Studies in Mixed Species Charged Particle Beam Dynamics.

Available from UMI in association with The British Library. Requires signed TDF. The high brightness (~10 ^6 A cm^{-1} sr^{-1}) and small virtual source size (<50nm) of liquid metal ion sources (LMIS) make them ideally suited to ion microprobe formation. The major contributor to the spot diameter in such microprobes is chromatic aberration, arising from the large energy spread, <Delta E>, of the source. The origin of this energy spread is believed to be Coulomb interactions between emitted ions, but is not well understood. This thesis reports new experimental <DeltaE> data for Ga and In capillary sources, rather than the more usual needle type, showing that <Delta E> is not dependent upon the flow impedance. Monte Carlo simulations are also presented demonstrating that Coulomb interactions between emitted ions are certainly sufficient to give rise to the observed values of <DeltaE >, but that the simple models of Knauer (30) and Gesley et al (18, 19) are inadequate to explain the complex interplay of processes which occur near the emitter. In particular, the apparent success of Knauer's predicted 2/3 power dependence of < DeltaE> on source current in explaining the cases of Ga and In is shown to be merely fortuitous. This thesis also describes the design, construction and evaluation of a 7-10 keV LMIS based microprobe for applications in Secondary Ion Mass Spectrometry (SIMS) and ion beam milling. This had to be built to commercial specifications and power supply limitations in particular led to the adoption of a novel pentode lens stack. The microprobe was found to be well able to meet the design specifications, focusing 1nA into a 1.5 mu m spot. Various applications of the microprobe are also discussed including ion beam milling and SIMS.