Дисертації з теми "Nanostructured Semiconductors Crystals"
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Xavier, Paulo Adriano. "Estudos espectroscópicos e de dopagem de nanocristais semicondutores de ZnS com íons Co2+ Cu2+." Pós-Graduação em Química, 2013. https://ri.ufs.br/handle/riufs/6110.
Повний текст джерелаNo presente trabalho foram estudados nanocristais semicondutores, tambem conhecidos como pontos quanticos ou quantum dots, selecionando-se especificamente o sulfeto de zinco (ZnS). Foram utilizados ois diferentes agentes estabilizantes (glutationa e N-acetil-L-cisteina) na obtencao de nanocristais de ZnS por via aquosa. Buscou-se avaliar, especificamente, a eficiencia dos agentes tiois na estabilizacao das suspensoes de nanocristais frente a agregacao, no controle e distribuicao de tamanhos das particulas, bem como nas propriedades opticas. Estudou-se, alem disto, o efeito da dopagem com ions de metais de transicao (Cu2+ e Co2+) nas propriedades de fluorescencia. Por fim, foi avaliada a possibilidade de transferencia de energia entre os nanocristais semicondutores dopados e o corante safranina. Os nanocristais semicondutores de ZnS estabilizados por glutationa e por N-acetil-L-cisteina foram obtidos com tamanhos abaixo de 5 nm, formas aproximadamente esfericas e livres de agregacao, evidenciando que ambos agentes ii estabilizantes foram eficientes. Ambos agentes estabilizantes levaram a formacao de nanocristais com emissoes na regiao do azul, caracteristicas do envolvimento de estados de defeito de superficie do ZnS. No entanto, as amostras preparadas com glutationa apresentaram maiores intensidades de fluorescencia, quando comparadas com aquelas preparadas com N-acetil-L-cisteina. A dopagem dos nanocristais semicondutores ZnS/Glu com ions cobre e cobalto teve um efeito de diminuir as intensidades de fluorescencia dependente da concentracao nominal dos dopantes em ambos os casos, sugerindo que o cobalto atua de modo analogo ao cobre. Considerando-se tanto o efeito sobre as intensidades de emissao do ZnS quanto a ausencia de transicoes d-d do metal, o estudo sugeriu que a dopagem reduz a concentracao de vacancias de cations, bem como o envolvimento de pelo menos um dos estados eletronicos do cobalto nos processos de transicao. Nao se observou variacoes nos comprimentos de onda para diferentes concentracoes dos dopantes, provavelmente pela ausencia de interferencia no tamanho dos nanocristais semicondutores formados. Por fim, o estudo preliminar da supressao de fluorescencia dos nanocristais semicondutores pelo efeito de diferentes concentracoes do corante safranina mostrou que concentracoes significativamente baixas do corante foram suficientes para diminuir a intensidade de fluorescencia. Diferentes componentes das bandas de emissao dos nanocristais semicondutores foram influenciados de modo distinto. A analise dos dados pelos graficos de Stern-Volmer sugeriu a ocorrencia de mais de um processo de transferencia (energia e/ou eletrons). Este estudo sera aprofundado nos trabalhos futuros.
Ye, Wei. "Nano-epitaxy modeling and design: from atomistic simulations to continuum methods." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50304.
Повний текст джерелаLi, Fang. "Microstructural properties of semiconductor nanostructures." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:396024e1-a646-40ca-8212-cad925b18311.
Повний текст джерелаWilson, Daniel W. "Optical waveguiding in photorefractive crystals : photoinduced polarization conversion and electron waveguiding in semiconductor nanostructures : modes, directional coupling, and discontinuities." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/14934.
Повний текст джерелаMartin, Aude. "Nonlinear Photonic Nanostructures based on Wide Gap Semiconductor Compounds." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS526/document.
Повний текст джерелаThe energy consumption of the whole ICT ecosystem is growing at a fast paceand in a global context of the search for an ever more connected yet sustainable society, a technologicalbreakthrough is desired. Here, integrated nonlinear photonics will help by providingnovel possibilities for energy efficient signal processing. In this PhD thesis, I have been investigatingsub-wavelength semiconductor structures, particularly photonic crystals, which have shownremarkable nonlinear properties. More specifically the strong confinement and slow light propagationenables on-chip ultra-fast all-optical signal processing, either based on four-wave-mixingor self-phase modulation. The main point here is the use of novel semiconductor materials withimproved nonlinear properties with respect to Silicon. In fact, it has now been acknowledgedthat the nonlinear and free-carriers absorption in Silicon integrated photonic structures is anissue hindering the full exploitation of nonlinear effects. In my thesis, wide-gap III-V semiconductorshave been used to develop high quality photonic crystal waveguides and cavities whichare able to sustain extremely high optical power densities as well as large average power levels.I have demonstrated PhC waveguides with much improved thermal conductivity through heterogeneousintegration of GaInP membranes with silicon dioxide. This will allow continuous wave phase-sensitive amplification, which I already demonstrated in the pulsed regime using GaInPself-suspended membranes. In parallel, I have demonstrated high quality PhC in Gallium Phosphide,which is a very promising material because of the large bandgap and the very good thermalconductivity. Preliminar results demonstrate the achievement of extremely large nonlinear regime(mini-comb, soliton compression and fission ...)
