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 22 for “"Localized states"”.
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Probing localized states distributions in semiconductors by Laplace transform transient photocurrent spectroscopy
… and a definition of the density of electronic states (DOS) is given. The DOS will be referred to frequently in this work. Also charge transport and photoconductivity in amorphous semiconductors are briefly described.<br/><br/>In chapter I the Multiple Trapping model (MT), widely used to …
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Relaxation of interacting Stark-localized states in a thermal lattice Bose gas
Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2023-12-04 without embargo terms
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First-Principles Study of Electronic Structure and Optical Properties of Semiconductor Surfaces Unified Approach for Exact Calculation of Coupling Coefficients of Quantum Angular Momenta
… results for the dynamics of an initially localized two-level (TLS) system coupled to a generic dissipative environment and driven by a periodic force which in the semiclassical limit is equivalent to a continuous-wave electromagnetic field. The time evolution is calculated via iterative …
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Localization properties of nonlinear disordered lattices
… In Part II, the spreading behavior of initially localized states in large, disordered chains due to nonlinearity is studied. Therefore, different methods to measure localization are discussed and the structural entropy as a measure for the peak structure of probability distributions is …
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Superconductivity in Multi-Band and Disordered Systems
… the Mott gap through the generation of mid-gap localized states at the chemical potential. Depending on the magnitude of the disorder, we find that the destruction of the Mott state takes place for d + z > 4 either through a Bose glass phase (strong disorder) or through a direct transition to a …
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Thermoelectric characterization of one- and two- dimensional materials
… electron transport is heavily influenced by the localized states formed in their band gaps. By fitting the experimentally obtained temperature and gate voltage dependence of S and σ with a theoretical model, a determination of the nature of the localized states and the electron transport …
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Anderson Localization in Low-Dimensional Systems with Long-Range Correlated Disorder
… invariance of the system, the electronic eigenstates will localize in space. This phenomenon is called Anderson localization after Phillip Anderson who first predicted it in 1958. Since then, Anderson localization has remained a vibrant topic of research due to new experimental methods of …
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Silicon rich nitride for silicon based laser devices
… optical confinement. Strong light emission from localized states in Si-nc embedded in SRN was demonstrated with a PLQE (Photoluminescence Quantum Efficiency) of 7%. This effect was confirmed through several experiments and first principle calculations. Thue Morse aperiodic structures were …
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Probing and preparing novel states of quantum degenerate rubidium atoms in optical lattices
… this goal, as important as engineering new states of matter is the need to develop new techniques to probe these systems. I first describe our work on realizing Bragg scattering of infrared light from ultracold atoms in optical lattices. This is a detection technique which probes the spatial …
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Characteristics of nanocomposites and semiconductor heterostructure wafers using THz spectroscopy
… suggest that the photoexcited nanotubes exhibit localized transport due to Lorentz-type photo-induced localized states from 0.2 to 0.7THz. The THz transmission is modeled through the photoexcited layer with an effective dielectric constant described by a Drude + Lorentz model and given by …
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Homoclinic snaking in discrete systems
… analytically and numerically bifurcations of localized solutions in discrete systems, i.e., the discrete Swift-Hohenberg, an optical cavity equation, and the discrete Allen-Cahn equation, which have infinitely multiplicity called homoclinic snaking. First, we study the discrete Swift-Hohenberg …
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Atomic-scale assessment of graphene-substrate interactions, grain boundaries, and materials for heterostructures
… local graphene electronic structure, leading to localized states and decreased the local work functions. The GBs induce p-n-p and p-p’-p (p’ < p) potential barriers that scatter charge carriers. This effect occurs over a length scale of ~1 – 2 nm on either side of the GBs. We employ the ultrahigh …
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Spectroscopic Studies of Excited States in Carbene-Metal-Amide Emitters
… substitutions, we show that energies of multiple states can be simultaneously shifted. We find that these shifts can be qualitatively rationalized from a perturbation theory approach, resulting in a design principle for blueshifting emission while avoiding donor-localized states previously linked …
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Tunneling spectroscopy of the two-dimensional electron gas
We measure the single particle density of states (DOS) of a two-dimensional electron system (2DES) in a GaAs/AlGaAs heterostructure. Using a technique that we call "Time Domain Capacitance Spectroscopy" (TDCS), we measure the complete current-voltage characteristics for tunneling into the 2DES …
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Effects of isotope doping on the phonon modes in graphene
… some graphene phonon wave-functions become localized in real space. Numerical calculations show that phonon localized states exist in the high-energy optical phonon modes and in regions of flat phonon dispersion. In particular, for the case of in-plane optical phonon modes, a typical …
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Synthesis and thermoelectric properties of Mg2Si-Mg2Sn solid solutions for waste heat recovery
… The results suggest that Mg vacancies create localized hole states inside the band gap instead of moving the Fermi level into the valence band as would be predicted by a rigid band model. This hypothesis is confirmed by density-functional theory calculations, which show that the hole states …
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Charge detection in semiconductor nanostructures
… charge detection. We extract the density of localized states at the Fermi level for the a-Si:H and obtain consistent results. We discuss the effect of screening by the substrate on the sensitivity of the MOSFET to charge in the a-Si:H, and show that the MOSFET can detect switching noise in …
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Development of large scale tight-binding methods, and application to electron transfer in symmetric dielectric barrier discharges (DBDS)
… model, where electron transfer occurs between localized states due to time-dependent resonance. We first show that the temporal profile of current-voltage obtained from this model are consistent with experimental observations, and then go on to numerically compute the rates of electron transfer …
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Charge and Thermoelectric Transport in Semicrystalline Conjugated Polymers and Single-Walled Carbon Nanotube Networks
… into the transport energetics and the density of states (DoS). It can be used to identify the prevailing transport mechanisms, such as phonon-assisted hopping between localized states or scattering-limited transport through delocalized states, scattering mechanisms and carrier-carrier interactions …
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Redox properties of Bis-Triarylamines and ligand properties of Thianthrenophane
… of the corresponding X-B monomers. The excited states of the dimers are described as MV states which show, depending on the chemical nature of the bridge, a varying amount of interactions. It was found that superradiant emission only proceeds in the case of weak and medium coupling. Whether the …
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