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Dissertations / Theses on the topic 'Solid-state electronics structures'

Author: Grafiati

Published: 28 May 2022

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1

Guerreiro, Paulo Tiago Ferraz de Meira 1967. "Solid-state laser mode-locking and ultrafast studies in quantum semiconductor structures." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282515.

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This dissertation describes the development of ultra-short pulse solid-state lasers and the investigation of ultra-short pulse propagation in a nonlinear waveguide. We present laser design considerations involving astigmatism compensation, spot-size estimation, stability, and dispersion compensation, and their application to chromium doped forsterite lasers. Making use of the Kerr nonlinearity of the Cr:forsterite crystal we demonstrate self-mode-locking in Cr:forsterite lasers, both in the hard-aperture and soft-aperture Kerr-lens mode-locking regimes. Sub-200-fs pulses tunable between 1240 and 1285 nm were obtained, with the shortest transform-limited pulses having 45 fs duration at 90 MHz repetition rate with 100 mW output power at 1265 nm. Using a semiconductor quantum-well saturable absorber integrated with a Bragg reflector we demonstrated self-starting passive continuous-wave mode-locked operation of a Cr:forsterite laser. Self-starting mode-locking was the only operational mode of the laser and could be achieved with and without intracavity dispersion compensation. We obtained 70 fs transformed-limited pulses using a prism pair for dispersion compensation, 4 ps pulses without prisms, and pulse energies of up to 2.3 nJ at 90 MHz repetition rate at 1260 nm. Using quantum-confined nanocrystals of lead sulfide in glass as intracavity saturable absorbers we obtained self-starting passive continuous-wave mode-locking in a Cr:forsterite laser. We obtained near transform-limited 4.6 ps laser pulses at 100 MHz repetition rate, and a wide tunability range of 1207 to 1307 nm. We studied femtosecond pulse propagation near a two-photon transition in CdS quantum-dot-doped waveguides produced by the solgel and ion-exchange methods. The observed two-photon absorption and asymmetric spectral modulation of the transmitted pulses were explained by the theoretical model, which incorporated a near-resonant two-photon transition.

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2

Zhang, Shuo. "Analysis of Phase Transitions and Crystal Structures of Novel Benzothiophene Derivatives." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1449831649.

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3

Jones, R. E. "Electronic processes in electroluminescent device structures." Thesis, Durham University, 1986. http://etheses.dur.ac.uk/7031/.

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Electronic processes in two different electroluminescent device structures, the forward biassed metal/thick insulator/semiconductor (MIS) diode and the high field metal/insulator/metal (MIM) panel, are investigated. Models are produced to explain the behaviour of two particular MIS systems which have been studied experimentally. One of these systems is the Au/cadmium stearate/n-GaP structure, where the insulator is deposited using Langmuir-Blodgett (LB) technology. The other is the Au/i-ZnS/n-ZnS structure. In the MIS devices electroluminescence occurs as a result of the recombination of electrons and holes in the semiconductor and so it is necessary to have an efficient minority carrier (hole) injection mechanism. Attention is paid to the impact excitation of the electron gas in the metal by the electrons injected from the semiconductor because this has been proposed by other workers as a process for producing holes in the metal that are energetically capable of entering the semiconductor valence band, provided they can traverse the insulator. The characteristics of the LB film devices are found to be best described by assuming the minority carrier injection to be limited by the hole transport through the insulator. Hopping between interface states on the successive LB layers is proposed as the transport mechanism. However, the device incorporating a II-VI semi-insulator is shown to be more characteristic of hole transport in the insulator valence band and a minority carrier injection which is limited by the supply of holes from the metal. In high field MIM panels the mechanism of electroluminescence is quite different with impurity centres being impact excited or impact ionised by injected electrons and subsequently luminescing. Such devices driven by a dc signal are susceptible to the formation of high current filaments which burn out and result in device failure. A model is developed which predicts that there is a voltage range over which the device can exist in either a low current state or two higher current states and the resultant instability is expected to be destructive. Current-voltage characteristics are produced using this model and their general features are found to be relatively insensitive to material and device parameters. In order to understand the evolution of the electrical state of the MIM device after switch-on, a time dependent theory of system behaviour is also developed. This is particularly important as the devices are usually driven by a pulsed signal. For an homogeneous system the current is found to converge to the lower current state of the steady state characteristic.

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4

Formstone, Carl. "Electronic structure of intercalation compounds." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276842.

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5

Moody, Aidan G. "The electronic structure of diazabutadiene complexes." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389183.

