Thesis (Ph. D.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed Feb. 3, 2010). Additional advisors: Renato Camata, Derrick Dean, Chris M. Lawson, Andrei Stanishevsky, Sergey Vyazovkin. Includes bibliographical references (p. 133-140).

Rare-earth ions holmium (Ho+3), Thulium (Tm+3), and Samarium (Sm+3) were investigated for infrared emission and their possible biomedical applications by a photoluminescence (PL) system. Holmium’s (Ho+3) emission peaks were the result of transitions 5 S2 → 5 I7, and 5 S2 → 5 I5 respectively. Samarium’s (Sm+3) emission peaks were 936 nm and 1863 nm. Thulium’s (Tm+3) emission peaks were the a result of transitions 3 H4 → 3 H6, 3 H5 → 3 H6 , and 3 F4 → 3 H6 respectively. Erbium Oxide nanoparticles (Er2O3) mixed with water by a photoluminescence (PL) system. Erbium Oxide’ (Er2O3) nanoparticle’s emission peaks were the a result of transitions 4 I15/2 → 4 S3/2 , 4 I15/2 → 4 I13/2 respectively. The process was also repeated in vacuum and it was found that the green emission enhances tremendously when the nanoparticles are excited in vacuum. This enhanced luminescence from the Erbium Oxide nanoparticles shows their potential importance in the optical devices and Biomedical applications. / Department of Physics and Astronomy

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (p. [225]-236).

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 114-127).

Layered transition metal dichalcogenides (TMDs) are potentially ideal semiconducting materials due to their in-plane carrier transport and tunable bandgaps, which are favorable properties for electrical and optoelectronic applications. However, the ability to make p-n junctions is the foundation of semiconductor devices, and therefore the ability to achieve reproducible p- and n-type doping in TMD semiconducting materials is critical. In this work, p-type substitutional doping of pulsed laser deposited WS2 films with niobium is reported. The synthesis technique of the PLD target with dopant incorporation which also ensures host material stoichiometry is presented. Hall electrical measurements confirmed stable p-type conductivity of the grown films. Structural characterization revealed that there was no segregation phase of niobium in the fabricated films and x-ray phtoelectron spectroscopy (xps) characterization suggest that the p-type doping is due to Nb4+ which results in p-type behavior. Stable hole concentrations as high as 10E21(cm-3) were achieved. The target fabrication and thin film deposition technique reported here can be used for substitutional doping of other 2D materials to obtain stable doping for device applications.

Dans cette thèse nous considérons un semi-conducteur de GaAs dopé, où nous étudions la relaxation du spin du côté métallique de la transition metal-isolant. Nous considérons deux types différents d'interaction de spin-orbite. Le premier d'entre eux est associé aux impuretés et l'autre est de type Dresselhaus. La dynamique du spin est traitée à travers une formulation analytique basée sur la diffusion du spin de l'électron, et un calcul numérique de la durée de vie du spin.Ensuite, nous considérons une boîte quantique hébergée dans un nanofil de matériau InAs (avec une structure cristalline de type wurtzite), afin d'étudier l'effet de l'interaction spin-orbite sur les états propres du système. Nous développons ici une solution analytique pour la boîte quantique en incluant l'interaction spin-orbite (de type Dresselhaus propre à la structure wurtzite). Nous avons calculé le facteur g effectif, ainsi que la relaxation du spin dûe aux phonons acoustiques, en utilisant les potentiels d'interaction electron-phonon propres à la structure wurtzite. / In the first part of this thesis we consider a doped GaAs semiconductor and study the spin relaxation on the metallic side of the metal-insulator transition. We take into account two different types of spinorbit coupling, the first of them being associated to the presence of extrinsic impurities, while the other one is the Dresselhaus coupling. To tackle the spin dynamics problem, we develop an analytical formulation based on the spin diffusion of an electron in the metallic regime of conduction of the impurity band. The full derivation provides us with an expression for the spin-relaxation time ,which is free of adjustable parameters. We complement this approach and back our analytical results with the numerical calculation of the spin lifetime.In the second part of the thesis we consider a quantum dot hosted in an InAs nanowire (with awurtzite crystalline structure) and study the effect of spin-orbit coupling on the eigenstates of the zero-dimensional system. We develop here an exact analytical solution for the quantum dot, takinginto account the proper effective spin-orbit coupling for this type of material. We focus on the Dresselhaus coupling, which presents a cubic-in-k term, along with a linear term, characteristic of wurtzite materials. A Zeeman interaction from an external magnetic field is included as well and we compute the effective g-factor as a function of the dot size. Finally, we calculate the spin-relaxation due to acoustic phonons, taking into account the phonon potentials corresponding to the wurtzite structure.

Le contrôle des ondes électromagnétiques joue un rôle fondamental dans les technologies photoniques actuelles. De nos jours, on assiste à une demande croissante de composants agiles capable d'absorber efficacement les ondes électromagnétiques dans divers gamme de fréquences. Habituellement, ces absorbeurs s'appuient sur les résonances plasmoniques qui apparaissent dans les métaux nobles dans la gamme visible. Cependant, l'extension des propriétés plasmoniques aux spectres infrarouge et THz nécessite des matériaux adéquats ayant un comportement métallique à ces fréquences. Dans ce travail, nous étudions numériquement et expérimentalement les structures métal-isolant-métal (MIM) réalisées à partir de semi-conducteur hautement dopé Si: InAsSb qui a un comportement métallique dans la gamme infrarouge. Dans la deuxième partie, nous avons amélioré l'efficacité des résonateurs MIM en utilisant des métamatériaux hyperboliques qui miniaturisent les résonateurs. Dans la dernière partie, nous proposons un design universel ultra-mince qui permet de dépasser les contraintes associées au choix des matériaux et permettant la réalisation d'un absorbeur fonctionnant sur une gamme spectrale allant de l'infrarouge aux micro-onde. / The control of light absorbance plays a fundamental role in today's photonic technologies. And the urge to design and develop flexible structures that can absorb electromagnetic waves is very growing these days. Usually, these absorbers relies on plasmonic resonances that arise in noble metals in the visible range. However, the extension of the plasmonic properties to the infrared and THz spectra requires adequate materials that have a metallic behavior at these frequencies. In this work, we study numerically and experimentally the metal-insulator-metal (MIM) structures realized from highly doped semiconductor Si:InAsSb that has a metallic behavior in the infrared range. In the second, part we improved the efficiency of the MIM resonators by using hyperbolic metamaterials that also miniaturize the resonators. In the last part, we propose an ultra-thin universal design that overcomes the material barrier so that the total absorption can be achieved for different spectral ranges without changing the material.

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