High Five: Resolution, Sensitivity, in operando Control, Ultra High Vacuum and Ion Sectioning in a Single Instrument

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The proposed instrument is a novel combination of ultra-high vacuum (UHV) Plasma Focused Ion Beam SIMS (PFIB-SIMS) that provides a step change in performance of state-of-the-art instrumentation in terms of resolution, sensitivity and applicability. Additional features are dual dynamic positive and negative ion detection, micro-structural analysis, electrical and thermal control for the performance of in operando studies and handling of air-sensitive materials by the incorporation of a pre-chamber. This design, unique worldwide, will enable the chemical quantification of complex surfaces with nanometric resolution and 3D chemical and microstructural reconstruction filling the dimensionality gap in the existing SIMS and FIB technology. The configuration and components used are at the forefront of materials sectioning and surface characterisation design in a UHV environment. The source of the secondary ions is the gas plasma focused ion beam (FIB) source and column that can produce either oxygen ions or xenon ions with a focus of 25nm for the highest lateral resolutions. This source is also able to section hard and soft materials to length scales of up to a millimetre for sub-surface bulk features by 3D serial-sectioning and characterisation. Low energy surface dosing with caesium is also available for enhancing the secondary ion yields of electronegative elements (e.g. O).Simultaneous positive and negative SIMS ion detection has been pioneered at Imperial College and is now optimised by ion trajectory modelling in this unique SIMS analysis configuration. Samples with both roughness and form are suitable as low electrical fields are inherent for signal extraction by the two electric quadrupole-based mass spectrometers. Sample cooling and heating is available, also in-situ-electrical contacts for IV testing and grounding at sample surfaces.Apart from the usual loadlock for a UHV instrument, there will be a second preparation/load-lock chamber for sample processing by temperature control and electrical contacts to mirror the main SIMS analysis chamber facilities. Additionally it will be possible to control the anneal gas ambient to atmospheric pressure with a gas analysis facility. The preparation/load-lock chamber provides a means of transferring air-sensitive samples in vacuum or gas environment from other preparation and characterisation facilities such as a dry Glove-box, SEM, XPS, and Diamond for example. A unique feature of the instrument configuration is the provision for obtaining optical images from samples in both load-locks including optical interference images for topography assessment.The instrument configuration is designed with inherent future-proofing in mind as both the analysis chamber and the preparation/load-lock have large volumes and spare access ports. In the analysis chamber, the use of a large working distance, ~15mm, low electric field extraction for the SIMS signal and accurate 5-axis stage movements means that there is available solid-angle access to the sample target position within the analysis chamber.The instrument will be placed in an existing specialist surface analysis laboratory where high performance SIMS/LEIS equipment is located and staffed by permanent ion beam specialists with world leading expertise in optimising ion beam analysis conditions and methodologies. Finally, assistance in data interpretation will be available to the user as well expertise in the operation of High Five.