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6

Bush, Ian J. "The electronic structure of disordered materials." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334224.

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7

Charlesworth, Jason. "Electronic structure of metal-semiconductor interfaces." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239738.

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8

Oloumi, Mahmoud. "Electronic structure and band offsets in semiconductor heterostructures." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314685.

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9

Birkett, M. J. "Opto-electronic studies of semiconductor tunnelling structures and quantum wells." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267179.

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10

Zianni, X. "Electrons and phonons in low-dimensional semiconductor structures." Thesis, University of Warwick, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387393.

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11

Blyth, Robert I. R. "Bulk and surface electronic structure of rare earth metals." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316767.

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The basic properties of the rare earth metals, including single crystal growth, crystal and magnetic structures, and the relationship between electronic and magnetic structure, are reviewed. The problems encountered by the theoretical treatment of the partially occupied, but highly localised, lanthanide 4f levels as bands are discussed, and bandstructure calculations presented for the hexagonal close-packed rare earths. These are compared with available experimental and theoretical data. It is suggested that the exchange-splitting of the lanthanide valence bands may well persist in the paramagnetic state, and that account should be taken of the localised 4f moments in future calculations. The difficulties associated with the preparation of clean single crystal rare earth surfaces are described. The origin of the surface-orderdependent state seen in angle-resolved UV photoemission (ARUPS) spectra from rare earth (0/001) surfaces is discussed. (7 x 1) reconstructions of the (1120) surfaces of Ho, Er and Y are reported, with the resulting surface geometric and electronic structure being indistinguishable from those of the ideal (0001) structure. Momentum-resolved inverse photoernission measurements are presented for Y(000l), with results in good agreement with the calculated bandstructure. A comprehensive ARUPS study of the valence band of Ho(OOOl) is reported, and the results demonstrated to be entirely explicable in terms of emission from one-electron states. ARUPS data from Y(000l), Gd(000l) and Tb(000l) are presented, discussed in the light of the Ho results, and the conclusions of previous ARUPS studies of these surfaces revealed to be in error. Essentially similar ARUPS features are seen on all hcp rare earth (0001) surfaces so far studied and it is suggested that all other such surfaces will show the same features. The Ho(000l) 5p levels are shown to have significant band character, suggesting that further refinements to the band structure calculations are required.

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12

Bass, Julian M. "Electronic structure and band offsets of silicon-germanium superlattices." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316322.

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13

Brooks, Neal John. "The electronic and physical structure of copper palladium alloys." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320609.

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14

Fowles, Paul Stephen. "The electronic structure of metals studied by Auger spectroscopy." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279693.

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15

Ogborne, Darren Michael. "The structure and electronic properties of thallium-based superconductors." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239651.

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16

Kervern, Gwendal. "High-resolution solid-state NMR of paramagnetic molecules." Lyon, École normale supérieure (sciences), 2008. http://www.theses.fr/2008ENSL0483.

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Cette thèse porte sur la RMN haute résolution de composés paramagnétiques solides. Elle présente de nouvelles méthodes permettant d'obtenir de tels spectres, ainsi que l'exploitation des spectres ainsi obtenus pour la caractérisation structurale de complexes paramagnétiques. Nous avons dans un premier temps développé des méthodes qui permettent de surmonter les difficultés liées au paramagnétisme. Ces méthodes inclues du transfert d'aimantation par recouplage dipolaire, l'adaptation d'impulsions adiabatiques pour les solides en rotation à très haute vitesse et la compréhension des phénomènes mis en cause dans leur efficacité. Nous présentons ensuite l'exploitation des données ainsi obtenues. Notamment pour la caractérisation de la structure électronique d'un catalyseur à base de fer à haut spin, la démonstration de l'absence de relaxation dite "de Curie" dans les solides ainsi que le développement d'un nouvel outil de cristallographie par RMN de poudres
This thesis is about high-resolution solid-state NMR of paramagnetic molecules. It exposes new methods to obtain high-resolution NMR spectra of paramagnetic solids. These methods gave us access to the structural information born by the electronic paramagnetism. In the first part, we propose new tools to overcome the difficulties associated with NMR of paramagnetic solids. These methods include proton to carbon magnetization transfer via dipolar recoupling, the use of adiabatic pulses with paramagnetic solids rotating at high MAS speeds, the development of a theory for a better understanding of the physics of such pulses. The second part exposes the interpretation of the high quality spectra obtained throught those methods. We characterized the electronic structure of high-spin iron (II) catalyst, we tackled the absence of the so-called "Curie relaxation" mechanism in the solid-state an we developed a new tool for crystallography thanks to proton NMR of paramagnetic powedrs

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17

Dou, Yusheng. "The electronic structure of cadmium oxides studied by photoemission spectroscopy." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389218.

