Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 54 for “"defect states"”.
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Modelling of defect states in covalent amorphous solids
… molecular dynamics simulations, of the bulk and defect structures, in hydrogenated amorphous silicon. Emphasis is given to the systematic analysis of the changes in the network structures, which occur due to the incorporation of hydrogen, at different levels of concentration. The atomic-level …
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Optically induced metastable defect states in amorphous silicon dioxide
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1986.
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Redefining the Operation and Design Considerations of Organic Solar Cells: Role of Morphology and Defect States
… on the role of active layer morphology and defect states in organic semiconducting devices, which will broaden the field of organic electronics.</p>
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Understanding defects in germanium and silicon for optoelectronic energy conversion
This thesis explores bulk and interface defects in germanium (Ge) and silicon (Si) with a focus on understanding the impact defect related bandgap states will have on optoelectronic applications. Optoelectronic devices are minority carrier devices and are particularly sensitive to defect states …
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Broad Band Excitation of Rare-Earth Dopants in Chalcogenide Glasses
… of energy to the rare earth dopants, mediated by defect states in the glass. Studies on the effect of changing the rare earth dopant, the host glass bandgap, the host glass composition, and the sample temperature have all been performed. From numerous similarities to the host glass PLE lineshape, …
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Broad excitation of rare earth dopants in chalcogenide glasses
… of energy to the rare earth dopants, mediated by defect states in the glass. Studies on the effect of changing the rare earth dopant, the host glass bandgap, the host glass composition, and the sample temperature have all been performed. From numerous similarities to the host glass PLE lineshape, …
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Defect spectroscopy on Cu(In,Ga)(S,Se) 2 -based heterojunction solar cells: role of the damp-heat treatment
The changes of defect characteristics induced by accelerated lifetime tests on solar cells of the heterostructure ZnO/CdS/Cu(In,Ga)(S,Se)2/Mo are investigated. The fill factor and open-circuit voltage of non-encapsulated test cells are reduced after prolonged damp-heat treatment in the laboratory, …
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Non-Hermitian topological states in photonic systems
… far the current classification of topological states extends. This work invigorates the search for topological states in photonic systems with the hope of describing new mechanisms for controlling and increasing the number of physical systems in which robust light transport can be achieved. In …
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Multi-pulse nonlinear optical spectroscopy and light-matter interactions in layered materials.
… in the visible regime. However, the presence of defect states within the crystal structure can affect these properties, resulting in changes to their emission and the emergence of nonlinear optical phenomena. Here, we have investigated the effects of the presence of defect states on the nonlinear …
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Growth and properties of hydrogenated amorphous silicon carbon alloys by DC reactive magnetron sputtering
… excellent in terms of density of sub-bandgap defect states DOS, Urbach energy E$\rm\sb{U},$ ambipolar diffusion length L$\rm\sb{h},$ photoconductive mobility-lifetime product $\mu\tau$ and dark conductivity $\rm\sigma\sb{D}$ for Tauc bandgap E$\rm\sb{g}\approx$ 1.90 eV. We attribute the …
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Optical studies of photonic crystals and high index-contrast microphotonic circuits
… In addition, nano-scale photonic crystal defect modes are studied over large optical bandwidths through newly developed supercontinuum based techniques. Novel all-fiber supercontinuum sources facilitate the generation of unpolarized supercontinuum light over 1.2-2.0 micron wavelengths. …
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Study of deep level defects of N+-CdS/P-CdTe solar cells
… cells. There is no real distinction between defects and impurities in CdTe solar cells as both act as beneficial dopants or detrimental traps unlike Si where intentional shallow dopants and traps are distinctly different. Therefore, the role of defect states on CdTe solar cell performance, …
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Plasmon supported defect absorption in amorphous silicon thin film solar cells and devices
… for photon energies below the bandgap of a-Si:H. States must be present that allow transitions for sub-bandgap energies. By a variation of the Ag NP position within the applied devices the role of interface states is evaluated. It turns out that defects in the a-Si:H material are responsible, that …
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Density Functional Simulations of Defect Behavior in Oxides for Applications in MOSFET and Resistive Memory
Defects in the functional oxides play an important role in electronic devices like metal oxide semiconductor field effect transistors (MOSFETs) and resistive random-access memories (ReRAMs). The continuous scaling of CMOS has brought the Si MOSFET to its physical technology limit and the …
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Phase-and-Defect Diagrams for Polycrystalline Grain Boundary Segregation
Defect engineering provides access to a much larger range of material properties and is particularly necessary when designing any high-defect density material such as nanocrystalline (NC) alloys. Traditionally, bulk equilibrium phases have been considered in a decoupled manner from defects, such as …
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Novel characterization of materials using THz spectroscopic techniques
… of this work has been to deduce the number of defect states in buried layers. The study also attempts to develop a preliminary model based on effective medium approximations to predict the thickness of the interfacial layer which might be having a myriad of applications in the semiconductor …
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Synthesis of functionalized few layer graphene via electrochemical expansion
… oxidation of graphene and the associated defect generation encountered with the broadly used Hummer's method. The expansion and charging of the graphite by intercalation of cations facilitates the functionalization of the graphene basal surfaces. Electrochemically enhanced diazonium …
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Fluctuations in dc SQUIDs: Quantum Noise Effects, Low Frequency Noise, and Single Electron Trapping
… untrapping of single electrons into localized defect states residing within the tunneling barrier. The weak temperature of the trap lifetimes reveals that the trapping process displays tunneling kinetics. In contrast, the voltage bias dependence of the lifetimes is consistent with a simple …
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XPS and transport studies of oxide barriers in tunnel magnetoresistance junctions
… of inelastic tunneling via chains of localized defect states in the tunnel barrier. The Glazmann-Matveev model enables the separation of the elastic and the inelastic components of the tunnel conductivity at different temperatures and bias voltages.
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Electronic States near Surfaces - a) Analysis of calculation methods using semi-infinite boundary conditions; b) Sensitive detection using laser photoelectron spectroscopy
… a low-background, sensitive view of electronic states in the band gap and photo-populated states above the Fermi level. Measurements of photoelectron emission for ultra-high vacuum cleaved surfaces of CdSe, excited by 4.5 and 5.9 eV Ti:sapphire laser pulses of 150 femtosecond duration are …
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