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Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010. [ABSTRACT FROM PUBLISHER]

Recent advances in theoretical structure prediction methods and high-throughput computational techniques are revolutionizing experimental discovery of the thermodynamically stable inorganic materials. Metastable materials represent a new frontier for these studies, since even simple binary non-ground state compounds of common elements may be awaiting discovery. However, there are significant research challenges related to non-equilibrium thin film synthesis and crystal structure predictions, such as small strained crystals in the experimental samples and energy minimization based theoretical algorithms. Here, we report on experimental synthesis and characterization, as well as theoretical first-principles calculations of a previously unreported mixed-valent binary tin nitride. Thin film experiments indicate that this novel material is N-deficient SnN with tin in the mixed ii/iv valence state and a small low-symmetry unit cell. Theoretical calculations suggest that the most likely crystal structure has the space group 2 (SG2) related to the distorted delafossite (SG166), which is nearly 0.1 eV/atom above the ground state SnN polymorph. This observation is rationalized by the structural similarity of the SnN distorted delafossite to the chemically related Sn3N4 spinel compound, which provides a fresh scientific insight into the reasons for growth of polymorphs of metastable materials. In addition to reporting on the discovery of the simple binary SnN compound, this paper illustrates a possible way of combining a wide range of advanced characterization techniques with the first-principle property calculation methods, to elucidate the most likely crystal structure of the previously unreported metastable materials. [ABSTRACT FROM AUTHOR]

The development of three-dimensional (3-D), characterisation techniques with high spatial and mass resolution is crucial for understanding and developing advanced materials for many engineering applications as well as for understanding natural materials. In recent decades, atom probe tomography (APT), which combines a point projection microscope and time-of-flight mass spectrometer, has evolved to be an excellent characterisation technique capable of providing 3-D nanoscale characterisation of materials with sub-nanometer scale spatial resolution, with equal sensitivity for all elements. This review discusses the current state, as of APT instrumentation, new developments in sample preparation methods, experimental procedures for different material classes, reconstruction of APT results, the current status of correlative microscopy, and application of APT for microstructural characterisation in established scientific areas like structural materials as well as new applications in semiconducting nanowires, semiconductor devices, battery materials, catalyst materials, geological materials, and biological materials. Finally, a brief perspective is given regarding the future of APT. [ABSTRACT FROM AUTHOR]

This paper develops a detailed analysis of reaction–diffusion processes within a porous rhodium-alumina catalyst washcoat. Focused-ion-beam–scanning-electron-microscope (FIB–SEM) techniques are developed and applied to reconstruct the actual catalyst-support microstructure. Three-dimensional transport processes within washcoat micro-pore structures are modeled using a dimensionless representation of reaction and diffusion rates based on the Damköhler number. Three-dimensional computational solutions for particular porous microstructures are modeled and interpreted. In a companion paper, these microstructural results are used to assist development of larger-scale models that can be incorporated into reactor-scale simulations. [ABSTRACT FROM AUTHOR]

This paper first develops a two-dimensional Thiele-type cylindrical-pore model that predicts catalytic washcoat performance, albeit for idealized cylindrical pores. The primary purpose for the cylindrical-pore model is to serve as a basis of comparison with three-dimensional models of catalytic performance in actual geometrically complex washcoat pores that are tomographically reconstructed from focused-ion-beam–scanning-electron-microscopy (FIB–SEM) measurements. In both models, the reaction–diffusion processes are characterized by a Damköhler number that is based on a pore diffusion coefficient and a single first-order reaction rate. Performance metrics include effective product flux from the pores, pore effectiveness, and reaction depth within the pore. In all cases, the models are generalized by casting the conservation equations and performance metrics as dimensionless variables. The paper then derives expressions to upscale individual pore performance to full-scale washcoats. The new understanding that emerges from these studies provides qualitative and quantitative insight that can assist the design and fabrication of improved washcoat microstructures. [ABSTRACT FROM AUTHOR]

The use of ZnTe buffer layers at the back contact of CdTe solar cells has been credited with contributing to recent improvements in both champion cell efficiency and module stability. To better understand the controlling physical and chemical phenomena, high resolution transmission electron microscopy (HR-TEM) and atom probe tomography (APT) were used to study the evolution of the back contact region during rapid thermal processing (RTP) of this layer. After activation the ZnTe layer, initially nanocrystalline and homogenous, transforms into a bilayer structure consisting of a disordered region in contact with CdTe characterized by significant Cd–Zn interdiffusion, and a nanocrystalline layer that shows evidence of grain growth and twin formation. Copper, co-evaporated uniformly within ZnTe, is found to dramatically segregate and aggregate after RTP, either collecting near the ZnTe|Au interface or forming Cu x Te clusters in the CdTe layer at defects or grain boundaries near the interface. Analysis of TEM images revealed that Zn accumulates at the edge of these clusters, and three-dimensional APT images confirmed that these are core–shell nanostructures consisting of Cu 1.4 Te clusters encased in Zn. These changes in morphology and composition are related to cell performance and stability. [ABSTRACT FROM AUTHOR]