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18

Pigram, David Dennis. "The electronic structure of the ferromagnets cobalt and cobalt disulphide." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306516.

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19

Lague, Stephen Brian. "The structural and electronic properties of some liquid semiconductors." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336931.

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20

Warren, Rachel Frances. "Optical, electronic and structural properties of metal halide intercalates." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333365.

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21

Wright, Helen Elizabeth. "Studies of the electronic structure of metals and alloys by electron spectroscopy." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329397.

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22

Newell, Mark Alistair. "Physical and electronic structure of simple metal systems studied by electron spectroscopy." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333499.

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23

Lee, Myoung Ho. "Electronic and structure studies of Gd/W and Y/W thin films." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264277.

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24

Hall, David Oakley. "Calculations of the electronic structure and optical properties of strained II-VI superlattices." Thesis, Durham University, 1991. http://etheses.dur.ac.uk/1549/.

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25

Vettese, Carlo Ettore. "The effects of multi-quantum well inter-mixing on long-wavelength opto-electronic structures and devices." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387226.

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26

Dugdale, Stephen Brian. "A new approach to positron annihilation fermiology : the electronic structure of chromium, yttrium and gadolinium." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319141.

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27

Erslev, Peter Tweedie 1979. "The electronic structure within the mobility gap of transparent amorphous oxide semiconductors." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/10566.

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xix, 142 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
Transparent amorphous oxide semiconductors are a relatively new class of materials which show significant promise for electronic device applications. The electron mobility in these materials is at least ten times greater than that of the current dominant material for thin-film transistors: amorphous silicon. The density of states within the gap of a semiconductor largely determines the characteristics of a device fabricated from it. Thus, a fundamental understanding of the electronic structure within the mobility gap of amorphous oxides is crucial to fully developing technologies based around them. Amorphous zinc tin oxide (ZTO) and indium gallium zinc oxide (IGZO) were investigated in order to determine this sub-gap structure. Junction-capacitance based methods including admittance spectroscopy and drive level capacitance profiling (DLCP) were used to find the free carrier and deep defect densities. Defects located near insulator-semiconductor interfaces were commonly observed and strongly depended on fabrication conditions. Transient photocapacitance spectroscopy (TPC) indicated broad valence band-tails for both the ZTO and IGZO samples, characterized by Urbach energies of 110±20 meV. These large band-tail widths imply that significant structural disorder exists in the atomic lattice of these materials. While such broad band-tails generally correlate with poor electronic transport properties, the density of states near the conduction band is more important for devices such as transistors. The TPC spectra also revealed an optically active defect located at the insulator-semiconductor junction. Space-charge-limited current (SCLC) measurements were attempted in order to deduce the density of states near the conduction band. While the SCLC results were promising, their interpretation was too ambiguous to obtain a detailed picture of the electronic state distribution. Another technique, modulated photocurrent spectroscopy (MPC), was then employed for this purpose. Using this method narrow conduction band-tails were determined for the ZTO samples with Urbach energies near 10 meV. Thus, by combining the results of the DLCP, TPC and MPC measurements, a quite complete picture of the density of states within the mobility gap of these amorphous oxides has emerged. The relationship of this state distribution to transistor performance is discussed as well as to the future development of device applications of these materials.
Committee in charge: Stephen Kevan, Chairperson, Physics; J David Cohen, Member, Physics; David Strom, Member, Physics; Jens Noeckel, Member, Physics; David Johnson, Outside Member, Chemistry

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28

Merveille, Christiaan. "Nanosecond-scale nonlinear-optical properties of electronic origin of ZnSe and of ZnSe(Zn,Cd)Se MQW-structures." Thesis, Heriot-Watt University, 1997. http://hdl.handle.net/10399/636.

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29

Evans, John Antony. "Studies of the local electronic structure of silicon, the arsenic - silicon(100) interface and noble metal alloys." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293735.

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30

Cole, Richard James. "The electronic structure of selected metals, alloys and interfaces studied by x-ray excited Auger and photoelectron spectroscopy." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316506.

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31

Wright, Timothy Grahame. "Studies of some gas-phase oxidation reactions using electron spectroscopy and the electronic structure of some small molecules." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358873.

