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The effect of electron-hole pairs in semiconductor and topological insulator nanostructures on plasmon resonances and photon polarizations.

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Date Issued:
2014
Abstract/Description:
The generation of electron-hole pairs in materials has great importance. In directbandgap semiconductor materials, the mechanism of radiative recombination of electron-holepairs leads to the emission of photons, which is the basis of Light Emitting Diodes(LEDs). The excitation of electron-hole pairs by absorption of photons is the active processin photodiodes, solar cells, and other semiconductor photodetector devices. In optoelectronicdevices such as optical switches which are based on transmission and reflection of the photons,electron-hole pairs excitation is a key for the device performance. Diodes and transistorsare also great discoveries in electronics which rely on the generation and recombination ofelectron-hole pairs at p-n junctions. In three-dimensional topological insulators (3D TIs)materials nanostructures excitation of electron-hole pairs can be utilized for the quantummemory, quantum information and quantum teleportation. In two-dimensional (2D) layeredmaterials like graphene, MoS_2, MoSe_2, WS_2 and WSe_2 generation and recombination ofelectron hole pairs is main process at p-n junctions, infrared detectors and sensors.This PhD thesis is concerned with the physics of different types of electron-hole pairsin various materials, such as wide-bandgap semiconductors, 3D topological insulators, andplasmonic excitations in metallic nanostructures. The materials of interest are wide bandgap semiconductors such as TiO_2 , 3D TIs such as Pb_1?xSn_xTe and the 2D layered materials such as MoS_2 and MoO_3. We study the electronic and optical properties in bulk and nanostructures and find applications in the area of semiclassical and quantum information processing. One of the interesting applications we focus in this thesis is shift in surface plasmon resonance due to reduction in index of refraction of surrounding dielectric environment which inturns shifts the wavelength of surface plasmon resonance up to 125 nm for carrier density of10^22/cm^3. Employing this effect, we present a model of a light controlled plasmon switching using a hybrid metal-dielectric heterostructures.In 3D TIs nanostructures, the time reversible spin partners in the valence and conductionband can be coupled by a left and a right handed circular polarization of the light.Such coupling of light with electron-hole pair polarization provides an unique opportunityto utilize 3D TIs in quantum information processing and spintronics devices. We present a model of a 3D TI quantum dot made of spherical core-bulk heterostructure. When a 3D TI QD is embedded inside a cavity, the single-photon Faraday rotation provides the possibility to implement optically mediated quantum teleportation and quantum information processing with 3D TI QDs, where the qubit is defined by either an electron-hole pair, a single electron spin, or a single hole spin in a 3D TI QD.Due to excellent transport properties in single and multiple layers of 2D layeredmaterials, several efforts have demonstrated the possibility to engineer electronic and optoelectronic devices based on MoS_2. In this thesis, we focus on theoretical and experimental study of electrical property and photoluminescence tuning, both in a single-layer of MoS_2.We present theoretical analysis of experimental results from the point of view of stability of MoO_3 defects in MoS_2 single layer and bandstructures calculation. In experiment, the electrical property of a single layer of MoS_2 can be tuned from semiconducting to insulating regime via controlled exposure to oxygen plasma. The quenching of photoluminescence of asingle sheet of MoS_2 has also been observed upon exposure to oxygen plasmas. We calculatethe direct to indirect band gap transitions by going from MoS_2 single sheet to MoO_3 singlesheet during the plasma exposure, which is due to the formation of MoO_3 rich defect domainsinside a MoS_2 sheet.
Title: The effect of electron-hole pairs in semiconductor and topological insulator nanostructures on plasmon resonances and photon polarizations.
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Name(s): Paudel, Hari, Author
Leuenberger, Michael, Committee Chair
Rahman, Talat, Committee Member
Saha, Haripada, Committee Member
Gesquiere, Andre, Committee Member
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2014
Publisher: University of Central Florida
Language(s): English
Abstract/Description: The generation of electron-hole pairs in materials has great importance. In directbandgap semiconductor materials, the mechanism of radiative recombination of electron-holepairs leads to the emission of photons, which is the basis of Light Emitting Diodes(LEDs). The excitation of electron-hole pairs by absorption of photons is the active processin photodiodes, solar cells, and other semiconductor photodetector devices. In optoelectronicdevices such as optical switches which are based on transmission and reflection of the photons,electron-hole pairs excitation is a key for the device performance. Diodes and transistorsare also great discoveries in electronics which rely on the generation and recombination ofelectron-hole pairs at p-n junctions. In three-dimensional topological insulators (3D TIs)materials nanostructures excitation of electron-hole pairs can be utilized for the quantummemory, quantum information and quantum teleportation. In two-dimensional (2D) layeredmaterials like graphene, MoS_2, MoSe_2, WS_2 and WSe_2 generation and recombination ofelectron hole pairs is main process at p-n junctions, infrared detectors and sensors.This PhD thesis is concerned with the physics of different types of electron-hole pairsin various materials, such as wide-bandgap semiconductors, 3D topological insulators, andplasmonic excitations in metallic nanostructures. The materials of interest are wide bandgap semiconductors such as TiO_2 , 3D TIs such as Pb_1?xSn_xTe and the 2D layered materials such as MoS_2 and MoO_3. We study the electronic and optical properties in bulk and nanostructures and find applications in the area of semiclassical and quantum information processing. One of the interesting applications we focus in this thesis is shift in surface plasmon resonance due to reduction in index of refraction of surrounding dielectric environment which inturns shifts the wavelength of surface plasmon resonance up to 125 nm for carrier density of10^22/cm^3. Employing this effect, we present a model of a light controlled plasmon switching using a hybrid metal-dielectric heterostructures.In 3D TIs nanostructures, the time reversible spin partners in the valence and conductionband can be coupled by a left and a right handed circular polarization of the light.Such coupling of light with electron-hole pair polarization provides an unique opportunityto utilize 3D TIs in quantum information processing and spintronics devices. We present a model of a 3D TI quantum dot made of spherical core-bulk heterostructure. When a 3D TI QD is embedded inside a cavity, the single-photon Faraday rotation provides the possibility to implement optically mediated quantum teleportation and quantum information processing with 3D TI QDs, where the qubit is defined by either an electron-hole pair, a single electron spin, or a single hole spin in a 3D TI QD.Due to excellent transport properties in single and multiple layers of 2D layeredmaterials, several efforts have demonstrated the possibility to engineer electronic and optoelectronic devices based on MoS_2. In this thesis, we focus on theoretical and experimental study of electrical property and photoluminescence tuning, both in a single-layer of MoS_2.We present theoretical analysis of experimental results from the point of view of stability of MoO_3 defects in MoS_2 single layer and bandstructures calculation. In experiment, the electrical property of a single layer of MoS_2 can be tuned from semiconducting to insulating regime via controlled exposure to oxygen plasma. The quenching of photoluminescence of asingle sheet of MoS_2 has also been observed upon exposure to oxygen plasmas. We calculatethe direct to indirect band gap transitions by going from MoS_2 single sheet to MoO_3 singlesheet during the plasma exposure, which is due to the formation of MoO_3 rich defect domainsinside a MoS_2 sheet.
Identifier: CFE0005397 (IID), ucf:50454 (fedora)
Note(s): 2014-08-01
Ph.D.
Sciences, Physics
Doctoral
This record was generated from author submitted information.
Subject(s): Plasmonic -- Topological Insulators -- 2D Layered Materials
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0005397
Restrictions on Access: public 2014-08-15
Host Institution: UCF

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