Cryogenic Focused Ion Beam Research Articles

Microstructural Analysis of Deposited Alkali Metal in “Anode-Free” Solid-State Batteries

Lithium metal as an anode material can greatly boost energy and power density in solid-state batteries.[1] However, challenges like local contact loss and dendrite growth limit the applicable current density. It was shown previously that the lithium microstructure can greatly influence the electrochemical performance of lithium, e.g. the stripping capacity until pore formation occurs.[2]Solid-state-batteries (SSBs) manufactured without the use of an alkali metal reservoir are under intense investigation, as they may enable unmatched energy densities without the need to handle reactive and inherently unsafe alkali metal foils. In these reservoir-free cells (RFCs) the alkali metal is usually stored in the discharged cathode active material upon assembly and thus only deposited at the anode current collector within the first charging step. However, despite its expected influence on the electrochemical performance, the microstructure of freshly deposited lithium has yet to be analyzed. Up to now, the lack of a combination of suitable preparation and analyses tools restrict any study of the microstructure of thin alkali metal films.Within this study, we designed a workflow to reliably analyze the microstructure of thermally processed lithium and sodium films. Using a combination of cryogenic focused ion beam (FIB) preparation and electron back-scatter diffraction (EBSD), we were able to exclude any recrystallization during room temperature storage or FIB preparation. Therefore, this newly developed workflow was further used to study the microstructure of otherwise buried alkali metal films, which were deposited in so called “anode-free” or reservoir free cell designs.Our analyses show that the grain size of plated alkali metal films is independent on the microstructure of used current collector and generally consists of very large grains, albeit not as large as as-bought foil. Even more interesting, every single deposited film consists solely of columnar grains with grain boundaries oriented perpendicular to the solid electrolyte interface, marking a clear difference to using an alkali metal foil as the anode. Our results are confirmed at two different RFCs, namely Cu|LLZO|Li and Steel|LPSCl|Li. Generally, we believe our research on metal anodes will open up the possibility of tackling more advanced scientific questions previously impossible to answer.(1) Krauskopf, T., Richter, F. H., Zeier, W. G. & Janek, J. Physicochemical Concepts of the Lithium Metal Anode in Solid-State Batteries. Chem. Rev. 120, 7745–7794 (2020).(2) Singh, D. K., Fuchs, T. et al. Origin of the lithium metal anode instability in solid-state batteries during discharge. Matter 6, 1463–1483 (2023).

(Invited) Intermetallics Based on Sodium Chalcogenides Promote Stable Electrodeposition – Electrodissolution of Sodium Metal Anodes

Sodiophilic micro-composite films of sodium-chalcogenide intermetallics (Na2Te and Na2S) and Cu particles are fabricated onto commercial copper foam current collectors (Na2Te@CF and Na2S@CF). For the first time a controllable capacity thermal infusion process is demonstrated. Enhanced wetting by the metal electrodeposition leads to state-of-the-art electrochemical performance. For example, Na2Te@CF-based half-cells demonstrate stable cycling at 6 mA cm-2 and 6 mAh cm-2, corresponding to 54 μm of Na electrodeposited/electrodissolved by geometric area. Sodium metal battery (SMB, NMB) cells with Na3V2(PO4)3 (NVP) cathodes are stable at 30C (7 mA cm-2) and for 10,000 cycles at 5C and 10C. Cross-sectional cryogenic focused ion beam (cryo-FIB) microscopy details deposited and remnant dissolved microstructures. Sodium metal deposited onto Na2Te@CF is dense, smooth, and free of dendrites or pores. On unmodified copper foam, sodium grows in a filament-like manner, not requiring cycling to achieve this geometry. Substrate-metal interaction critically affects the metal-electrolyte interface, namely the thickness and morphology of the solid electrolyte interphase (SEI). Density functional theory (DFT) and mesoscale simulations provide insight into support-adatom energetics, nucleation response, and early-stage morphological evolution. On Na2Te sodium atomic dispersion is thermodynamically more stable than isolated clusters, leading to conformal adatom coverage of the surface.