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32

Niraula, Dipesh. "Physics and applications of conductive filaments in electronic structures: from metal whiskers to solid state memory." University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1561471348406944.

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33

Wong, Sun-cheung. "Ab initio calculations of silicon clusters." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20192708.

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34

Taylor, Stephen D. "Solid-state Structures and Electronic properties of Platinum(II) Terpyridyl Complexes: Implications for Vapor and Aqueous Anion Sensing." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1313772880.

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35

Zhang, Wenhua. "First Principles Studies on Chemical and Electronic Structures of Adsorbates." Doctoral thesis, KTH, Teoretisk kemi (stängd 20110512), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10215.

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In this thesis, we focus on theoretical study of adsorbates on metal and oxide surfaces that are important for surface chemistry and catalysis. Based on first principles calculations, the adsorption ofCO, NO, NO2, C4H6S2, C22H27SH and other molecules or radicals on nobel metal surfaces (gold and silver) are investigated. Also, NO oxidation on oxygen pre-covered Au(111)surface and CO oxidation on water-oxygen covered Au(111)surface aretheoretically studied. A new mechanism of water-enhanced COoxidation is proposed. As for oxide surfaces, we first investigatethe geometric, electronic and magnetic structures of FeO ultrathin film on Pt(111) surface. The experimentally observed scanning tunneling microscopy images are well reproduced for the first timewith our model. The adsorption and dissociation of water on rutileTiO2(110) surface are investigated by quantum molecular dynamics.By theoretical X-ray photoemission spectroscopy (XPS) calculations,the surface species are properly assigned. The same strategy has applied to the study of the phase transition of water covered reconstructed anatase TiO2(001) surface, from which two different phases are theoretically identified. The structure of graphene oxideis also studied by comparing experimental and theoretical XPS spectra. Based on the novel structures identified, a new cutmechanism of graphene oxide is proposed.
QC 20100819

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36

Tsutsumi, Jun'ya. "Solid-state structures and electronic properties of organic molecules fabricated by connecting electron donor and acceptor components." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/124380.

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37

黃新祥 and Sun-cheung Wong. "Ab initio calculations of silicon clusters." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B3122197X.

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38

Ball, Molly R. "First Principles Study of Electronic and Magnetic Structures in Double Perovskites." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1483702986122186.

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39

Cui, Dongtao. "¹⁵N SOLID-STATE NMR DETECTION OF FLAVIN PERTURBATION BY H-BONDING IN MODELS AND ENZYME ACTIVE SITES." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/48.

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Massey and Hemmerich proposed that the different reactivities displayed by different flavoenzymes could be achieved as a result of dominance of different flavin ring resonance structures in different binding sites. Thus, the FMN cofactor would engage in different reactions when it had different electronic structures. To test this proposal and understand how different protein sites could produce different flavin electronic structures, we are developing solid-state NMR as a means of characterizing the electronic state of the flavin ring, via the 15N chemical shift tensors of the ring N atoms. These provide information on the frontier orbitals. We propose that the 15N chemical shift tensors of flavins engaged in different hydrogen bonds will differ from one another. Tetraphenylacetyl riboflavin (TPARF) is soluble in benzene to over 250 mM, so, this flavin alone and in complexes with binding partners provides a system for studying the effects of formation of specific hydrogen bonds. For N5, the redoxactive N atom, one of the chemical shift principle values (CSPVs) changed 10 ppm upon formation of a hydrogen bonded complex, and the results could be replicated computationally. Thus our DFT-derived frontier orbitals are validated by spectroscopy and can be used to understand reactivity. Indeed, our calculations indicate that the electron density in the diazabutadiene system diminishes upon H-bond complex formation, consistent with the observed 100 mV increase in reduction midpoint potential. Thus, the current studies of TPARF and its complexes provide a useful baseline for further SSNMR studies aimed at understanding flavin reactivity in enzymes.

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40

King, Graham Missell. "Structural, Magnetic, and Electronic Studies of Complex Perovskites." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1262114272.

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41

Antonis, Paul de. "The first steps in solid-state x-ray imaging : the structure and electronic properties of cadmium zinc telluride radiation detectors." Thesis, University of Surrey, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267972.

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42

Fu, Guopeng. "INVESTIGATION ON THE STRUCTURE-PROPERTY RELATIONSHIPS IN HIGHLY ION-CONDUCTIVE POLYMER ELECTROLYTE MEMBRANES FOR ALL-SOLID-STATE LITHIUM ION BATTERIES." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1508508844968127.

