Ấn phẩm:
Synthesis and characterization of functional nanostructures
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Nanostructured materials or nanomaterials are generally considered to possess at least one dimension on the nanometer scale. The physical properties of nanomaterials often differ significantly from those of bulk materials, largely due to quantum size effects and surface effects. Because of these unique properties and their potential applications, there is a great deal of interest in developing methods for controlling the composition and morphology of nanostructures. This thesis describes approaches to the synthesis and characterization of several functional materials in a nanostructured form, including metal oxides, metal silicides, and compound semiconductors. These materials were chosen because they exhibit unique and useful electronic, magnetic, and optical properties.
The first chapter provides a brief introduction to nanotechnology, nanomaterials, and the organization of this thesis. The second chapter describes the synthesis and structural, elemental, and magnetic characterization of barium-doped lanthanum manganite nanocubes. Manganite is an attractive transition-metal-oxide system because there is an incredible variety in their electronic and magnetic properties that may be tuned by chemical doping. We developed a hydrothermal synthesis of manganite nanocubes
whose chemical doping was adjusted by changing the relative abundance of chemical precursors and the solution pH levels.
The third chapter presents a vapor-phase synthesis of iron monosilicide nanowires and the characterization of the product. The cubic B20-type intermetallic compound EFeSi is a narrow band-gap semiconductor and a Kondo insulator. The synthesis yields straight and branched single-crystalline FeSi nanowires. Magnetic and electrical measurements were performed on the nanowire ensembles and on individual nanowires and the results were discussed.
The following two chapters focus on semiconductor nanorods and axial nanorod heterostructures. Specifically, the fourth chapter explores a solution-liquid-solid method for the synthesis of cadmium chalcogenide nanorods with built-in heterojunctions. Structural, electrical and optical characterization of the heterostructures consistently demonstrated the success of this synthetic strategy. The final chapter presents an electroluminescence study on individual colloidal CdSe nanorods devices with a transistor geometry. The electrical and optical properties of the devices were measured simultaneously at low temperature. The devices displayed Coulomb blockade behavior at low bias voltages. At higher bias voltages, we observed a superlinear increase in current with bias, accompanied by electroluminescence with a broad spectral distribution. These measurements enabled us to explore the interplay between charge transport and light emission in a single-nanocrystal transistor and propose a light emission mechanism.
Tác giả
Ouyang, Lian
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Nơi xuất bản
Nhà xuất bản
Harvard University
Năm xuất bản
2006
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