The advent of preventive high-resolution structural histopathology by artificial-intelligence-powered cryogenic electron tomography.

Advances in cryogenic electron microscopy (cryoEM) single particle analysis have revolutionized structural biology by facilitating the in vitro determination of atomic- and near-atomic-resolution structures for fully hydrated macromolecular complexes exhibiting compositional and conformational heterogeneity across a wide range of sizes. Cryogenic electron tomography (cryoET) and subtomogram averaging are rapidly progressing toward delivering similar insights for macromolecular complexes in situ, without requiring tags or harsh biochemical purification. Furthermore, cryoET enables the visualization of cellular and tissue phenotypes directly at molecular, nanometric resolution without chemical fixation or staining artifacts. This forward-looking review covers recent developments in cryoEM/ET and related technologies such as cryogenic focused ion beam milling scanning electron microscopy and correlative light microscopy, increasingly enhanced and supported by artificial intelligence algorithms. Their potential application to emerging concepts is discussed, primarily the prospect of complementing medical histopathology analysis. Machine learning solutions are poised to address current challenges posed by "big data" in cryoET of tissues, cells, and macromolecules, offering the promise of enabling novel, quantitative insights into disease processes, which may translate into the clinic and lead to improved diagnostics and targeted therapeutics.

Mechanical Milling – Induced Microstructure Changes in Argyrodite LPSCl Solid‐State Electrolyte Critically Affect Electrochemical Stability

AbstractMicrostructure of argyrodite solid‐state electrolyte (SSE) critically affects lithium metal electrodeposition/dissolution. While the stability of unmodified SSE is mediocre, once optimized state‐of‐the‐art electrochemical performance is achieved (symmetric cells, full cells with NMC811) without secondary interlayers or functionalized current collectors. Planetary mechanical milling in wet media (m‐xylene) is employed to alter commercial Li6PS5Cl (LPSCl) powder. Quantitative stereology demonstrates how milling progressively refines grain and pore size/distribution in the SSE compact, increases its density, and geometrically smoothens the SSE‐Li interface. Mechanical indentation demonstrates that these changes lead to reduced site‐to‐site variation in the compact's hardness. Milled microstructures promote uniform early‐stage electrodeposition on foil collectors and stabilize solid electrolyte interphase (SEI) reactivity. Analysis of half‐cells with bilayer electrolytes demonstrates the importance of microstructure directly contacting current collector, with interface roughness due to pore and grain size distribution being key. For the first time, short‐circuiting Li metal dendrite is directly identified, employing 1.5 mm diameter “mini” symmetrical cell and cryogenic focused ion beam (cryo‐FIB) electron microscopy. The branching sheet‐like dendrite traverses intergranularly, filling the interparticle voids and forming an SEI around it. Mesoscale modeling reveals the relationship between Li‐SSE interface morphology and the onset of electrochemical instability, based on underlying reaction current distribution.

Conjugate Multimode Heat Transfer Analysis of Cryogenic EXLO Manipulation.

In this study, a conjugate radiation/conduction multimode heat transfer analysis of cryogenic focused ion beam (FIB) milling steps necessary for producing ex situ lift out specimens under cryogenic conditions (cryo-EXLO) is performed. Using finite volume for transient heat conduction and enclosure theory for radiation heat transfer, the analysis shows that as long as the specimen is attached or touching the FIB side wall trenches, the specimen will remain vitreous indefinitely, while actively cooled at liquid nitrogen (LN2) temperatures. To simulate the time needed to perform a transfer step to move the bulk sample containing the FIB-thinned specimen from the cryo-FIB to the cryo-EXLO cryostat, the LN2 temperature active cooling is turned off after steady-state conditions are reached and the specimen is monitored over time until the critical devitrification temperature is reached. Under these conditions, the sample will remain vitreous for >3 min, which is more than enough time needed to perform the cryo-transfer step from the FIB to the cryostat, which takes only ∼10 s. Cryo-transmission electron microscopy images of a manipulated cryo-EXLO yeast specimen prepared with cryo-FIB corroborates the heat transfer analysis.

