No description available.

Thesis (M.Sc.)--Chinese University of Hong Kong. / Bibliography: leaf [4].

Herein, a program of research is detailed related to transport through the Si metal oxide semiconductor (MOS) quantum dots fabricated in a process flow compatible with modern ULSI (ultra large scale integrated circuit). Silicon quantum dots were fabricated by placing split gates within a MOSFET structure. Quantum dots of several sizes and geometries were fabricated by this process for the purpose of investigating the effects of size and shape on quantized transport through the dots. The transport properties of the different quantum dot sizes and shapes were investigated at low temperatures, and compared to normal MOSFETs fabricated by the same technology. Equilibrium measurements with the device biased in the regime from the onset of weak inversion to just past the onset of strong inversion revealed strongly oscillatory behavior in the tunneling conductance. The conductance peaks appear to map an energy level spectrum in the dot as the inversion and depletion gates are separately swept. Symmetric devices, biased both symmetrically and asymmetrically, show two groups of "branches" which evolve with different slopes in the V[subscript Inv]-V[subscript Depl] plane. An asymmetric device studied shows three groups of branches. In addition, a fine structure is observed in the conductance peak behavior of two devices. This apparent energy level structure is compared to the body of literature on the so-called artificial atoms, as well as self-consistent three dimensional quantum mechanical solutions for the energy levels in the same dot structure, which qualitatively agree with the overall slope of the observed data. However, the calculations reveal only the multiple sets of slopes when asymmetrically biased. These multiple slopes are postulated to arise due to the splitting of the degenerate states of the symmetric structure as the bias makes the structure increasingly asymmetric. Finally, a simplified model is presented which shows how slight asymmetry in the dot confining potential can give rise to both a fine structure and multiple slopes in the branches, and several alternative mechanisms are presented to explain the origin of the fine structure observed. / Graduation date: 2000

Synthesis of size tunable nanomaterials creates distinct chemo-physical properties. Recently, the popularity of magnetic iron oxide and cerium oxide (CeO2) nanocrystals enables researchers to use magnetic iron oxides (magnetite and ferrites) in size dependent magnetic separation and CeO2 as an automobile exhaust gas catalyst. This research shows production of diameter-controlled monodisperse magnetic iron oxide (ranging from 3 to 40 nm in diameter) and CeO2 (from 3 to 10 nm in diameter) nanocrystals with exceptional narrow diameter distribution (σ<10%). The morphology and composition of the nanocrystals were varied by use of diverse metal precursors, reaction temperature, time, cosurfactants, and molar ratio between metal salt and surfactant. Now the narrow diameter distributions of preformed magnetic iron oxide nanocrystals made it possible to grow diameter controlled uniform CNTs. The correlation between aluminum ferrite nanocrystal diameter and CNT diameter was nearly one. Additionally, we could synthesize the highest percentage (60%) of single walled CNTs from the smallest aluminum ferrite nanocrystals (4.0 nm). Because of the synthesis of uniform nanocrystalline CeO2, we could study diameter dependent antioxidant properties of nanocrystalline CeO2; antioxidant capacity of CeO2 was nine times higher than a known commercial standard antioxidant, Trolox. In addition, the smallest CeO2 nanocrystal (4 nm) decreased the oxidative stress of human dermal fibroblasts (HDF) exposed to hydrogen peroxide. These works suggest better understanding of monodisperse nanocrystal synthetic mechanism and potential uses of the materials, such as high quality CNT growth using magnetic iron oxides as precursor catalysts and the reduction of oxidative stress in cells using monodisperse CeO2 nanocrystal as an antioxidant for reactive oxygen species in biological media.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisors: Sanjay K. Banerjee and Amitabh Jain. Vita. Includes bibliographical references. Available also from UMI Company.

Thesis--M. Phil., University of Hong Kong, 1984.

published_or_final_version / Physics / Master / Master of Philosophy

No description available.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1986. / Bibliography: leaves 308-310. / Photocopy. / xxix, 310 leaves, bound ill. 29 cm

Thesis (M.S.)--Rochester Institute of Technology, 1992. / Typescript. Includes bibliographical references.