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43

Regoutz, Anna. "Structural and electronic properties of metal oxides." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:6f425890-b211-4b35-b438-b8de18f7ae64.

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Metal oxides are of immense technological importance. Their wide variety of structural and electronic characteristics leads to a flexibility unrivalled by other groups of materials. However, there is still much debate about the fundamental properties of some of the most widely used oxides, including TiO₂ and In₂O₃. This work presents high quality, in-depth characterisation of these two oxides in pure and doped form, including soft and hard X-ray photoelectron spectroscopy and X-ray diffraction. Bulk samples as well as thin film samples were prepared analysed. For the preparation of thin films a high quality sol-gel dip-coating method was developed, which resulted in epitaxial films. In more detail the organisation of the thesis is as follows: Chapter 1 provides an introduction to key ideas related to metal oxides and presents the metal oxides investigated in this thesis, In₂O₃, Ga₂O₃, Tl₂O₃, TiO₂, and SnO₂. Chapter 2 presents background information and Chapter 3 gives the practical details of the experimental techniques employed. Chapters 4 presents reciprocal space maps of MBE-grown In₂O₃ thin films and nanorods on YSZ substrates. Chapters 5 and 6 investigate the doping of In₂O₃ bulk samples with gallium and thallium and introduce a range of solid state characterisation techniques. Chapter 7 describes the development of a dip-coating sol-gel method for the growth of thin films of TiO₂ and shows 3D reciprocal space maps of the resulting films. Chapter 8 concerns hard x-ray photoelectron spectroscopy of undoped and Sn-doped TiO₂. Chapter 9 interconnects previous chapters by presenting 2D reciprocal space maps of nano structured epitaxial samples of In₂O₃ grown by the newly developed sol-gel based method. Chapter 10 concludes this thesis with a summary of the results.

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44

Salas-Illanes, Nora. "Electronic Structure of Selected Materials by Means of the QSGW Method within the LAPW+LO Framework." Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/19804.

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Materialien formen die moderne Welt: Sie umgeben uns in unserem alltäglichen Leben. Unser Ziel ist die Materialeigenschaften nach unseren Bedürfnissen maßzuschneidern. Viele Materialeigenschaften wie Bandücken und Elektronendichteverteilung werden durch elektronische Zustände bestimmt. Die meisten Vorhersagen in Bezug auf Materialien entstammen der Dichtefunktionaltheorie (DFT). Diese Theorie ermittelt Grundzustandseigenschaften und kann jedoch keine Energien von angeregten Zuständen liefern. Um angeregte Zusände zu beschreiben, bedarf es daher einer höherstufigen Theorie: die Vielteilchen-Störungstheorie (MBPT) . Im Rahmen von MBPT ist das üblichste Verfahren die GW-Näherung (GWA), worin Elektronen als Quasiteilchen (QP) beschrieben werden. Der Energieunterschied zwischen einem nicht-wechselwirkenden Teilchen und einem QP ist die Selbstenergie. In GWA ergibt sich die Selbsenergie als Produkt aus die Einteilchen-Greenfunktion, G, und die abgeschirmte Coulomb-Wechselwirkung, W, und führt zu der wahren Anregungsenergie von QP. Diese Doktorarbeit beinhaltet die Implementierung von selbstkonsistentem Quasiteilchen-GW (QSGW) im exciting Code. Dieses Software-Paket benutzt die Linearized-Augmented-Plane-Wave-Methode (LAPW), welche alle Elektronen gleichberechtigt behandelt. Beginnend mit DFT optimiert die QSGW-Methode den Einteilchen-Hamiltonoperator durch eine selbstkonsistente Suche eines optimierten Austausch-Korrelationspotentials. Am Ende des iterativen Prozesses liefert die QSGW-Methode Eigenfunktionen und Eigenwerte der QP. Wir präsentieren mit QSGW ermittelte elektronische Strukturen von neun kristallinen Festkörpern. Wir präsentieren die zugehörigen Bandstrukturen und Zustandsdichtediagramme und vergleichen anhand dieser die QSGW-Ergebnisse mit Ergebnissen von DFT und G0W0. Zusätzlich untersuchen wir die elektronische Ladungsdichte und Wellenfunktion in ausgewählten Materialien.
Materials shape the modern world: they appear everywhere in our daily life. We investigate what governs the material's properties, in order to tailor them to meet our needs. Properties, e.g., bandgaps, and electronic density distribution are determined by the electronic structure. Most predictions on materials follow from computational physics, in particular density-functional theory (DFT). This scheme returns ground-state properties, but it fails to provide excited-state energies. To find the latter, we have to recourse to a higher degree of theory, namely many-body perturbation theory (MBPT). Within MBPT, the most popular framework is the GW approximation (GWA) which describes electrons as quasiparticles (QP). The difference in energy between a non-interacting particle and a QP is called the self-energy. In GWA, the product of the Green function G and W, the screened Coulomb interaction, returns the self-energy. GWA is in principle self-consistent, but is mostly implemented as a perturbative correction to DFT results, known as G0W0. Unfortunately, the electronic structure given by G0W0 depends on the initial DFT results. This PhD project consists in the implementation of the self-consistent quasiparticle GW (QSGW) in the exciting code. This software package uses the all-electron linearized augmented planewave (LAPW) method, treating every electron on equal footing. Starting from DFT, the QSGW method (based in the GWA) optimizes the one-particle Hamiltonian through a self-consistent search for an optimized exchange-correlation potential. At the end of the iterative process, the QSGW method provides eigenfunctions and eigenvalues of the QPs. Considering nine crystalline solids, we present their electronic structure by means of QSGW. We present the bandstructures and density of state diagrams, comparing QSGW results to DFT and G0W0 results. In addition, we study the electronic charge density and wavefunction in selected materials.