Front/back poly-Si/SiO 2 contact devices suffer from low short-circuit current density, J sc , due to parasitic optical absorption in the front poly-Si layer. Thin poly-Si (~20 nm) allows for high J sc but is not compatible with screen-printed fire-through contacts. We therefore study the effects of post-deposition etching of a thick poly-Si (200 nm) front layer by reactive ion etching (RIE) using the metal grid lines as a self-aligned mask. We show that passivation is maintained in the device during RIE and that J sc is increased by a gain in the blue quantum efficiency response. However, our specific etching parameters cause non-uniform etching of the poly-Si leading to premature loss of passivation without optimal gain in J sc. Etched, unpassivated layers can be re-passivated with a H-containing dielectric layer leading to a gain in J sc , open circuit voltage, V oc , Fill-Factor, FF, and efficiency. Image 1 • Reactive Ion Etching of poly-Si/SiO 2 contacts on silicon solar cells thins poly-Si while preserving passivation. • Metal grid lines function as RIE masks to preserve poly-Si during RIE. • Selective area etching allows thick poly-Si under metal grid lines and thin poly-Si elsewhere, increasing J sc. • Under certain RIE conditions passivation is lost before the entire poly-Si layer is removed. • Passivation can be restored with a post-RIE dielectric layer deposition and anneal. [ABSTRACT FROM AUTHOR]

• Electrostatic effects degrade the quality of mass spectra for electrically insulating samples in straight-flight-path atom probe microscopes. • A parameter-free 'systematic energy deficit' correction was developed to correct for the electrostatic effects. • The 'systematic energy deficit' correction significantly improves the quality of CeO 2 and SiO 2 mass spectra. Improvements in the mass resolution of a mass spectrometer directly correlate to improvements in peak identification and quantification. Here, we describe a post-processing technique developed to increase the quality of mass spectra of strongly insulating samples in laser-pulsed atom probe microscopy. The technique leverages the self-similarity of atom probe mass spectra collected at different times during an experimental run to correct for electrostatic artifacts that present as systematic energy deficits. We demonstrate the method on fused silica (SiO 2) and neodymium-doped ceria (CeO 2) samples which highlight the improvements that can be made to the mass spectrum of strongly insulating samples. [ABSTRACT FROM AUTHOR]

• Crystal orientation can be determined on the nanoscale in a scanning transmission electron microscope (STEM) by scanning a probe across the sample and collecting Kikuchi diffraction patterns at each position. • Commercially available software for the widely used electron backscatter diffraction (EBSD) technique is capable of image processing, indexing and analyzing individual STEM Kikuchi patterns and maps of patterns. • Orientation resolution of the technique was found to be 0.15°, while <25 nm features could be spatially resolved. • The Kikuchi mapping technique successfully and reliably determined the phases and crystal orientations in three different samples: titanium, steel, and an oxide. Relating a crystal's microscopic structure—such as orientation and size—to a material's macroscopic properties is of great importance in materials science. Although most crystal orientation microscopy is performed in the scanning electron microscope (SEM), transmission electron microscopy (TEM)-based methods have a number of benefits, including higher spatial resolution. Current TEM orientation methods have either specific hardware requirements or use software that has limited scope, utility, or availability. In this article, a technique is described for orientation mapping using Kikuchi diffraction patterns generated from a focused STEM probe. One key advantage is that indexing and analysis of the patterns and maps occurs in the robust OIM Analysis software, currently widely used for electron backscatter diffraction (EBSD) and transmission Kikuchi diffraction (TKD) analysis. It was found that with minimal to no image processing and by changing only a few software parameters, reliable indexing of Kikuchi patterns is possible. Three samples, a deformed β-Titanium (Ti), a medium carbon heat-treated steel, and BaCe 0.8 Y 0.2 O 3-δ were tested to determine the effectiveness of the approach. In all three measurements the algorithms effectively and reliably determined the phases and the crystal orientations of the features measured. For the two orientation maps produced, less than 5% of the patterns were misindexed including boundary areas where overlapping patterns existed. An angular resolution of 0.15° was achieved while features <25 nm were able to be spatially resolved. [ABSTRACT FROM AUTHOR]

