Application of FIB-SEM Techniques for the Advanced Characterization of Earth and Planetary Materials

Abstract

Advanced microanalytical techniques such as high-resolution transmission electron microscopy (HRTEM), atom probe tomography (APT), and synchrotron-based scanning transmission X-ray microscopy (STXM) enable one to characterize the structure and chemical and isotopic compositions of natural materials down towards the atomic scale. Dual focused ion beam-scanning electron microscopy (FIB-SEM) is a powerful tool for site-specific sample preparation and subsequent analysis by TEM, APT, and STXM to the highest energy and spatial resolutions. FIB-SEM also works as a stand-alone technique for three-dimensional (3D) tomography. In this review, we will outline the principles and challenges when using FIB-SEM for the advanced characterization of natural materials in the Earth and Planetary Sciences. More specifically, we aim to highlight the state-of-the-art applications of FIB-SEM using examples including (a) traditional FIB ultrathin sample preparation of small particles in the study of space weathering of lunar soil grains, (b) migration of Pb isotopes in zircons by FIB-based APT, (c) coordinated synchrotron-based STXM characterization of extraterrestrial organic material in carbonaceous chondrite, and finally (d) FIB-based 3D tomography of oil shale pores by slice and view methods. Dual beam FIB-SEM is a powerful analytical platform, the scope of which, for technological development and adaptation, is vast and exciting in the field of Earth and Planetary Sciences. For example, dual beam FIB-SEM will be a vital technique for the characterization of fine-grained asteroid and lunar samples returned to the Earth in the near future.

The Trends of In Situ Focused Ion Beam Technology: Toward Preparing Transmission Electron Microscopy Lamella and Devices at the Atomic Scale

“…The ion source in the current commercial system is the liquid metal ion source (LMIS), and the gallium (Ga) metal is widely used due to its low vapor pressure, low melting temperature (≈29.8 °C), and easy distinction from other elements. [40][41][42] By applying an elec tric field, the liquid Ga metal sticks to the tungsten (W) needle is pulled into a conical shape and forms an ≈2≈5 nm diameter tip. The electric field strength at the tip is as high as ≈10 10 V m −1 .…”

“…The sample is processed by the collision between ions and atoms, and the sputtering rate depends on the substrate material, the acceler ating voltage, and the incident angle of the ion beam. [40,44,45] For crosssectional observation, a higher beam current is usually employed for rough grinding, and then a lower beam current is used for fine polishing. Highenergy ion beams can induce uncontrollable damages to the sample, such as surface amor phous and ion implantation.…”

“…A schematic of the FIB–SEM system is illustrated in Figure a. [ 40 ] It is mainly composed of an ion beam system, an electron beam system, a gas injection system (GIS), and detectors. The direction of the ion beam and the vertical axis of the electron beam is fixed at an angle of ≈52°–55°.…”

“…Reproduced with permission. [ 40 ] Copyright 2021 Wiley Online Library. b) Principle diagram of ion beam etching.…”

Chemical and elemental mapping of spent nuclear fuel sections by soft X-ray spectromicroscopy

“…Although the FIB sections produced are relatively uniform in thickness, defects like voids and cracks present in the sample before FIB sectioning offer interesting points for investigation and useful references for image alignment, which is crucial for STXM analysis. FIB sections have been studied on a variety of samples from environmental (Benzerara et al, 2007) to archeological (Michelin et al, 2013;Bernard et al, 2009Bernard et al, , 2007 to interplanetary (Yabuta et al, 2014;Uesugi et al, 2014;Ito et al, 2020;Gu et al, 2020). FIB sections have also been used to study spent nuclear fuel recently (Clark et al, 2020;Kessler et al, 2020;Yuan et al, 2021;Liu et al, 2021;Teague & Gorman, 2014;Degueldre et al, 2016;Degueldre & Veleva, 2014).…”