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45

Segarra, Ortí Carlos. "Electronic structure of quantum dots: response to the environment and externally applied fields." Doctoral thesis, Universitat Jaume I, 2016. http://hdl.handle.net/10803/396165.

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En esta Tesis Doctoral se han estudiado teóricamente las propiedades electrónicas y ópticas de electrones y huecos confinados en puntos cuánticos semiconductores mediante el uso del método k·p dentro de las aproximaciones de masa efectiva y de función envolvente. Para tal fin, se han desarrollado modelos computacionales capaces de describir adecuadamente la estructura electrónica de las bandas de conducción y valencia de sistemas sometidos a varios fenómenos de interés. En concreto, se ha prestado especial atención a la respuesta de estas nanoestructuras frente a interacciones con el entorno (tensiones de deformación y piezoelectricidad) y a la aplicación de campos eléctricos y magnéticos externos. Adicionalmente, se ha estudiado la relajación de espín inducida por el acoplamiento espín-órbita teniendo en cuenta todas las posibles fuentes de mezcla de espín mediante modelos tridimensionales. Por último, se ha explorado también la aparición de estados de borde en nanoestructuras formadas por MoS2 monocapa.
In this PhD Thesis we theoretically investigate the optical and electronic properties of semiconductor nanostructures by using the k·p method within the effective mass and the envelope function approximations. To this end, computational models are built to properly describe the conduction and valence bands of nanoscopic systems subject to various relevant phenomena. Particularly, we focus on quantum dots of different shape, dimensions, and composition to explore their behavior under external magnetic fields and interactions with the environment such as strain and piezoelectricity. In addition, the spin-orbit-induced relaxation of the spin degree of freedom confined in quantum dots is also studied taking into account all relevant sources of spin mixing in fully three-dimensional models. Finally, we also study the emergence of edge states in nanoribbons and quantum dots of monolayer MoS2, which is a novel two-dimensional material. The obtained results reveal several interesting features which may be useful for future applications.

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46

Nauenheim, Christian [Verfasser]. "Integration of resistive switching devices in crossbar structures / Christian Nauenheim. Forschungszentrum Jülich GmbH, Institute of Solid State Research (IFF), Electronic Materials (IFF-6). [Hrsg.: Forschungszentrum Jülich GmbH, Zentralbibliothek]." Jülich : Forschungszentrum, Zentralbibliothek, 2009. http://d-nb.info/1008265985/34.

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47

Mamani, Rolando Larico. "Estrutura eletrônica e campo hiperfino de impurezas complexas de cobalto e de níquel em diamante." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-14032017-091058/.