Yong, Chaw Keong. "Ultrafast carrier dynamics in organic-inorganic semiconductor nanostructures." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:b2efdc6a-1531-4d3f-8af1-e3094747434c.
Повний текст джерелаGoh, Wui Hean. "Selective area growth and characterization of GaN based nanostructures by metal organic vapor phase epitaxy." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47720.
Повний текст джерелаEl, Barraj Ali. "Growth and electro-thermomigration on semiconductor surfaces by low energy electron microscopy." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0393.
Повний текст джерелаThis thesis is focused on the study of the growth, electromigration and thermomigration of nanostructures on the surface of semiconductors such as Si(100), Si(111) and Ge(111). On an experimental viewpoint, Low Energy Electron Microscopy (LEEM) allows us to access to the dynamics of the phenomena in situ and in real time. We have studied under electromigration and thermomigration the motions of 2D monoatomic holes and islands on the Si (100) surface. We have shown that diffusion anisotropy due to (2x1) and (1x2) surface reconstructions can affect the direction of motion of nanostructures. We have also studied electromigration and thermomigration of Si (111) surface. We show that 2D-(1x1) holes in the (7x7) phase move in the direction opposite to the electric current, while in the direction of the thermal gradient. We have obtained the effective charge and the Soret coefficient of Si atoms in presence of an electric current and a thermal gradient. At last, the nucleation, growth and dynamic coalescence of Au droplets on Au/Ge(111) surface is studied, and the electromigration of 2D Au/Ge(111)-( √3x√3) domains on Au/Ge(111)-(1x1) surface
Wu, Yimin A. "Towards large area single crystalline two dimensional atomic crystals for nanotechnology applications." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:bdb827e5-f3fd-4806-8085-0206e67c7144.
Повний текст джерелаWidmann, Frédéric. "Epitaxie par jets moléculaires de GaN, AlN, InN et leurs alliages : physique de la croissance et réalisation de nanostructures." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10234.
Повний текст джерелаWei, Chih-Ming, and 魏志銘. "Novel physical properties induced by nanostructured semiconductors, photonic crystals, surface plasmons, and magnetic materials." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/12443517868836870523.
Повний текст джерела國立臺灣大學
物理研究所
99
In this dissertation, we have reported the novel physical properties in the composites consisting of nanostructured semiconductors, photonic crystals (PCs), surface plasmons, and magnetic materials. The results can be divided into four parts which are spin transport in Si0.5Ge0.5/Si multiple quantum wells (MQWs), enhancement of luminescence extraction in Si0.5Ge0.5/Si MQWs by using PCs, manipulation of localized surface plasmon resonance (LSPR) by applying magnetic fields, and magnetoelectric (ME) effect in the composite consisting of piezoelectric semiconductors and ferromagnetic materials. In the first part, we have studied the properties of spin transport in Si0.5Ge0.5/Si MQWs. Circular photogalvanic effect (CPGE) and linear photogalvanic effect for interband transition have been observed simultaneously in Si0.5Ge0.5/Si MQWs. The signature of the CPGE is evidenced by the change of its sign upon reversing the radiation helicity. It is found that the observed CPGE photocurrent is an order of magnitude greater than that obtained for intersubband transition. The dependences of the CPGE on the angle of incidence and the excitation intensities can be well interpreted based on its characteristics. The large signal of spin generation observed here at room temperature should be very useful for the realization of practical application of spintronics. In the second part, we have successfully achieved the selective enhancement and suppression of the photoluminescence (PL) arising from Si0.5Ge0.5/Si MQWs by PCs. The formation of the stop band in PCs is designed to be a filter as well as a reflector. It is found that the self-assembled PCs are able to selectively enhance the luminescence of the type-II transitions at the interface between Si and Si0.5Ge0.5/Si layers and suppress the emission from Si. Our working principle shown here can be extended to many other material systems, and should be very useful for creating high power solid-state emitters. In the third part, magnetically tunable LSPR based on the composite consisting of noble metal nanoparticles and a ferromagnetic thin film have been demonstrated. It is found that both of the frequency and linewidth of the LSPR can be manipulated by applying an external magnetic field. The underlying mechanism is attributed to the variation of the dielectric constant in the ferromagnetic thin film resulted from the change of the magnetization. Our result shown here paves an alternative route to manipulate the characteristics of LSPR, which may be served as a new design concept for the development of magneto-optical devices. In the final part, The ME effect has been demonstrated based on the composite of the InGaN/GaN MQWs and the FeCo thin film. By applying an external magnetic field, the ferromagnetic layer will be deformed due to magnetostriction. This deformation is transmitted to the piezoelectric layers and results in piezoelectric effect, which induces electric polarization in the piezoelectric layers. The induced electric polarization changes the strain and the built-in internal electric field in the InGaN/GaN MQWs and therefore the optical properties of the InGaN/GaN MQWs change. The results shown here open up a possibility for the application of nitride semiconductors in magneto-optical and ME engineering. The novel phenomena discovered in this dissertation provides a more detailed understanding and potential applications of the composites consisting of semiconductor nanostructures, PCs, surface plasmons, and magnetic materials.
