Development of high-resolution focussed ion beam-secondary ion mass spectrometry (FIB-SIMS) as a tool for Earth and Materials sciences

Scanning electron microscopy (SEM) and focused ion beam - scanning electron microscopy (FIB-SEM) combined with energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) allow for compositional and crystallographic mapping of tens to hundreds of microns of area, with potentially 100 nm spatial resolution or better. The problem here is that EBSD and EDS are not sensitive to light elements or isotopes. In this project we will develop a new analytical tomographic approach using the FIB combined with secondary ion mass spectroscopy (SIMS). This tomographic technique will be integrated into a correlative approach using optical microscopy, x-ray tomography, transmission electron microscopy and atom probe tomography.

The microscopy techniques developed during this project will be used to address a variety of complex materials characterization problems in natural and synthetic samples. This includes characterizing the trace element and isotope compositions of inclusions found in zircons from the Jack Hills of Western Australia. Understanding the mineral ages of the inclusions found in these samples has the potential to unlock key outstanding questions in paleomagnetism, such as when did the Earth's magnetic field begin? Additionally, SIMS analysis of shale and sandstones will be used to understand dissolution and re-precipitation processes occurring at the pore scale relevant to understanding oil and gas reservoir behavior. This correlative analytical tomography will also be used to explore chemical behaviors in other materials important to energy storage, such as solid oxide batteries. Finally, this can be used to address light-element segregation along grain boundaries in steels and nuclear materials. FIB-SIMS enabled tomography directly addresses an analytical length-scale and information gap, which is important for the characterization of natural and synthetic materials.

This project focuses on exploring the potential of SIMS tomography FIB-SEM and ion beam microscopes to develop a mass spectroscopic technique that addresses the length scale information gap between ICPMS and APT. SIMS as an analytical technique offers information significantly differ from that traditionally measured using EDS analysis. Significantly, SIMS makes it is possible to analyze both isotope trace light element distributions in a sample with a spatial resolution of tens of nanometers. Further, the student will also design and implement experiments using this new tomography as part of an integrated workflow, going from x-ray and optical down to TEM or APT (mm to atoms). Maintaining a data connection across length scales.

The student will develop a new cutting edge analytical tomographic technique, combining the sequential sequencing of a sample using an ion beam and then combining it with SIMS data to create a three dimensional elemental map of the studied volume. This new technique will open up three-dimensional explorations into isotope and trace/ light element distributions through a sample. Using this technique the student will explore questions about fluid rock interactions and questions related to deep carbon. Further, technologically important materials related to the energy storage, and recovery as well as advanced metallurgical questions.