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Title: High Brightness Ion Sources for Surface Analysis
Author: Dowsett, David Mark Francis
ISNI:       0000 0001 3431 7979
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2007
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The aim of this work was to produce an ion source with a high brightness and low energy spread. Two approaches were taken, an existing high brightness ion source (the liquid metal ion source) was monochromated to reduce its energy spread; this work was carried out at the University of York. The second approach was to develop a novel high brightness ion source with an intrinsically low energy spread. This approach was carried out at the University of Warwick. Several potential monochromators were simulated and the concentric hemispherical analyser was found to be the most suitable. Liquid metal ion sources were fabricated for monochromation by the author. However, these sources did not prove to be sufficiently stable for energy spread measurements and electron sources were used to try to demonstrate the principal. Ultimately this approach did not prove successful and the alternative ofdeveloping a novel source was pursued. This second approach utilises a novel emission process discovered at Warwick: surface enhanced field emission. Alkali metal vapours incident on a hot, chemically etched molybdenum wire are ionised at fields much lower than those normally required for field emission. Emission currents of several microamps have been obtained from the source and the sample current found to extremely stable with r.m.s noise of just 0.65%. The axial angular intensity of the source is 23 ~A sfl at 1 ~A emission. SIMS depth profiling has been carried out and the dynamic range at 1 keY was 3 orders of magnitude. Spot sizes of 20 ~m have been measured at 1 keY. The dynamic range and spot size do not represent the ultimate performance of the source, both are expected to improve in an ion column designed for a high brightness source.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available