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Laser – Induced Nanostructures In Silicon, Jason Fowlkes

Doctoral Dissertations

This dissertation addresses the formation of nanostructures induced by the laser irradiation of silicon. A KrF (248 nm) pulsed excimer laser was used as the irradiation source. Irradiating micro – structured substrates in a reactive O2 atmosphere produced SiO nanostructures. Si nanoparticles were formed by irradiating both flat and micro – structured silicon surfaces in an inert gas ambient. On flat surfaces, low energy density irradiation (Ed < 1 J/cm2) induces the formation and clustering of a thin silicon film pulsed – laser deposited on silicon into nanoparticles that grow to 2 – 80 nm in diameter. Control over the Si nanoparticle diameter to within ± 1 nm could be obtained by optimizing the laser beam energy density, the inert gas pressure, and the number of laser pulses. The nanoparticles in the surface plane will self – organize into periodically spaced lines, if a periodic or quasi – periodic, microstructure is present at the surface.

A film of silicon nanoparticles was formed on the surface of a silicon target following pulsed laser irradiation in an inert, background gas. Silicon species generated during laser ablation were backscattered by the …

The Effect Of Implantation Temperature And Ionizing Radiation On The Microstructure Of Ion Implanted Sapphire, Lawretta Chineze Leaticia Ononye

Doctoral Dissertations

Single crystalline specimens of aluminum oxide (Al_{2O3) were irradiated with boron, nitrogen and iron ions at room temperature and 1000^{oC to fluences of 1×1017 B+/cm2, 3×1016 N+/cm2 and 1×1017 Fe+/cm2 respectively with 150 keV of energy. Following irradiation, the structures were examined by several experimental techniques: transmission electron microscopy (TEM), Rutherford backscattering - ion channeling (RBS-C) spectroscopy, optical absorption measurements, x-ray diffraction (XRD) technique, and x-ray photoelectron spectroscopy (XPS). The samples implanted at room temperature were then annealed for one hour at 1000oC in a reducing (Ar-4%H2) gas and the microstructures examined.}}

The implantation temperature significantly influenced the …

Study Of Uv Curable Rubber-Toughened Epoxy Systems, Abhijeet A. Godbole

Masters Theses

Rubber-toughened epoxy resins are used extensively in various structural applications. Current thermal curing processes limit the possible structural designs and require higher inputs in terms of pressure, temperature and time. UV and electron beam curing offers almost instantaneous curing of even complex structural shapes using minimal inputs. Various formulations were quenched from single phase at high temperatures to various temperatures below the corresponding cloud point temperatures, before being allowed to cool to room temperature. These quenched formulations were then cured using UV and thermal energy. The cured material toughness increases with decreasing particle size by over 150%. The rate of …