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Field evaporation and desorption ion sources


Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/17454

Field evaporation and desorption ion sources

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Title: Field evaporation and desorption ion sources
Author: Solano, Isidro
Advisor(s): Schwoebel, Paul
Committee Member(s): Rudolph, Wolfgang
Dunlap, David
Department: University of New Mexico. Dept. of Physics & Astronomy
Subject: Crystal orientation relation, thin films, atom probe, field ion microscopy, Erbium, Tungsten, Field Evaporation, Field Desorption, Pitsch-Schrader, Titanium, Neutron Generator, Ion Source, Tin Oxide,
LC Subject(s): Deuterium ions.
Ion sources.
Metallic films.
Rare earth oxide thin films.
Degree Level: Masters
Abstract: Novel approaches to the production of deuterium ions were investigated as part of a program directed toward the development of high efficiency ion source for use in a fieldable neutron generator. The principle line of investigation was a source based on the field desorption of deuterium from the tip surfaces of microfabricated arrays. Using tip arrays, both desorption of atomic deuterium ions and gas phase field ionization of molecular deuterium was observed at fields of roughly 2 V/Å and 2-3 V/Å, respectively, at room temperature. Maximum fields of 3 V/Å have been applied to the array tip surfaces to date, although achieving fields of 2 V/Å to 2.5 V/Å was more typical. A second line of investigation was proof-of-principle experiments demonstrating an electrostatic field evaporation based deuterium ion source. This source produces atomic deuterium and metal ions by the field evaporation of deuterated metal films. During these studies the morphological structure of clean and deuterated Er and Ti films deposited on W substrates and their removal by field evaporation were investigated. It was observed that both titanium and deuterated titanium films deposited on W substrates at 77 K or 295 K were pseudomorphic with the underlying W <110> substrate. Well-annealed Er films thicker than ~ 20 layers formed a hexagonal close-packed <0001> orientated over layer with the Pitsch-Schrader orientation on the W <110> substrate. The pseudomorphic and hexagonal close-packed character of the films is retained up to the last atomic layer that forms the film-substrate interface. Deuterated Er films appear polycrystalline. At 77 K in Ar, annealed Er films field evaporate at 2.5 V/Å primarily as Er2+ and deuterated Er films evaporate at ~ 2.4 V/Å primarily as D+ and ErDx2+, 0 ≤ x ≤ 3. Field evaporation of both clean and deuterated Er and Ti films showed signs of space charge induced field lowering when film thicknesses exceeding ~10 layers were field evaporated using 20 ns duration voltage pulses. To aide in these investigations a simple tin oxide film deposition technique using a radio frequency induction heater to allow in situ visualization of the deposition process and resulting film was developed. Uniform films having resistivities as low as 2 mΩ-cm with transmittances of approximately 85% in the visible light spectrum were readily deposited.
Graduation Date: December 2011
URI: http://hdl.handle.net/1928/17454

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