Thesis (Ph. D.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains viii, 113 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

Zugl.: Berlin, Freie Univ., Diss., 2009

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 120-124). Also available on the Internet.

Thesis (Ph. D.)--Florida State University, 2003. / Advisor: Dr. Zachary Fisk, Florida State University, College of Art and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed Mar. 2,2004). Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 120-132). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 120-132). Also available on the Internet.

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Semiconductor nanowire field-effect transistors (NWFET) have been recognized as a possible alternative to silicon-based CMOS technology as traditional scaling limits are neared. The core-shell nanowire structure, in particular, also allows for the enhancement of carrier mobility through radial band engineering. In this thesis, we have evaluated the possibility of electron confinement in strained Si-Si1-xGex core-shell nanowire heterostructures. Cylindrical strain distribution was calculated analytically for structures of various dimensions and shell compositions. The strain-induced conduction band edge shift of each region was found using k•p theory coupled with a coordinate system shift to account for strain. A positive conduction band offset of up to 200 meV was found for a Si-Si0.2Ge0.8 structure. We have also designed and characterized a modulation doping scheme for p-type, Ge-SiGe core-shell NWFETs. Finite element simulations of hole density versus radial position were done for different combinations of dopant position and concentration. Three modulation doped nanowire samples, each with a different boron doping density in the shell, were grown using a combined vapor-liquid-solid and chemical vapor deposition process. Low temperature current-voltage measurements of bottom- and top-gate samples indicate that hole mobility is limited by the proximity of charged impurities. / text

Colloidal quantum dots (CQDs) are an inexpensive and solution processable photovoltaic(PV) material reaching modest efficiencies of 6%. However, doping quantum dots still remains a challenge. This thesis explores the level of doping in lead sulfide (PbS)CQDs by surface ligands and bulk doping within the quantum dot lattice using metals. In light of the knowledge that oxygen creates traps on the surface of PbS CQDs, we have turned to the use of oxygen-free fabrication. We find that under a nitrogen environment, PbS CQD films are n-type and tunable in doping by use of halide ions. We show for the first time control over the doping density of n-type CQD films over a wide range. We also show the ability to fabricate p-type PbS films with high doping density that are compatible with n-type films. This compatibility enabled us to make the world’s first CQD homojunction PV device.

Colloidal quantum dots (CQDs) are an inexpensive and solution processable photovoltaic(PV) material reaching modest efficiencies of 6%. However, doping quantum dots still remains a challenge. This thesis explores the level of doping in lead sulfide (PbS)CQDs by surface ligands and bulk doping within the quantum dot lattice using metals. In light of the knowledge that oxygen creates traps on the surface of PbS CQDs, we have turned to the use of oxygen-free fabrication. We find that under a nitrogen environment, PbS CQD films are n-type and tunable in doping by use of halide ions. We show for the first time control over the doping density of n-type CQD films over a wide range. We also show the ability to fabricate p-type PbS films with high doping density that are compatible with n-type films. This compatibility enabled us to make the world’s first CQD homojunction PV device.