Scalable substrate development for aqueous sample preparation for atom probe tomography.

Reliable and consistent preparation of atom probe tomography (APT) specimens from aqueous and hydrated biological specimens remains a significant challenge. One particularly difficult process step is the use of a focused ion beam (FIB) instrument for preparing the required needle-shaped specimen, typically involving a "lift-out" procedure of a small sample of material. Here, two alternative substrate designs are introduced that enable using FIB only for sharpening, along with example APT datasets. The first design is a laser-cut FIB-style half-grid close to those used for transmission-electron microscopy, that can be used in a grid holder compatible with APT pucks. The second design is a larger, standalone self-supporting substrate called a "crown," with several specimen positions that self-aligns in APT pucks, prepared by electrical discharge machining (EDM). Both designs are made nanoporous, to provide strength to the liquid-substrate interface, using chemical and vacuum dealloying. We select alpha brass a simple, widely available, lower-cost alternative to previously proposed substrates. We present the resulting designs, APT data, and provide suggestions to help drive wider community adoption. Lay Description Atom probe tomography (APT) maps the composition of solid materials in three dimensions with sub-nanometre resolution. Preparation of specimens from aqueous specimens remains a significant challenge. To aid with preparation, we introduce here two substrate designs that can hold suitable volumes of liquid for freezing, prior to shaping the final specimen into a sharp needle for APT by using cryogenic focused ion beam milling. We also describe the complete setup that we designed for handling these substrates, including dedicated sample holders. Both substrates are made nanoporous, to provide strength to the liquid-substrate interface, using chemical and vacuum dealloying of alpha brass a simple, widely available, low-cost material. We finally showcase APT data and provide suggestions to help drive wider community adoption. This article is protected by copyright. All rights reserved.

(Invited) Understanding the Interphasial Phenomena in ALL SOLID State Batteries

Compared with the liquid-electrolyte analogues, solid state electrolytes SSEs have drawn increased attention as they promote battery safety, exhibit a wide operational temperature window, and improve energy density by enabling Li metal as anode materials for next-generation lithium-ion batteries. Despite suitable mechanical properties to prevent Li dendrite penetration, relatively wide electrochemical stability windows, comparable ionic conductivities, and intrinsic safety, most SSEs are found to be thermodynamically unstable against Li metal, where SSE decomposition produces a complex interphase, analogous to the SEI formed in liquid electrolyte systems. An ideal passivation layer should consist of ionically conductive but electronically insulating components to prevent the SSE from being further reduced. The past four decades have witnessed intensive research efforts on the chemistry, structure, and morphology of the solid electrolyte interphase (SEI) in Li-metal and Li-ion batteries (LIBs) using liquid or polymer electrolytes, since the SEI is considered to predominantly influence the performance, safety and cycle life of batteries. Study of the buried interfaces in solid state electrolytes has been challenging. Originating from the structural biology field, cryogenic focused ion beam (cryo-FIB) and cryogenic electron microscopy (cryo-EM) have recently been introduced to battery research, and have proven the ability to preserve and probe Li metal for quantitative structural and chemical analysis. All-solid-state batteries (ASSBs) have been promoted as a highly promising energy storage technology due to the prospects of improved safety and a wider operating temperature range compared to their conventional liquid electrolyte-based counterparts. While solid electrolytes with ionic conductivities comparable to liquid electrolytes have been discovered, fabricating solid-state full cells with high areal capacities that can cycle at reasonable current densities remains a principal challenge. To overcome these challenges, a quantitative and in-depth understanding of the phenomena governing ionic and electronic transport limitations within the cathode composite, in addition to mechanical aspects arising from significant volume changes associated with Li metal anodes (including anode-less cell designs) are needed. Such understanding can be obtained from proper electrochemical measurements described herein. In this talk, we will highlight solutions to these existing challenges and several directions for future work are proposed.

