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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 25 for “"free carriers"”.
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Leveraging free carriers effects for infrared photonic structures and devices
In this work, three types of novel photonic devices/structures were developed. The first one is a metal grating structure that combines the characters of ‘moth-eye’ structure and an extraordinary optical transmission grating. Therefore it has the capability to provide a uniform electrical …
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Effective masses of free carriers in lead telluride: their temperature dependence and contribution to transport properties
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering, 1962.
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The role of spatial size and orientation of electronic wavefunction in exciton dissociation at van der Waals interfaces
… Unlike typical inorganic materials in which free carriers are generated directly by the light absorption, excitons, Coulombic bound electron-hole pairs, are created upon light absorption in OPV materials. The performance of OPVs depends on how effective the bound charge transfer (CT) exciton, …
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Peculiar perovskites: Unraveling the unique optical response of hybrid organic-inorganic perovskites from first principles
… interactions between optically excited charge carriers, free-carriers, lattice vibrations, and atomic geometry influence the measured optical response of HOPs. First principles simulations provide a window to examine how these atomic-scale interactions contribute piece-by-piece to the …
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EXPERIMENTAL AND COMPUTATIONAL STUDIES OF NONLINEAR QUENCHING IN MATERIALS USED AS RADIATION DETECTORS
… excitons), and 3rd order quenching implies free carriers. A population of free carriers or bound electrons and holes has consequences beyond the difference in light yield and proportionality that result from pure 2nd or 3rd order quenching. For example, in halides with self-trapped holes, …
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Infrared absorption of neutron irradiated silicon
… samples at room temperature. Absorption due to free carriers decreased at the longer wavelengths (10-15 microns) with irradiation and cooling as was expected from past experiments. The resistivity of Si₄ increased from an assumed initial value of 10³ ohm-om to 1.89 X 10⁵ ohm-om.
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A theoretical and experimental investigation of the annular jet ground effect machine
… samples at room temperature. Absorption due to free carriers depressed at the longer wavelengths (10-15 microns) with irradiation and cooling as was expected from past experiments. The resistivity of Si₄ increased from an assumed initial value of 10³ ohm-om to 1.89 x 10⁵ ohm-om.
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Optical properties of gallium arsenide and indium gallium arsenide quantum wells and their applications to optoelectronic devices
… doped MQWS, the quenching of excitons by free carriers has been demonstrated. The comparison of the experimental results with calculations which consider phase space filling, screening, and exchange interaction showed the phase space filling to be the dominant mechanism responsible for the …
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Perovskite Light-emitting Diodes with Tunable Emission
… emitter which is crucial to confine the inherent free carriers in the material. We show that the 3D lead-halide bulk perovskite is bandgap tunable with emission in the green and red visible spectrum. Light-emitting diodes in the visible spectrum are common however near-infrared emission is a …
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Assessing electronic transport in solid materials via the fluctuation-dissipation theorem
… 𝐤-grids for the electronic degrees of freedom and large real-space supercells for the vibrational ones. This is especially challenging for the charge transport coefficient of intrinsic semiconductors with dispersive electronic structures, because the free carriers are very localised in …
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Spin and lattice properties of optically trapped exciton polaritons
… pumping. Doing so creates a large density of free- carriers and excitons that strongly interact and blueshift the polariton energy levels. Using spatially patterned nonresonant fields, the polariton potential landscape can be tailored and optically trapped condensates can be created. This …
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Absorption and emission processes in organometal trihalide perovskites
… optical excitations at room temperature are free carriers, as it happens in inorganic semiconductors. Whether photoexcitations result in bound or unbound electron-hole pairs is not a problem of minor importance, because the design of optoelectronic devices strongly depends on it. As an …
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Ab initio study of electron transport in lead telluride
… Next, we study the screening effect of free carriers on electron transport by modulating the polar scattering. These considerations enabled us to report parameter-free first-principles calculation of electron and phonon transport in PbTe, including mode-by-mode electron-phonon …
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Stabilizing Degenerate Dopants in Colloidal Semiconductor Nanocrystals
… possessing excess delocalized charge carriers are garnering considerable attention for their applications in a wide range of emerging technologies. In order to realize their incorporation into practical devices, a detailed understanding of their electronic structural properties is …
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Enhancing the Third-Order Nonlinear Optical Properties of Porphyrins and Molecular Wires
… nm (6700 cm-1) due to two-photon absorption by free carriers (electrons). Ultrafast electron relaxation was also observed. The ~100 fs lifetime of this process could reflect electron scattering in the conduction band. This DFWM method was also used to investigate the two-photon properties of …
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Optische Eigenschaften von Phasenwechselmaterialien für zukünftige optische und elektronische Speicheranwendungen
… even about electrical transport parameters. If free carrier have enough influence on the optical properties, the conductivity can be calculated. Additionally, for large Drude relaxation times, this parameter itself, the quotient of the carrier concentration and the effective mass as well as the …
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Non-metallic nanostructures for light-driven chemistry and catalysis
… by visible wavelengths of light, their free electrons undergo collective oscillations known as localized surface plasmon resonance (LSPR) oscillations. This effect has been harnessed both for harvesting visible light and for catalyzing thermodynamically uphill reactions. However, the …
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Understanding the viability of impurity-band photovoltaics : a case study of S-doped Si
… dopants, which enable the generation of free carriers using photons with energy less than that of the band gap of the host semiconductor. The investigations reported in this thesis provide a framework for the appropriate selection of impurity-band candidate materials. The thesis is …
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Sputtered tin oxide and titanium oxide thin films as alternative transparent conductive oxides
… to achieve transparent and conductive films free carriers have to be generated by oxygen vacancies, by metal ions at interstitial positions in the crystal lattice or by cation doping with Sb or Nb, respectively. Antimony doped tin oxide and niobium doped titanium oxide films have been …
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Investigation of magnetic interactions in topological insulators
… magnetic semiconductors which needs undesired free carriers to mediate the magnetism, such magnetism has an carrier-free origin and solves the dark current issue for spintronics applications, such as quantum anomalous Hall effect. Secondly, this thesis provides conclusive experimental evidence …
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