran Thesis advisor Scott Warren Thesis advisor text VanGoethem_unc_0153D_18240.pdf uuid:34e6dec2-d876-4af7-8c0d-402d17b1e5c2 2020-12-31T00:00:00 2018-11-29T22:27:56Z proquest application/pdf 4160081