Despite their high relative abundance in our Universe, neutrinos are the least understood fundamental particles of nature. In fact, the quantum properties of neutrinos emitted in experimentally relevant sources are theoretically contested 1-4 and the spatial extent of the neutrino wavepacket is only loosely constrained by reactor neutrino oscillation data with a spread of 13 orders of magnitude 5,6 . Here we present a method to directly access this quantity by precisely measuring the energy width of the recoil daughter nucleus emitted in the radioactive decay of beryllium-7. The final state in the decay process contains a recoiling lithium-7 nucleus, which is entangled with an electron neutrino at creation. The lithium-7 energy spectrum is measured to high precision by directly embedding beryllium-7 radioisotopes into a high-resolution superconducting tunnel junction that is operated as a cryogenic sensor. Under this approach, we set a lower limit on the Heisenberg spatial uncertainty of the recoil daughter of 6.2 pm, which implies that the final-state system is localized at a scale more than a thousand times larger than the nucleus itself. From this measurement, the first, to our knowledge, direct lower limit on the spatial extent of a neutrino wavepacket is extracted. These results may have implications in several areas including the theoretical understanding of neutrino properties, the nature of localization in weak nuclear decays and the interpretation of neutrino physics data., Competing Interests: Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Protonic ceramic electrochemical cells (PCECs) can operate at intermediate temperatures (450° to 600°C) for power generation and hydrogen production. However, the operating temperature is still too high to revolutionize ceramic electrochemical cell technology. Lowering the operating temperature to <450°C will enable a wider material choice and reduce system costs. We present approaches to redesigning PCECs via readily fabricated single-grain-thick, chemically homogeneous, and robust electrolytes and a nano-micro positive electrode. At 450°C, the PCECs achieve a peak power density of 1.6 watt per square centimeter on H 2 fuel, 0.5 watt per square centimeter on NH 3 fuel, and 0.3 watt per square centimeter on CH 4 fuel in fuel cell mode. In steam electrolysis mode, a current density of >0.6 ampere per square centimeter with a Faradaic efficiency of >90% is achievable at 1.4 volt and 400°C. In addition, exceptional durability (>2000 hours) has been demonstrated, with a degradation rate of <0.01 millivolt per 100 hours in fuel cell mode at 400°C.

CH 4 -fueled metal-supported solid oxide fuel cells (CH 4 -MS-SOFCs) are propitious as CH 4 is low-priced and readily available, and its renewable production is possible, such as biomethane. However, the current CH 4 -MS-SOFCs suffer from either poor power density or short durable operation, which is ascribed to the low catalytic activity and poor coking tolerance of the metallic anode support. Herein, we have deliberately designed and synthesized a highly active nanocomposite catalyst, Sm-doped CeO 2 -supported Ni, as the internal steam methane reforming catalyst, to optimize CH 4 -MS-SOFCs. Both power densities and durability of optimized CH 4 -MS-SOFCs have been dramatically enhanced compared to the pristine CH 4 -MS-SOFCs. The optimized CH 4 -MS-SOFCs deliver the highest performances among all zirconia-based CH 4 -MS-SOFCs. Furthermore, the operating temperature has been reduced to 600 °C. At 600 °C, a viable peak power density of >350 mW/cm 2 is achieved, which is more than three times as high as the pristine CH 4 -MS-SOFCs. Furthermore, the optimized CH 4 -MS-SOFC achieves >1000 h of stable operation.

Highly active and selective CO 2 methanation catalysts are critical to CO 2 upgrading, synthetic natural gas production, and CO 2 emission reduction. Wet impregnation is widely used to synthesize oxide-supported metallic nanoparticles as the catalyst for CO 2 methanation. However, as the reagents cannot be homogeneously mixed at an atomic level, it is challenging to modulate the microstructure, crystal structure, chemical composition, and electronic structure of catalysts via wet impregnation. Herein, a scalable and straightforward catalyst fabrication approach has been designed and validated to produce Sm 0.25 Ce 0.75 O 2-δ -supported Ni (SDC-Ni) as the CO 2 methanation catalyst. By varying the chelating agents-to-total metal cations ratio ( C / I ratio) during the catalyst synthesis, we can readily and simultaneously modulate the microstructure, metallic surface area, crystal structure, chemical composition, and electronic structure of SDC-Ni, consequently fine-tuning the oxide-support interactions and CO 2 methanation activity. The optimal C / I ratio (0.1) leads to an SDC-Ni catalyst that facilitates C-O bond cleavage and significantly improves CO 2 conversion at 250 °C. A CO 2 -to-CH 4 yield of >73% has been achieved at 250 °C. Furthermore, a stable operation of >1500 hours has been demonstrated, and no degradation is observed. Extensive characterizations were performed to fundamentally understand how to tune and enhance CO 2 methanation activity of SDC-Ni by modulating the C / I ratio. The correlation of physical, chemical, and catalytic properties of SDC-Ni with the C / I ratio is established and thoroughly elaborated in this work. This study could be applied to tune the oxide-support interactions of various catalysts for enhancing the catalytic activity.

