Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph.D.) -- Virginia Commonwealth University, 2004. / Title from title-page of electronic thesis. Prepared for: Dept. of Electrical Engineering. Bibliography: p. 114-125.

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Focused ion beam (FIB) technique uses a focused beam of ions to scan the surface of aspecimen, analogous to the way scanning electron microscope (SEM) utilizes electrons. Recent developments in the FIB technology have led to beam spot size below 10 nm,which makes FIB suitable for nanofabrication. This project investigated thenanofabrication aspect of the FIB technique, with device applications perspective inseveral directions. Project work included construction of an in-situ FIB electricalmeasurement system and development of its applications, direct measurements ofnanometer scale FIB cuts and fabrication and testing of lateral field emission devices. Research work was performed using a number of materials including Al, Cr, SiO2, Si3N4and their heterostructures. Measurements performed included in-situ resistometricmeasurements, which provided milled depth information by monitoring the resistancechange of a metal track while ion milling it. The reproducibly of this method wasconfirmed by repeating experiments and accuracy was proven by atomic force microscopy(AFM). The system accurately monitored the thickness of 50 nm wide and 400 nm thick(high aspect ratio) Nb tracks while ion milling them. Direct measurements of low aspectratio nanometer scale FIB cuts were performed using AFM on single crystal Si,polycrystalline Nb and an amorphous material. These experiments demonstrated theimportance of materials aspects for example the presence of grains for cuts at this scale. Anew lateral field emission device (in the plane of the chip) was fabricated, as FIB offersseveral advantages for these devices such as control over sharpness and decrease in anodeto-cathode spacing. FIB fabrication achieved field emission tip sharpness below 50 nm andanode-to-cathode spacing below 100 nm. For determining the field emission characteristicsof the devices, a low current (picoampere) measurement system was constructed anddevices operated in ultra high vacuum (10-9 mbar) in picoampere range. One devicefabricated using a FIB sharpening process had a turn on voltage of 57 V.

The effect of substrate surface topology on the interaction of living cells with inanimate substrates is a well-established phenomenon. When cells are placed on biomaterials, they outgrow protrusions called filopodia that sense surface features in their immediate surroundings and initiate the formation of stable cell adhesion complexes closer to the cell body. Adhesion proteins permit filopodia to constantly explore the surrounding microenvironment. A better understanding of the relationship of filopodia with surface features is highly relevant for exploiting custom-made surfaces to guide cell activity. In this work, mathematical modeling and simulation were used to describe different phenomena related to the interaction of a filopodium with its microenvironment, with the aim of reproducing experimentally observed phenomena associated to filopodia growth and interactions with substrates. The Kelvin Voigt model was used for the viscoelastic response of filopodia. Result predict filopodia protrusion under test conditions and helps improving our understanding on the effect of substrate topology on the biomechanical response of filopodial extensions.

The systematic study of the formation of β-SiC formed by low energy carbon ion (C-)implantation into Si followed by high temperature annealing is presented. The research is performed to explore the optimal annealing conditions. The formation of crystalline β-SiC is clearly observed in the sample annealed at 1100 °C for a period of 1 hr. Quantitative analysis is performed in the formation of β-SiC by the process of implantation of different carbon ion fluences of 1×1017, 2×1017, 5×1017, and 8×1017 atoms /cm2 at an ion energy of 65 keV into Si. It is observed that the average size of β-SiC crystals decreased and the amount of β-SiC crystals increased with the increase in the implanted fluences when the samples were annealed at 1100°C for 1 hr. However, it is observed that the amount of β-SiC linearly increased with the implanted fluences up to 5×1017 atoms /cm2. Above this fluence the amount of β-SiC appears to saturate. The stability of graphitic C-C bonds at 1100°C limits the growth of SiC precipitates in the sample implanted at a fluence of 8×1017 atoms /cm2 which results in the saturation behavior of SiC formation in the present study. Secondly, the carbon cluster formation process in silica and the characterization of formed clusters is presented. Silicon dioxide layers ~500 nm thick are thermally grown on a Si (100) wafer. The SiO2 layers are then implanted with 70 keV carbon ions at a fluence of 5×1017 atoms/cm2. The implanted samples are annealed 1100 °C for different time periods of 10 min., 30 min., 60 min., 90 min., and 120 min., in the mixture of argon and hydrogen gas (96 % Ar + 4% hydrogen). Photoluminescence spectroscopy reveals UV to visible emission from the samples. A detail mechanism of the photoluminescence and its possible origin is discussed by correlating the structural and optical properties of the samples. Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, spectroscopy, photoluminescence spectroscopy, and transmission electron microscopy are used to characterize the samples.

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