TEM sample preparation of microsized LiMn2O4 powder using an ion slicer

The main purpose of this paper is the preparation of transmission electron microscopy (TEM) samples from the microsized powders of lithium-ion secondary batteries. To avoid artefacts during TEM sample preparation, the use of ion slicer milling for thinning and maintaining the intrinsic structure is described. Argon-ion milling techniques have been widely examined to make optimal specimens, thereby making TEM analysis more reliable. In the past few years, the correction of spherical aberration (Cs) in scanning transmission electron microscopy (STEM) has been developing rapidly, which results in direct observation at an atomic level resolution not only at a high acceleration voltage but also at a deaccelerated voltage. In particular, low-kV application has markedly increased, which requires a sufficiently transparent specimen without structural distortion during the sample preparation process. In this study, sample preparation for high-resolution STEM observation is accomplished, and investigations on the crystal integrity are carried out by Cs-corrected STEM.

The effects of ion implantation damage to photonic crystal optomechanical resonators in silicon

Optomechanical resonators were fabricated on a silicon-on-insulator (SOI) substrate that had been implanted with phosphorus donors. The resonators’ mechanical and optical properties were then measured (at 6 kelvin and room temperature) before and after the substrate was annealed. All measured resonators survived the annealing and their mechanical linewidths decreased while their optical and mechanical frequencies increased. This is consistent with crystal lattice damage from the ion implantation causing the optical and mechanical properties to degrade and then subsequently being repaired by the annealing. We explain these effects qualitatively with changes in the silicon crystal lattice structure. We also report on some unexplained features in the pre-anneal samples. In addition, we report partial fabrication of optomechanical resonators with neon ion milling.

Nanopatterning of oxide 2-dimensional electron systems using low-temperature ion milling

We present a "top-down" patterning technique based on ion milling performed at low- temperature, for the realization of oxide two-dimensional electron system (2DES) devices with dimensions down to 160 nm. Using electrical transport and scanning SQUID measurements we demonstrate that the low-temperature ion milling process does not damage the 2DES properties nor creates oxygen vacancies-related conducting paths in the STO substrate. As opposed to other procedures used to realize oxide 2DES devices, the one we propose gives lateral access to the 2DES along the in-plane directions, finally opening the way to coupling with other materials, including superconductors.

Accurate Sub-micron Device Delayering of Plan View TEM Specimens By Ar Ion Milling

With the introduction of new materials, new device structures, and shrinking device dimensions, failure mechanisms evolve, which can make identifying defects challenging. Therefore, an accurate and controllable delayering process to target defects is desirable. We present a workflow comprised of bulk device delayering by broad Ar ion beam milling, plan view specimen preparation by focused ion beam tool, followed by site-specific delayering by concentrated Ar ion beam milling. The result is an accurately delayered device, without sample preparation-induced artifacts, that is suitable for uncovering defects during physical failure analysis.

Exploring the Infiltration Features of Perovskite within Mesoporous Carbon Stack Solar Cells Using Broad Beam Ion Milling

Carbon perovskite solar cells (C-PSCs) are a popular photovoltaic technology currently undergoing extensive development on the global research scene. Whilst their record efficiency now rivals that of silicon PV in small-scale devices, C-PSCs still require considerable development to progress to a commercial-scale product. This study is the first of its kind to use broad beam ion milling for C-PSCs. It investigates how the carbon ink, usually optimised for maximum sheet conductivity, impacts the infiltration of the perovskite into the active layers, which in turn impacts the performance of the cells. Through the use of secondary electron microscopy with energy-dispersive X-ray spectroscopy, infiltration defects were revealed relating to carbon flake orientation. The cross sections imaged showed between a 2% and 100% inactive area within the C-PSCs due to this carbon blocking effect. The impact of these defects on the performance of solar cells is considerable, and by better understanding these defects devices can be improved for mass manufacture.