A Customized Hydrophobic Porous Shell for MOF-5.

The susceptibility to moisture of metal-organic frameworks (MOFs) is a critical bottleneck for their wider practical application. Constructing core-shell composites has been postulated as an effective strategy for enhancing moisture resistance, but for fragile MOFs this has rarely been accomplished. We report herein, for the first time, the construction of a customized hydrophobic porous shell, NTU-COF, on the particularly fragile MOF-5 by a "Plug-Socket Anchoring" strategy. Notably, the pore structure of MOF-5 was well maintained, and it could still achieve complete CO2/N2 separation under humid conditions. The homogeneous interface between MOF-5 and NTU-COF has been inspected at atomic resolution by a combination of cryogenic focused ion beam (cryo-FIB) and ultralow-dose (scanning) transmission electron microscope giving profound insight into the mechanism of assembly of the core-shell structure. This work presents a facile strategy for the fabrication of a hydrophobic porous shell for labile MOFs, and provides a general approach for solving the problem of moisture instability of porous materials for practical applications.

Intermetallics Based on Sodium Chalcogenides Promote Stable Electrodeposition–Electrodissolution of Sodium Metal Anodes

AbstractSodiophilic micro‐composite films of sodium‐chalcogenide intermetallics (Na2Te and Na2S) and Cu particles are fabricated onto commercial copper foam current collectors (Na2Te@CF and Na2S@CF). For the first time a controllable capacity thermal infusion process is demonstrated. Enhanced wetting by the metal electrodeposition leads to state‐of‐the‐art electrochemical performance. For example, Na2Te@CF‐based half‐cells demonstrate stable cycling at 6 mA cm−2 and 6 mAh cm−2, corresponding to 54 µm of Na electrodeposited/electrodissolved by geometric area. Sodium metal batteries with Na3V2 (PO4)3 cathodes are stable at 30C (7 mA cm−2) and for 10 000 cycles at 5C and 10C. Cross‐sectional cryogenic focused ion beam (cryo‐FIB) microscopy details deposited and remnant dissolved microstructures. Sodium metal electrodeposition onto Na2Te@CF is dense, smooth, and free of dendrites or pores. On unmodified copper foam, sodium grows in a filament‐like manner, not requiring cycling to achieve this geometry. Substrate–metal interaction critically affects the metal–electrolyte interface, namely the thickness and morphology of the solid electrolyte interphase. Density functional theory and mesoscale simulations provide insight into support‐adatom energetics, nucleation response, and early‐stage morphological evolution. On Na2Te sodium atomic dispersion is thermodynamically more stable than isolated clusters, leading to conformal adatom coverage of the surface.

FIB‐SEM and ToF‐SIMS Analysis of High‐Temperature PEM Fuel Cell Electrodes

AbstractThe phosphoric acid (PA) distribution in the electrodes is a crucial factor for the performance of high‐temperature polymer electrolyte fuel cells (HT‐PEM FCs). Therefore, understanding and optimizing the electrolyte distribution is vital to maximizing power output and achieving low degradation. Although challenging, tracking the PA in nanometer‐sized pores is essential because most active sites in the commonly used carbon black‐supported catalysts are located in pores below 1 µm. For this study, a cell is operated at 200 mA cm−2 for 5 days. After this break‐in period, the cathode is separated from the membrane electrode assembly and subsequently investigated by cryogenic focused ion beam scanning electron microscopy (cryo FIB‐SEM) coupled with energy‐dispersive X‐ray spectroscopy (EDX) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). PA is located on the surface and in the bulk of the cathode catalyst layer. In addition, the PA distribution can be successfully linked to the gas diffusion electrode morphology and the binder distribution. The PA preferably invades nanometer‐sized pores and is uniformly distributed in the catalyst layer.

Cryo-electron tomography on focused ion beam lamellae transforms structural cell biology.

