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Investigations of Excitons in Metall...

Wladkowski, Henry V.

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Investigations of Excitons in Metallic Single-Wall Carbon Nanotubes Using Terahertz Spectroscopy.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Investigations of Excitons in Metallic Single-Wall Carbon Nanotubes Using Terahertz Spectroscopy./
作者:	Wladkowski, Henry V.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
面頁冊數:	205 p.
附註:	Source: Dissertations Abstracts International, Volume: 82-12, Section: B.
Contained By:	Dissertations Abstracts International82-12B.
標題:	Condensed matter physics. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28315460
ISBN:	9798505586259

Investigations of Excitons in Metallic Single-Wall Carbon Nanotubes Using Terahertz Spectroscopy.
Wladkowski, Henry V.

Investigations of Excitons in Metallic Single-Wall Carbon Nanotubes Using Terahertz Spectroscopy. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 205 p.

Source: Dissertations Abstracts International, Volume: 82-12, Section: B.

Thesis (Ph.D.)--University of Wyoming, 2021.

This item must not be sold to any third party vendors.

Excitons, bound electron-hole pairs mediated through Coulomb interactions, are common in bulk and quantum-confined semiconductors, but are rarely observed in bulk metals.Recent measurements of quantum-confined metals have revealed the presence of excitons, notably in metallic single-wall carbon nanotubes (SWCNTs).Similar to atomic systems, excitons have hydrogenic internal energy levels, singlet and triplet states at different energies, and specific to SWCNTs a single, optically bright transition amongst 15 other dark, non-radiative, transitions.Despite interest in many-body effects that should be present in metallic excitons, key properties, such as formation dynamics and intra-excitonic transitions, have not yet been observed in metallic SWCNTs.In this thesis, I study one-dimensional excitons in near-single-chirality metallic SWCNTs.To enrich metallic SWCNTs, I use aqueous two-phase extraction to create high-purity, near-single-chirality metallic samples from nanotube mixtures.Additional world-class high-purity metallic SWCNT samples made using this method were provided for this study as well.Using a polymer matrix, I produce dry, solid, robust, optical and terahertz transparent, thin films containing SWCNTs that can maintain individualized carbon nanotube properties while withstanding experimental extremes of temperature, magnetic field, and applied laser power.Optimization of this polymer provides an avenue for cheap, facile, flexible, and quick solid sample preparation for multiple aqueous nanoparticle systems, including both SWCNTs and Au nanoparticles.Since far-infrared optical capabilities did not exist at the University of Wyoming, I designed, built, and tested a terahertz (THz) time-domain spectroscopy system.I demonstrate the THz system capabilities by spectrally resolving a metallic SWCNT THz absorption peak at both 297 K and 75 K, providing support for the low-energy plasmon interpretation of this feature.Given the uniqueness of this system at the University of Wyoming, I also worked on a separate effort determining the photoconductivity of Li intercalated WO_2Cl_2 samples.To observe exciton absorption features I redesigned, rebuilt, and retested an optical-pump, terahertz probe system from the terahertz time-domain spectroscopy system.Observations of absorption features from populated excitons in a thin film incorporating high-purity metallic SWCNTs were made on this expanded system.From these measurements, I determined a faint pump-induced absorption feature around 2.4 THz that could be caused by intra-excitonic transitions arising from internal energy levels, bright and dark states, or spin singlet and triplet states.Based on existing predictions, internal energy levels appear to be the most likely explanation for these transitions.My work here showing a reproducible, unambiguous optical-pump, terahertz probe absorption feature at room temperature in highly enriched well sorted metallic SWCNTs represents a significant step towards understanding the intra-excitonic transitions, formation times, and decay times of excitons in one-dimensional metallic systems.

ISBN: 9798505586259Subjects--Topical Terms:

3173567
Condensed matter physics.
Subjects--Index Terms:

Exciton

Investigations of Excitons in Metallic Single-Wall Carbon Nanotubes Using Terahertz Spectroscopy.
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506 $a This item must not be sold to any third party vendors.
520 $a Excitons, bound electron-hole pairs mediated through Coulomb interactions, are common in bulk and quantum-confined semiconductors, but are rarely observed in bulk metals.Recent measurements of quantum-confined metals have revealed the presence of excitons, notably in metallic single-wall carbon nanotubes (SWCNTs).Similar to atomic systems, excitons have hydrogenic internal energy levels, singlet and triplet states at different energies, and specific to SWCNTs a single, optically bright transition amongst 15 other dark, non-radiative, transitions.Despite interest in many-body effects that should be present in metallic excitons, key properties, such as formation dynamics and intra-excitonic transitions, have not yet been observed in metallic SWCNTs.In this thesis, I study one-dimensional excitons in near-single-chirality metallic SWCNTs.To enrich metallic SWCNTs, I use aqueous two-phase extraction to create high-purity, near-single-chirality metallic samples from nanotube mixtures.Additional world-class high-purity metallic SWCNT samples made using this method were provided for this study as well.Using a polymer matrix, I produce dry, solid, robust, optical and terahertz transparent, thin films containing SWCNTs that can maintain individualized carbon nanotube properties while withstanding experimental extremes of temperature, magnetic field, and applied laser power.Optimization of this polymer provides an avenue for cheap, facile, flexible, and quick solid sample preparation for multiple aqueous nanoparticle systems, including both SWCNTs and Au nanoparticles.Since far-infrared optical capabilities did not exist at the University of Wyoming, I designed, built, and tested a terahertz (THz) time-domain spectroscopy system.I demonstrate the THz system capabilities by spectrally resolving a metallic SWCNT THz absorption peak at both 297 K and 75 K, providing support for the low-energy plasmon interpretation of this feature.Given the uniqueness of this system at the University of Wyoming, I also worked on a separate effort determining the photoconductivity of Li intercalated WO_2Cl_2 samples.To observe exciton absorption features I redesigned, rebuilt, and retested an optical-pump, terahertz probe system from the terahertz time-domain spectroscopy system.Observations of absorption features from populated excitons in a thin film incorporating high-purity metallic SWCNTs were made on this expanded system.From these measurements, I determined a faint pump-induced absorption feature around 2.4 THz that could be caused by intra-excitonic transitions arising from internal energy levels, bright and dark states, or spin singlet and triplet states.Based on existing predictions, internal energy levels appear to be the most likely explanation for these transitions.My work here showing a reproducible, unambiguous optical-pump, terahertz probe absorption feature at room temperature in highly enriched well sorted metallic SWCNTs represents a significant step towards understanding the intra-excitonic transitions, formation times, and decay times of excitons in one-dimensional metallic systems.
590 $a School code: 0264.
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650 4 $a Optics. $3 517925
650 4 $a Nanoscience. $3 587832
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