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 18 of 18 for “"energy shifts"”.
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Coherent light-matter interactions in monolayer transition-metal dichalcogenides
… these valleys are normally locked in the same energy level, which limits their potential use for applications. This dissertation presents the optical methods to split their energy levels by means of coherent light-matter interactions. Experiments were performed in a pump-probe technique using a …
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Photoemission and scanning tunneling microscopy investigation of elemental-semiconductor surfaces
… and in inequivalent sites by their binding energy shifts. By comparison with structural models and reference samples the number of atoms in each distinct chemical configuration can be determined. An adsorbate-induced chemical shift can be correlated with electronegativity differences between …
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Exciton transport and thermodynamics in gallium arsenide quantum wells
… in understanding the spatial transport and energy relaxation of excitons in quantum well systems. I discuss the mechanism of carrier-induced changes in the absorption spectrum of a 210A GaAs multiple quantum well, and show that at moderate densities, the enhanced transmission at the …
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Pressure Tuning Spectroscopy of Metal Cluster Compounds and Organometallics
… affords the opportunity to measure the relative energy shifts of two occupied bonding electronic levels (as well as two unoccupied antibonding levels; (2) pressure can serve to cause a torsional isomerization in binuclear metal cluster compounds, even when the two metal atoms are bonded to …
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Characterization of Local field effect in organic film using pressure technique
… of local dielectric changes on the excitonic energy levels in amorphous organic thin films for optoelectronic device applications. Compression of organic films causes a decrease in intermolecular spacing and, through solvation effects, lowers the exciton transition energy. A series of …
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Operando Characterization of Lithium-Ion Batteries using Lab-Scale X-ray Emission/Absorption Spectroscopy
… as they are more accessible and provide energy resolution close to that of a synchrotron source. In this study, the use of a lab-scale XAFS/XES to investigate the change in the electronic structure around transition elements present in electrode materials for lithium-ion storage is …
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Untangling energy dependent radiation damping and chemical interface damping in gold nanorods
… these terms can become entangled due to large energy shifts induced by metal oxide coatings that provide acceptor states for interfacial charge transfer. Additionally, the size of plasmonic nanoparticles plays a critical role in altering the contribution ratio of radiation damping and chemical …
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Photoemission and scanning tunneling microscopy investigation of elemental-semiconductor surfaces
… and in inequivalent sites by their binding energy shifts. By comparison with structural models and reference samples the number of atoms in each distinct chemical configuration can be determined. An adsorbate-induced chemical shift can be correlated with electronegativity differences between …
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The Mossbauer effect of FE57 on the surface of tungsten
The Mossbuaer effect of Fe 57 on the surface of polycrystalline tungsten has been measured over a temperature range of 80 - 5000 K, and at angles of 0° and 60° with respect to the normal. The M8ssbauer spectra consist of three unresolved lines, the middle one agreeing with measured spectra of Fe 57 …
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Energy level engineering in colloidal quantum dot solar cells
… In this thesis we demonstrate how control of the energy level profile within PbS QD solar cells can be used to understand and improve their operation. First, we demonstrate that improvements in power conversion efficiency may be attained for ZnO / PbS QD heterojunction photovoltaics through the …
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Correlated exciton dynamics in semiconductor nanostructures
The absorption and dissipation of energy in semiconductor nanostructures are often determined by excited electron dynamics. In semiconductors, one fundamentally important electronic state is an exciton, an excited electron bound to a positively charged vacancy. Excitons can become correlated with …
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Investigation of new semiconductor materials for wide band-gap devices
… agreement with the near-band edge (NBE) emission energy and the material bandgap expected from the alloy concentration for all AlxGa1−xN crystal orientations. Compared to polar AlxGa1−xN NBE emission showed a high degree of broadening with increasing AlN content due to compositional variation in …
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Luminescence of impurity-activated alkali halides under high pressure
… with higher pressure favoring the higher energy A.r emission, known to occur from an excited state of tetragonal symmetry. In the high pressure CsCI-phase, a similar emission doublet was observed in both In+-and TI+-doped potassium and cesium halides. Again, pressure causes a …
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Understanding electronic and optical properties of PbS QDs for improved photovoltaic performance
… and metallic electrical contacts convert solar energy to electricity. Even though silicon represents roughly 90% of installed solar PV capacity as the clear current leader among PV technology, another class of solid-state solar cells, referred to as quantum dot (QD) solar cells, have gained much …
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Photoionization and excitation of free variable size van der Waals clusters in the inner shell regime
… clusters are performed by using zero kinetic energy (ZEKE) photoelectron spectroscopy in the Ar 2p-, Kr 3d-, Ne 1s-, and N2-regimes. The experimental approach is also suitable to detect cluster size dependent changes in electronic structure. This also allows us to study post collision …
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A new apparatus to simulate fundamental interactions with ultracold atoms
… of different components. Due to the peculiar energy dependence of such a configuration, an attractive force, independent of the vortex distance, is expected, making this system a candidate for mimicking features of quark confinement in QCD. The surface tension of the domain wall structure can …
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Dinamica effettiva di sistemi quantistici driven chiusi e aperti
… terms determine the usual Bloch-Siegert shifts off-resonance (besides the Stark shift due to the corotating field), while giving at resonance, besides the Bloch-Siegert, a renormalization of the amplitude of the corotating field. As a final application of coarse graining by the Magnus …
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Characterization of bio-hybrid interfaces under ambient conditions
… molecules. Atomic force microscopy (AFM), low energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS) in ultra-high vacuum (UHV) and near-ambient-pressure (NAP) conditions were used for this investigation. Monochromatic X-ray 𝐴𝐴𝐴𝐴 𝐾𝐾𝐾𝐾 radi ation (ℎ𝜋𝜋 = 1486.7𝑒𝑒𝑉𝑉) was …