Cryogenic electron microscopy and data processing enable the determination of structures of isolated macromolecules to near-atomic resolution. However, these data do not provide structural information in the cellular environment where macromolecules perform their native functions, and vital molecular interactions can be lost during the isolation process. Cryogenic focused ion beam (FIB) fabrication generates thin lamellae of cellular samples and tissues, enabling structural studies on the near-native cellular interior and its surroundings by cryogenic electron tomography (cryo-ET). Cellular cryo-ET benefits from the technological developments in electron microscopes, detectors and data processing, and more in situ structures are being obtained and at increasingly higher resolution. In this Review, we discuss recent studies employing cryo-ET on FIB-generated lamellae and the technological developments in ultrarapid sample freezing, FIB fabrication of lamellae, tomography, data processing and correlative light and electron microscopy that have enabled these studies. Finally, we explore the future of cryo-ET in terms of both methods development and biological application.

Cryo-EXLO Manipulation of FIB Specimens for Cryo-TEM

Abstract This work describes cryogenic ex situ lift out (cryo-EXLO) of cryogenic focused ion beam (cryo-FIB) thinned specimens for analysis by cryogenic transmission electron microscopy (cryo-TEM). The steps and apparatus necessary for cryo-EXLO are described. Methods designed to limit ice contamination include use of an anti-frost lid, a vacuum transfer assembly, and a cryostat. Cryo-EXLO is performed in a cryostat with the cryo-shuttle holder positioned in the cryogenic vapor phase above the surface of liquid N2 (LN2) using an EXLO manipulation station installed inside a glove box maintained at < 10% relative humidity and inert (e.g., N2 gas) conditions. Thermal modeling shows that a cryo-EXLO specimen will remain vitreous within its FIB trench indefinitely while LN2 is continuously supplied. Once the LN2 is cut off, modeling shows that the EXLO specimen will remain vitreous for over 4 min, allowing sufficient time for the cryo-transfer steps which take only seconds to perform. Cryo-EXLO was applied successfully to cryo-FIB-milled specimen preparation of a polymer sample and plunge-frozen yeast cells. Cryo-TEM of both the polymer and the yeast shows minimal ice contamination with the yeast specimen maintaining its vitreous phase, illustrating the potential of cryo-EXLO for cryo-FIB-TEM of beam-sensitive, liquid, or biological materials.

In Situ Imaging of Virus-Infected Cells by Cryo-Electron Tomography: An Overview.

Cryo-electron tomography (cryo-ET) has emerged as a powerful tool in structural biology to study viruses and is undergoing a resolution revolution. Enveloped viruses comprise several RNA and DNA pleomorphic viruses that are pathogens of clinical importance to humans and animals. Considerable efforts in cryogenic correlative light and electron microscopy (cryo-CLEM), cryogenic focused ion beam milling (cryo-FIB), and integrative structural techniques are helping to identify virus structures within cells leading to a rise of in situ discoveries shedding light on how viruses interact with their hosts during different stages of infection. This chapter reviews recent advances in the application of cryo-ET in imaging enveloped viruses and the structural and mechanistic insights revealed studying the viral infection cycle within their eukaryotic cellular hosts, with particular attention to viral entry, replication, assembly, and egress during infection.

Stable Anode-Free All-Solid-State Lithium Battery through Tuned Metal Wetting on the Copper Current Collector.