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As várias possibilidades de aplicações tecnológicas que o material de diamante permite na indústria de dispositivos impulsionou os avanços ele fabricação de amostras de diamante sintético de alta qualidade. O diamante sintético crescido pela técnica de alta. pressão e alta temperatura (HPHT - High Pressure-High Temperature) utiliza ligas de metais de transição corno solvente-catalizadores. Dentre as várias impurezas de metal de transição introduzidas no material resultante, as impurezas de níquel são as mais bem caraterizaclas, pois os centros relacionados com Ni apresentam características especiais nestas amostras sintéticas. Medidas ele absorção óptica e de ressonância pararnagnética eletrônica têm identificado vários centros relacionados com a impureza de níquel em diamante, tanto isolados como complexos envolvendo defeitos intrínsecos ou dopantes. Entretanto, existem ainda muitas dúvidas sobre a estrutura microscópica destes centros. Neste trabalho apresentamos uma investigação teórica das propriedades eletrônicas e estruturais de impurezas relacionadas com níquel em diamante.
High quality synthetic diamond can be grown from gmphite by high pressure-high temperate menthols, using transition metal (TM) alloys ( containing manganese, iron, nickel, and cobalt) as catalysts. Nickel is the only TM which has been unambiguously identified as present in the resulting synthetic material. Electron paramagnetic resonance (EPR) and optical absorption measurements have identified Ni-related active centers in diamond mostly isolate Ni and Ni-related complexos involving intrinsic defects or dopants. However, there is considerable controversy about the microscopic structure of those centers. We present a theoretical investigation on the structural and electronic properties of nickel impurities in diamond.

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48

Pekkola, René [Verfasser], Wolfram [Akademischer Betreuer] Jaegermann, and Heinz von [Akademischer Betreuer] Seggern. "Electronic Structure of Solid-State Dye-Sensitized Solar Cells: Synchrotron Induced Photoelectron Spectroscopy on Nanocrystalline TiO2, Newly Developed Dyes and Spiro-MeOTAD / René Pekkola. Betreuer: Wolfram Jaegermann ; Heinz von Seggern." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2014. http://d-nb.info/1110792689/34.

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49

Zhang, Kelvin Hongliang. "Structural and electronic investigations of In₂O₃ nanostructures and thin films grown by molecular beam epitaxy." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:de125918-b36f-47cc-b72d-2f3a27a96488.

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Transparent conducting oxides (TCOs) combine optical transparency in the visible region with a high electrical conductivity. In2O3 doped with Sn (widely, but somewhat misleadingly, known as indium tin oxide or ITO) is at present the most important TCO, with applications in liquid crystal displays, touch screen displays, organic photovoltaics and other optoelectronic devices. Surprisingly, many of its fundamental properties have been the subject of controversy or have until recently remained unknown, including even the nature and magnitude of the bandgap. The technological importance of the material and the renewed interest in its basic physics prompted the research described in this thesis. This thesis aims (i) to establish conditions for the growth of high-quality In2O3 nanostructures and thin films by oxygen plasma assisted molecular beam epitaxy and (ii) to conduct comprehensive investigations on both the surface physics of this material and its structural and electronic properties. It was demonstrated that highly ordered In2O3 nanoislands, nanorods and thin films can be grown epitaxially on (100), (110) and (111) oriented Y-stabilized ZrO2 substrates respectively. The mismatch with this substrate is -1.7%, with the epilayer under tensile strain. On the basis of ab initio density functional theory calculations, it was concluded that the striking influence of substrate orientation on the distinctive growth modes was linked to the fact that the surface energy for the (111) surface is much lower than for either polar (100) or non-polar (110) surfaces. The growth of In2O3(111) thin films was further explored on Y-ZrO2(111) substrates by optimizing the growth temperature and film thickness. Very thin In2O3 epilayers (35 nm) grew pseudomorphically under high tensile strain, caused by the 1.7% lattice mismatch with the substrate. The strain was gradually relaxed with increasing film thickness. High-quality films with a low carrier concentration (5.0  1017 cm-3) and high mobility (73 cm2V-1s-1) were obtained in the thickest films (420 nm) after strain relaxation. The bandgap of the thinnest In2O3 films was around 0.1 eV smaller than that of the bulk material, due to reduction of bonding-antibonding interactions associated with lattice expansion. The high-quality surfaces of the (111) films allowed us to investigate various aspects of the surface structural and electronic properties. The atomic structure of In2O3 (111) surface was determined using a combination of scanning tunnelling microscopy, analysis of intensity/voltage curves in low energy electron diffraction and first-principles ab initio calculations. The (111) termination has an essentially bulk terminated (1 × 1) surface structure, with minor relaxations normal to the surface. Good agreement was found between the experimental surface structure and that derived from ab initio density functional theory calculations. This work emphasises the benefits of a multi-technique approach to determination of surface structure. The electronic properties of In2O3(111) surfaces were probed by synchrotron-based photoemission spectroscopy using photons with energies ranging from the ultraviolet (6 eV) to the hard X-ray regime (6000 eV) to excite the spectra. It has been shown that In2O3 is a highly covalent material, with significant hybridization between O and In orbitals in both the valence and the conduction bands. A pronounced electron accumulation layer presents itself at the surfaces of undoped In2O3 films with very low carrier concentrations, which results from the fact the charge neutrality level of In2O3 lies well above the conduction band minimum. The pronounced electron accumulation associated with a downward band bending in the near surface region creates a confining potential well, which causes the electrons in the conduction band become quantized into two subband states, as observed by angle resolved photoemission spectra (ARPES) Fermi surface mapping. The accumulation of high density of electrons near to the surface region was found to shrink the surface band gap through many body interactions. Finally epitaxial growth of In2O3 thin films on α-Al2O3(0001) substrates was investigated. Both the stable body centred cubic phase and the metastable hexagonal corundum In2O3 phase can be stabilized as epitaxial thin films, despite large mismatches with the substrate. The growth mode involves matching small but different integral multiples of lattice planes of the In2O3 and the substrate in a domain matching epitaxial growth mode.