Pulsed coherent extreme ultraviolet (EUV) radiation is a potential alternative to pulsed near-ultraviolet (NUV) wavelengths for atom probe tomography. EUV radiation has the benefit of high absorption within the first few nm of the sample surface for elements across the entire periodic table. In addition, EUV radiation may also offer athermal field ion emission pathways through direct photoionization or core-hole Auger decay processes, which are not possible with the (much lower) photon energies used in conventional NUV laser-pulsed atom probe. We report preliminary results from what we believe to be the world's first EUV radiation-pulsed atom probe microscope. The instrument consists of a femtosecond-pulsed, coherent EUV radiation source interfaced to a local electrode atom probe tomograph by means of a vacuum manifold beamline. EUV photon-assisted field ion emission (of substrate atoms) has been demonstrated on various insulating, semiconducting, and metallic specimens. Select examples are shown.

Atom probe tomography reconstructions provide valuable information on nanometer-scale compositional variations within materials. As such, the spatial accuracy of the reconstructions is of primary importance for the resulting conclusions to be valid. Here, the use of transmission electron microscopy images before and after atom probe analysis to provide additional information and constraints is examined for a number of different materials. In particular, the consistency between the input reconstruction parameters and the output reconstruction is explored. It is demonstrated that it is possible to generate reconstructions in which the input and known values are completely consistent with the output reconstructions. Yet, it is also found that for all of the datasets examined, a particular power law relationship exists such that, if the image compression factor or detection efficiency is not constrained, a series of similarly spatially accurate reconstructions results. However, if one of these values can be independently assessed, then the other is known as well. Means of incorporating these findings and this general methodology into reconstruction protocols are also discussed., (Copyright © 2018. Published by Elsevier B.V.)

The relative chemistry from grain interiors to grain boundaries help explain why grain boundaries may be beneficial, detrimental or benign towards device performance. 3D Nanoscale chemical analysis extracted from atom probe tomography (APT) (10's of parts-per-million chemical sensitivity and sub-nanometer spatial resolution) of twenty grain boundaries in a high-efficiency Cu(In, Ga)Se 2 solar cell shows the matrix and alkali concentrations are wide-ranging. The concentration profiles are then related to band structure which provide a unique insight into grain boundary electrical performance. Fluctuating Cu, In and Ga concentrations result in a wide distribution of potential barriers at the valence band maximum (VBM) (-10 to -160 meV) and the conduction band minimum (CBM) (-20 to -70 meV). Furthermore, Na and K segregation is not correlated to hampering donors, (In, Ga) Cu and V Se , contrary to what has been previously reported. In addition, Na and K are predicted to be n-type dopants at grain boundaries. An overall band structure at grain boundaries is presented.

There are approximately 1.5 million people who experience traumatic injuries to the brain and 265,000 who experience traumatic injuries to the spinal cord each year in the United States. Currently, there are few effective treatments for central nervous system (CNS) injuries because the CNS is refractory to axonal regeneration and relatively inaccessible to many pharmacological treatments. Smart, remotely tunable, multifunctional micro- and nanocarriers hold promise for delivering treatments to the CNS and targeting specific neurons to enhance axon regeneration and synaptogenesis. Furthermore, assessing the efficacy of treatments could be enhanced by biocompatible nanovectors designed for imaging in vivo. Recent developments in nanoengineering offer promising alternatives for designing biocompatible micro- and nanovectors, including magnetic nanostructures, carbon nanotubes, and quantum dot-based systems for controlled release of therapeutic and diagnostic agents to targeted CNS cells. This review highlights recent achievements in the development of smart nanostructures to overcome the existing challenges for treating CNS injuries., (Copyright © 2012 Elsevier B.V. All rights reserved.)