A stable anode-free all-solid-state battery (AF-ASSB) with sulfide-based solid-electrolyte (SE) (argyrodite Li6 PS5 Cl) is achieved by tuning wetting of lithium metal on "empty" copper current-collector. Lithiophilic 1µm Li2 Te is synthesized by exposing the collector to tellurium vapor, followed by insitu Li activation during the first charge. The Li2 Te significantly reduces the electrodeposition/electrodissolution overpotentials and improves Coulombic efficiency (CE). During continuous electrodeposition experiments using half-cells (1mAcm-2 ), the accumulated thickness of electrodeposited Li on Li2 Te-Cu is more than 70µm, which is the thickness of the Li foil counter-electrode. Full AF-ASSB with NMC811cathode delivers an initial CE of 83% at 0.2C, with a cycling CE above 99%. Cryogenic focused ion beam (Cryo-FIB) sectioning demonstrates uniform electrodeposited metal microstructure, with no signs of voids or dendrites at the collector-SE interface. Electrodissolution is uniform and complete, with Li2 Te remaining structurally stable and adherent. By contrast, an unmodified Cu current-collector promotes inhomogeneous Li electrodeposition/electrodissolution, electrochemically inactive "dead metal," dendrites that extend into SE, and thick non-uniform solid electrolyte interphase (SEI) interspersed with pores. Density functional theory (DFT) and mesoscale calculations provide complementary insight regarding nucleation-growth behavior. Unlike conventional liquid-electrolyte metal batteries, the role of current collector/support lithiophilicity has not been explored for emerging AF-ASSBs.

A cryogenic, coincident fluorescence, electron, and ion beam microscope.

Cryogenic electron tomography (cryo-ET) combined with subtomogram averaging, allows in situ visualization and structure determination of macromolecular complexes at subnanometre resolution. Cryogenic focused ion beam (cryo-FIB) micromachining is used to prepare a thin lamella-shaped sample out of a frozen-hydrated cell for cryo-ET imaging, but standard cryo-FIB fabrication is blind to the precise location of the structure or proteins of interest. Fluorescence-guided focused ion beam (FIB) milling at target locations requires multiple sample transfers prone to contamination, and relocation and registration accuracy is often insufficient for 3D targeting. Here, we present in situ fluorescence microscopy-guided FIB fabrication of a frozen-hydrated lamella to address this problem: we built a coincident three-beam cryogenic correlative microscope by retrofitting a compact cryogenic microcooler, custom positioning stage, and an inverted widefield fluorescence microscope (FM) on an existing FIB scanning electron microscope. We show FM controlled targeting at every milling step in the lamella fabrication process, validated with transmission electron microscope tomogram reconstructions of the target regions. The ability to check the lamella during and after the milling process results in a higher success rate in the fabrication process and will increase the throughput of fabrication for lamellae suitable for high-resolution imaging.

Suppressing Chemical Corrosions of Lithium Metal Anodes

AbstractThe lithium metal anode is essential for next‐generation high‐energy‐density rechargeable Li‐metal batteries. Although extensive studies have been performed to prolong the cycle life of Li‐metal batteries, the calendar life, which associates with the chemical corrosion of Li metal in liquid electrolytes, has not been quantitatively understood. Here, by combing the titration gas chromatography method and cryogenic focused ion beam, a quantitative relationship between the chemical corrosion rate and electrochemically deposited Li morphology in various liquid electrolyte systems is established. It has been identified that the corrosion rate is dominated by the porosity of the deposited Li. The larger the porosity of deposited Li has, the faster the corrosion rate will be. Strategies to mitigate the chemical corrosion on Li thus to extend the calendar life of Li‐metal batteries are further proposed. By strictly controlling the stacking pressure during Li plating, Li deposits with ultra‐low porosity can be achieved, suppressing the corrosion rate to 0.08 ± 0.16%/day compared with 1.71 ± 0.19%/day of the high‐porosity Li.

Cryogenic Focused Ion Beam Sample Preparation for the Analysis of Hydrogen in Zr Alloy APT Experiments

Cryogenic Focused Ion Beam Sample Preparation for the Analysis of Hydrogen in Zr Alloy APT Experiments

Nanoscale Characterization of Liquid-Solid Interfaces by Coupling Cryo-Focused Ion Beam Milling with Scanning Electron Microscopy and Spectroscopy