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50

LOPEZ, MARCIO A. P. A. "Simulação e bombeio de cavidade OPO por um laser @1064nm CW multimodo de alta potência e polarizado." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28043.

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Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-22T17:35:38Z No. of bitstreams: 0
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O projeto de doutorado tem como objetivo estudo e montagem de um sistema laser que gere feixe laser de comprimento de onda sintonizável continuamente, com intervalo espectral na região infravermelho (IV) próximo e médio. O trabalho foi dividido em três partes: (i) laser de Nd:YAG @1064nm, (ii) aplicação deste sobre uma cavidade ressonante OPO e (iii) simulação de cavidades laser em anel. O laser de Nd:YAG foi montado e aprimorado a partir de outro laser desenvolvido anteriormente, o qual foi transformado em fonte polarizada pela inserção de um elemento óptico no seu interior. Em comparação com o laser não polarizado, ele apresentou potência de saída com valores relativamente altos, com um máximo de 30W, e melhora do fator de qualidade do feixe de M2<1,3 mais próximo do valor ideal igual a 1 e assim próximo do modo TEM00, adequado para aplicações de transferência de energia. A aplicação do laser Nd:YAG polarizado sobre uma cavidade OPO linear (meio ativo: cristal de Niobato de Lítio dopado 5%MgO:LiNbO3 com alternância de polarização, conhecido pela sigla PPLN) foi bem sucedida, por ter sido observado seu funcionamento pela geração em seu meio ativo dos feixes (λS, λC) sinal e complementar sintonizados continuamente, mostrando que valores de potência e fator de qualidade foram adequados e suficientes para ser testado em um OPO. Foi mensurada na saída potencia de 1W para o feixe complementar, onde a eficiência de inclinação da curva mostrou valores de 20,8% e 23,4% para bombeio pulsado (temperaturas do cristal TC=100°C/150°C), e o valor de 11,1% (TC=150°C) para bombeio contínuo. A aplicação da técnica knife-edge no feixe complementar (TC=150°C/rede periódica do cristal Λ0=31,59m/ λC=2470nm) resultou em fator de qualidade do feixe de M2=5,75(165). Foi realizada simulação numérica, visando estudo e planejamento de duas cavidades em anel simétricas, com sintonização contínua dos feixes de interesse na saída. A primeira contém um cristal PPLN como meio ativo, onde ocorre Oscilação Paramétrica, gerando feixe na região espectral do IV médio. A segunda cavidade possui dois cristais, que são PPLN e Triborato de Lítio (LiB3O5 conhecido pela sigla LBO), onde ocorrem na ordem Oscilação Paramétrica e Geração de Segundo Harmônico, gerando feixe na região espectral entre visível e IV próximo. Foram obtidos dois conjuntos de valores de dimensões para as cavidades, usando base teórica e condições de contorno apropriadas ao realizar os cálculos necessários, fixadas as informações sobre os respectivos componentes ópticos, onde o feixe de bombeio @1064nm focalizado no centro do cristal PPLN possui valor de cintura de feixe pouco maior que 50 μm. O laser de Nd:YAG @1064nm polarizado desenvolvido possui montagem simples e custo baixo de seus componentes, reduzindo o custo do sistema laser final onde foi aplicado, comparado com outros sistemas laser sintonizáveis. Deseja-se estudar o desenvolvimento destes para um modelo de frequência única, usando-o como fonte de bombeio para geração de feixes com largura de linha estreita, visando aplicação em espectroscopia.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

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