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Characterization of Nanostructured Semiconductors by Ultrafast Luminescence Imaging.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Characterization of Nanostructured Semiconductors by Ultrafast Luminescence Imaging./
Author:	Blake, Jolie.
Description:	1 online resource (167 pages)
Notes:	Source: Dissertation Abstracts International, Volume: 79-05(E), Section: B.
Contained By:	Dissertation Abstracts International79-05B(E).
Subject:	Chemistry. -
Online resource:	click for full text (PQDT)
ISBN:	9780355466133

Characterization of Nanostructured Semiconductors by Ultrafast Luminescence Imaging.
Blake, Jolie.

Characterization of Nanostructured Semiconductors by Ultrafast Luminescence Imaging. - 1 online resource (167 pages)

Source: Dissertation Abstracts International, Volume: 79-05(E), Section: B.

Thesis (Ph.D.)

Includes bibliographical references

Single nanostructures are predicted to be the building blocks of next generation devices and have already been incorporated into prototypes for solar cells, biomedical devices and lasers. Their role in such applications requires a fundamental understanding of their opto-electronic properties and in particular the charge carrier dynamics occurring on an ultrafast timescale. Luminescence detection is a common approach used to investigate electronic properties of nanostructures because of the contact-less nature of these methods. They are, however, often not equipped to efficiently measure multiple single nanostructures nor do they have the temporal resolution necessary for observing femtosecond dynamics. This dissertation intends to address this paucity of techniques available for the contact-less measurement of single nanostructures through the development of an ultrafast wide-field Kerr-gated microscope system and measurement technique. The setup, operational in both the steady state and transient mode and capable of microscopic and spectroscopic measurements, was developed to measure the transient luminescence of single semiconductor nanostructures. With sub micron spatial resolution and the potential to achieve a temporal resolution greater than 90 fs, the system was used to probe the charge carrier dynamics at multiple discrete locations on single nanowires exhibiting amplified spontaneous emission. Using a rate model for amplified spontaneous emission, the transient emission data was fitted to extract the values of the competing Shockley-Read-Hall, non-geminate and Auger recombination constants. The capabilities of the setup were first demonstrated in the visible detection range, where single nanowires of the ternary alloy CdS x Se1--x were measured. The temporal emission dynamics at two separate locations were compared and calculation of the Langevin mobility revealed that the large carrier densities generated in the nanowire allows access to non-diffusion controlled recombination. In the second phase of this study the setup was configured to the ultraviolet detection range for measuring the nanowires of conductive metal oxides. ZnO was the metal oxide of focus in this research. Ultrafast measurements were conducted on ZnO nanowires and ASE dynamics from multiple regions along a nanowire were again fitted to the ASE model and the recombination constants extracted. The diminished influence of the Shockley-Read-Hall recombination rate on the measured luminescence suggested that leading quadratic term in the model is a measure of a two-body defect mediated recombination rate, from which a defect density could be calculated. The measured change in defect density along the length of the nanowire correlated with changes in the growth conditions that established a defect gradient. The results show that the Kerr-gated system, as well as being a probe of ultrafast dynamics, is also a new tool for measuring changes in defect density in single nanostructures.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2018

Mode of access: World Wide Web

ISBN: 9780355466133Subjects--Topical Terms:

593913
Chemistry.
Index Terms--Genre/Form:

554714
Electronic books.

Characterization of Nanostructured Semiconductors by Ultrafast Luminescence Imaging.
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300 $a 1 online resource (167 pages)
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500 $a Source: Dissertation Abstracts International, Volume: 79-05(E), Section: B.
500 $a Adviser: Lars Gundlach.
502 $a Thesis (Ph.D.) $c University of Delaware $d 2017.
504 $a Includes bibliographical references
520 $a Single nanostructures are predicted to be the building blocks of next generation devices and have already been incorporated into prototypes for solar cells, biomedical devices and lasers. Their role in such applications requires a fundamental understanding of their opto-electronic properties and in particular the charge carrier dynamics occurring on an ultrafast timescale. Luminescence detection is a common approach used to investigate electronic properties of nanostructures because of the contact-less nature of these methods. They are, however, often not equipped to efficiently measure multiple single nanostructures nor do they have the temporal resolution necessary for observing femtosecond dynamics. This dissertation intends to address this paucity of techniques available for the contact-less measurement of single nanostructures through the development of an ultrafast wide-field Kerr-gated microscope system and measurement technique. The setup, operational in both the steady state and transient mode and capable of microscopic and spectroscopic measurements, was developed to measure the transient luminescence of single semiconductor nanostructures. With sub micron spatial resolution and the potential to achieve a temporal resolution greater than 90 fs, the system was used to probe the charge carrier dynamics at multiple discrete locations on single nanowires exhibiting amplified spontaneous emission. Using a rate model for amplified spontaneous emission, the transient emission data was fitted to extract the values of the competing Shockley-Read-Hall, non-geminate and Auger recombination constants. The capabilities of the setup were first demonstrated in the visible detection range, where single nanowires of the ternary alloy CdS x Se1--x were measured. The temporal emission dynamics at two separate locations were compared and calculation of the Langevin mobility revealed that the large carrier densities generated in the nanowire allows access to non-diffusion controlled recombination. In the second phase of this study the setup was configured to the ultraviolet detection range for measuring the nanowires of conductive metal oxides. ZnO was the metal oxide of focus in this research. Ultrafast measurements were conducted on ZnO nanowires and ASE dynamics from multiple regions along a nanowire were again fitted to the ASE model and the recombination constants extracted. The diminished influence of the Shockley-Read-Hall recombination rate on the measured luminescence suggested that leading quadratic term in the model is a measure of a two-body defect mediated recombination rate, from which a defect density could be calculated. The measured change in defect density along the length of the nanowire correlated with changes in the growth conditions that established a defect gradient. The results show that the Kerr-gated system, as well as being a probe of ultrafast dynamics, is also a new tool for measuring changes in defect density in single nanostructures.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2018
538 $a Mode of access: World Wide Web
650 4 $a Chemistry. $3 593913
650 4 $a Physics. $3 564049
650 4 $a Nanoscience. $3 632473
655 7 $a Electronic books. $2 local $3 554714
690 $a 0485
690 $a 0605
690 $a 0565
710 2 $a ProQuest Information and Learning Co. $3 1178819
710 2 $a University of Delaware. $b Department of Chemistry and Biochemistry. $3 1182502
773 0 $t Dissertation Abstracts International $g 79-05B(E).
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10615659 $z click for full text (PQDT)