Physical and chemical processes at solid-liquid interfaces play a crucial role in many natural and technological phenomena, including catalysis, solar energy and fuel generation, and electrochemical energy storage. Nanoscale characterization of such interfaces has recently been achieved using cryogenic electron microscopy, thereby providing a new path to advancing our fundamental understanding of interface processes. This contribution provides a practical guide to mapping the structure and chemistry of solid-liquid interfaces in materials and devices using an integrated cryogenic electron microscopy approach. In this approach, we pair cryogenic sample preparation which allows stabilization of solid-liquid interfaces with cryogenic focused ion beam (cryo-FIB) milling to create cross-sections through these complex buried structures. Cryogenic scanning electron microscopy (cryo-SEM) techniques performed in a dual-beam FIB/SEM enable direct imaging as well as chemical mapping at the nanoscale. We discuss practical challenges, strategies to overcome them, as well as protocols for obtaining optimal results. While we focus in our discussion on interfaces in energy storage devices, the methods outlined are broadly applicable to a range of fields where solid-liquid interface play a key role.

Bubbles and atom clusters in rock melts: A chicken and egg problem

Bubble and crystal nucleation and growth dynamics play a vital function in determining the eruptive behaviour of a magma. Investigating the initial stages of bubble nucleation and crystallization processes, including their rate and relative timing, can thus give us insight into the eruption parameters of magmas including their rheology. Although many experiments and numerical simulations of decompression-induced vesicle nucleation in magmas have been carried out, the mechanisms of bubble nucleation remain poorly understood. It is widely accepted that there are two ways bubbles can form: either by homogeneous nucleation within a melt, or by heterogeneous nucleation on a surface, interface, or particle. It has been tentatively suggested that what had been interpreted as homogeneous nucleation in magmas was instead heterogeneous nucleation on the surface of elusive nano- or micro-scale crystals present throughout the melt. Herein, we have conducted an experiment whereby bubble nucleation is induced in a synthetic andesitic glass sample using radiation damage from a focused ion beam (FIB) to investigate the initial stages of bubble nucleation. Scanning transmission electron microscopy, electron energy-loss spectroscopy and atom probe tomography (APT) data reveal sub-nanometer scale chemical heterogeneities in the form of Fe-, Na-, and/or Ca-rich clusters at the bubble-glass interface of the newly created bubbles. Comparatively, specimens prepared by cryogenic FIB, in which bubble nucleation is suppressed, are without bubbles; however, APT data shows similar chemical heterogeneities suggesting these clusters existed within the synthetic glass prior to bubble formation. Based on these observations, our data demonstrate the existence of nanoscale chemical heterogeneities within a synthetic silicate glass and at bubble-glass interfaces. Although our experiments do not replicate the conditions of natural processes, our results contribute to the hypothesis that previously described homogeneous nucleation may be re-interpreted as a variety of heterogeneous nucleation. These findings highlight the need to revise the commonly used definition of homogeneous nucleation among magma scientists.

Cryogenic Focused Ion Beam Enables Atomic-Resolution Imaging of Local Structures in Highly Sensitive Bulk Crystals and Devices.

With the development of ultralow-dose (scanning) transmission electron microscopy ((S)TEM) techniques, atomic-resolution imaging of highly sensitive nanomaterials has recently become possible. However, applying these techniques to the study of sensitive bulk materials remains challenging due to the lack of suitable specimen preparation methods. We report that cryogenic focused ion beam (cryo-FIB) can provide a solution to this challenge. We successfully extracted thin specimens from metal–organic framework (MOF) crystals and a hybrid halide perovskite single-crystal film solar cell using cryo-FIB without damaging the inherent structures. The high quality of the specimens enabled the subsequent (S)TEM and electron diffraction studies to reveal complex unknown local structures at an atomic resolution. The obtained structural information allowed us to resolve planar defects in MOF HKUST-1, three-dimensionally reconstruct a concomitant phase in MOF UiO-66, and discover a new CH3NH3PbI3 structure and locate its distribution in a single-crystal film perovskite solar cell. This proof-of-concept study demonstrates that cryo-FIB has a unique ability to handle highly sensitive materials, which can substantially expand the range of applications for electron microscopy.