Nanoscale wires and molecules have remarkable electrical properties that make them well suited for new electronic devices. The projected device densities result in very small separation distances and therefore the possibility of device-device interactions. However, we do not know what impacts wire-wire interactions might have on the properties of closely spaced devices. If two quantum wires interact, what types of effects will there be on transport properties such as conductance? How would the coupling strength, length of wire, position of contact, or the energy of the electrons affect conductance? Understanding the effects of the interactions will assist the construction of efficient nanoscale devices.This thesis examined the effects of interaction on the low-field conductance using a simple classical model and two quantum models of coupled quantum wires fabricated electrostatically in the two-dimensional electron gas at the interface of the heterostructure A1GaAs/GaAs. We considered the effect of position and length of an interaction between two parallel quantum wires formed by hard wall boundaries and connected to electron reservoirs. Our second model consisted of two artificial molecular wires, i.e., parallel chains of quantum dots. We used a one-electron Schrodinger equation in the envelope approximation, a tight-binding Hamiltonian, and a recursive Green's function method to study the electron transport properties. Multi-parameter computations using a fortran-95 computer model provided data for an analysis of the relationships among conductance, the interaction strength, interaction location, and electron energy.In contrast to the monotonic changes predicted by the classical model, the lowfield conductance of interacting hard wall quantum wires varies in an oscillatory manner with the perturbing interaction strength and position. For electron energies below the first conductance plateau, Breit-Wigner resonances appear as a consequence of coupling. These conductance properties are explained with reference to quasi-bound states created by reflections at the end boundaries of the wires and the separating wall.At low electron energies, the conductance signature of a symmetric artificial molecule composed of serial quantum dots is a band of resonances. Coupled artificial molecular wires display a split-off molecular band with an energy separation that grows with the coupling strength and a bandwidth that narrows. The position of the Fermi energy relative to the molecular band states plays a dominant role in determining the lowfield conductance of interacting artificial molecules. The conductance variation with coupling ranges from oscillatory to monotonic, depending on the Fermi energy. Varying the atom-atom coupling position in the molecular wires causes a relatively small shift in the resonance band energies. / Department of Physics and Astronomy

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The objective of this investigation was to determine the electronic effects of the halogen atoms in dihaloketenes such as dichloroketene and dibromoketene.

Transmission electron microscopy (TEM) is a powerful and versatile tool for investigating nanomaterials. In this thesis, various transmission electron microscopy techniques are used to study the chemical and structural features of different types of inorganic nanoparticles of well-defined morphologies as well as their assemblies. The synthesis of spherical and anisotropic nanoparticles (iron oxide nanocubes and other morphologies, gadolinium orthophosphate nanorods, tungsten oxide nanowires and nanorods, palladium nanospheres, and facetted iron-manganese oxides hybrid nanoparticles) using thermal decomposition of metal complex precursors in high-boiling point organic solvents and hydrothermal process are described in details. Electron diffraction tomography (3D EDT) is a recently developed technique that is used to investigate the 3D structure of crystalline materials. Reciprocal space volume reconstruction of 3D EDT data of thin WO3 nanowires assembled into nanorods revealed single crystal domains of hexagonal symmetry. Moreover, the use of 3D EDT enabled to identify and solve the structures of individual GdPO4 nanorods in a mixed phase powder. The use of 3D EDT was extended using small-angle diffraction mode to investigate the packing arrangements and defects in nanoparticle assemblies. A high concentration of planar defects found in different nanoparticle assemblies highlights the competition between the fcc and hcp arrangements during the assembly process. Iron-manganese oxides hybrid nanoparticles with different three-dimensional configurations, i.e. core|shell and asymmetric facetted dimers, were investigated using a combination of several electron microscopy techniques (HRTEM, SAED, STEM-HAADF, EFTEM, EELS). The growth of the facetted cubic MnO phase onto preformed Fe3O4 seed particles occurs preferentially along the Fe3O4 nanocube edges forming a well-oriented crystalline interface despite the lattice mismatch and defects. Atomic resolution monitoring of the structural changes in Mn3O4|Fe3O4 and Fe3O4|Mn3O4 core|shell nanoparticles induced by the electron beam revealed a strain relief mechanism at the interface involving inhomogeneous diffusion of cations and defects creation. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.</p>

A dissertation submitted in fulfillment of the requirements for the degree of Master of Science in Physics at the University of the Witwatersrand. November 7th, 2016 / The spin-1=2 Kondo model describes an antiferromagnetic exchange interaction between an impurity spin and the spin-density of a Fermi gas. Although the thermodynamics of this system have been resolved, there are still some unanswered questions regarding its spatial features. The spatial region of correlation between the impurity spin and the spin-density of the Fermi gas is referred to as the Kondo screening cloud. For the case of anisotropic couplings, the cloud consists of four distinct components. In this dissertation we use the bosonization technique to derive both an exact numeric and an approximate analytic expression for the forward scattering longitudinal cloud at the Toulouse point. The expressions are then extended to incorporate the effects of a time-independent external magnetic field. The non-magnetic case displays universal scaling behavior, while the addition of an external magnetic field only slightly spoils the scaling in the vicinity of the crossover length (B) K , but remarkably not deep inside or outside the cloud. / MT2017

by Li Sun-wai, Victor. / Title and statement of responsibility also in Chinese. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1984. / Bibliography: leaves [44]-45.

by Chu Wing Fai. / Parallel title in Chinese characters. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1988. / Bibliography: leaves 89-92.

by Ip Tak-wa. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1989. / Bibliography: leaves 62-64.

by Chan, Siu Cheung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1989. / Bibliography: leaves 65.

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