Panzarella, Tracy Heckler. "Synthesis of doped semiconductor nanostructures using microemulsions and liquid crystals as templates." 2010. https://scholarworks.umass.edu/dissertations/AAI3427563.
Повний текст джерелаKaranikolos, Georgios. "Templating the synthesis of compound semiconductor nanostructures using microemulsions and lyotropic liquid crystals." 2005. http://wwwlib.umi.com/dissertations/fullcit/3185311.
Повний текст джерелаTitle from PDF title page (viewed on Feb. 24, 2006) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Triantafyllos J. Mountziaris, Paschalis Alexandridis. Includes bibliographical references.
Ghane, Parvin. "Fabrication and analysis of CIGS nanoparticle-based thin film solar cells." 2013. http://hdl.handle.net/1805/3697.
Повний текст джерелаFabrication and analysis of Copper Indium Gallium di-Selenide (CIGS) nanoparticles-based thin film solar cells are presented and discussed. This work explores non-traditional fabrication processes, such as spray-coating for the low-cost and highly-scalable production of CIGS-based solar cells. CIGS nanoparticles were synthesized and analyzed, thin CIGS films were spray-deposited using nanoparticle inks, and resulting films were used in low-cost fabrication of a set of CIGS solar cell devices. This synthesis method utilizes a chemical colloidal process resulting in the formation of nanoparticles with tunable band gap and size. Based on theoretical and experimental studies, 100 nm nanoparticles with an associated band gap of 1.33 eV were selected to achieve the desired film characteristics and device performances. Scanning electron microcopy (SEM) and size measurement instruments (Zetasizer) were used to study the size and shape of the nanoparticles. Electron dispersive spectroscopy (EDS) results confirmed the presence of the four elements, Copper (Cu), Indium (In), Gallium (Ga), and Selenium (Se) in the synthesized nanoparticles, while X-ray diffraction (XRD) results confirmed the tetragonal chalcopyrite crystal structure. The ultraviolet-visible-near infra-red (UV-Vis-NIR) spectrophotometry results of the nanoparticles depicted light absorbance characteristics with good overlap against the solar irradiance spectrum. The depositions of the nanoparticles were performed using spray-coating techniques. Nanoparticle ink dispersed in ethanol was sprayed using a simple airbrush tool. The thicknesses of the deposited films were controlled through variations in the deposition steps, substrate to spray-nozzle distance, size of the nozzle, and air pressure. Surface features and topology of the spray-deposited films were analyzed using atomic force microscopy (AFM). The deposited films were observed to be relatively uniform with a minimum thickness of 400 nm. Post-annealing of the films at various temperatures was studied for the photoelectric performance of the deposited films. Current density and voltage (J/V) characteristics were measured under light illumination after annealing at different temperatures. It was observed that the highest photoelectric effect resulted in annealing temperatures of 150-250 degree centigrade under air atmosphere. The developed CIGS films were implemented in solar cell devices that included Cadmium Sulfide (CdS) and Zinc Oxide (ZnO) layers. The CdS film served as the n-type layer to form a pn junction with the p-type CIGS layer. In a typical device, a 300 nm CdS layer was deposited through chemical bath deposition on a 1 $mu$m thick CIGS film. A thin layer of intrinsic ZnO was spray coated on the CdS film to prevent shorting with the top conductor layer, 1.5 μm spray-deposited aluminum doped ZnO layer. A set of fabricated devices were tested using a Keithley semiconductor characterization instrument and micromanipulator probe station. The highest measured device efficiency was 1.49%. The considered solar cell devices were simulated in ADEPT 2.0 solar cell simulator based on the given fabrication and experimental parameters. The simulation module developed was successfully calibrated with the experimental results. This module can be used for future development of the given work.
Bhat, Thirumaleshwara N. "Group III Nitride/p-Silicon Heterojunctions By Plasma Assisted Molecular Beam Epitaxy." Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2454.
Повний текст джерелаRoul, Basanta Kumar. "Group III-Nitride Epitaxial Heterostructures By Plasma-Assisted Molecular Beam Epitaxy." Thesis, 2012. http://hdl.handle.net/2005/2514.
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