Manuscript Title: Mechanical and Microstructural Studies of Volcanic Ash Beds in Unconventional Reservoirs

Volcanic ash beds are thin layers commonly observed in the Eagle Ford, Niobrara and, Vaca Muerta formations. Because of their differences in composition, sedimentary structures, and diagenetic alteration, they exhibit a significant contrast in mechanical properties with respect to surrounding formation layers. This can impact hydraulic fracturing, affecting fracture propagation and fracture geometry. Quantifying the mechanical properties of ash beds becomes significant; however, it is a challenge with traditional testing methods. Common logging fails to identify the ash beds, and core plug testing is not possible because of their friability. In this study, nanoindentation was used to measure the mechanical properties (Young's modulus, creep, and anisotropy) in Eagle Ford ash beds, and to determine the contrast with the formation matrix properties. Two separate ash beds of high clay and plagioclase composition were epoxied in an aluminum tray and left for 48 hours curing time. Horizontal and vertical samples of ash beds were acquired and mounted on a metal stub, followed by polishing and broad beam ion milling. Adjacent samples were also prepared for high-resolution Scanning Electron Microscope (SEM) microstructural analysis. The Young's modulus in ash beds ranged from 12 to 24 GPa, with the horizontal direction Young's modulus being slightly greater than that of the vertical samples. The Young's modulus contrast with adjacent layers was calculated to be 1:2 with clay-rich zones and 1:4 with calcite rich zones. The creep deformation rate was three times higher for ash beds compared to other zones. Using Backus averaging, it was determined that the presence of ash beds can increase the anisotropy in the formation by 15-25%. SEM results showed a variation in microstructure between the ash beds with evidence of diagenetic conversion of rhyolitic material into clays. Key differences between the two ash beds were due to the presence of plagioclase and the occurrence of porosity within kaolinite. Overall porosity varied between the two ash beds and adjacent carbonate layers showing a significant increase in porosity. Understanding the moduli contrast between adjacent layers can improve the hydraulic fracturing design when ash beds are encountered. In addition, the presence of these beds can lead to proppant embedment and loss in fracture connectivity. These results can be used for improving geomechanical models.

TEM sample preparation for Li-ion secondary battery using ion slicer

The main purpose in this paper is a sample preparation of transmission electron microscopy (TEM) for the lithium-ion secondary battery in the form of micro-sized powders. To avoid artefacts of the TEM sample preparation, the use of ion slicer milling for thinning and maintaining the intrinsic structure is described. Argon-ion milling techniques have been widely examined to make the optimized specimen, which makes TEM analysis more reliable. In the past few years, the correction of spherical aberration (Cs) in scanning transmission electron microscopy (STEM) has been developing rapidly, that results in the direct observation with the atomic level resolution not only for the high acceleration voltage but also its deaccelerated voltage as well. Especially, low-kV application has been markedly increased that needs the sufficient-transparent specimen without the structural distortion during the process of the sample preparation. In this study, the sample preparation for the high-resolution STEM observation has been greatly accomplished and investigations of its crystal integrity are carried out by Cs-corrected STEM.

Mechanical and Compositional Implications of Gallium Ion Milling on Epoxy Resin

Focused Ion Beam (FIB) is one of the most common methods for nanodevice fabrication. However, its implications on mechanical properties of polymers have only been speculated. In the current study, we demonstrated flexural bending of FIB-milled epoxy nanobeam, examined in situ under a transmission electron microscope (TEM). Controllable displacement was applied, while real-time TEM videos were gathered to produce morphological data. EDS and EELS were used to characterize the compositions of the resultant structure, and a computational model was used, together with the quantitative results of the in situ bending, to mechanically characterize the effect of Ga+ ions irradiation. The damaged layer was measured at 30 nm, with high content of gallium (40%). Examination of the fracture revealed crack propagation within the elastic region and rapid crack growth up to fracture, attesting to enhanced brittleness. Importantly, the nanoscale epoxy exhibited a robust increase in flexural strength, associated with chemical tempering and ion-induced peening effects, stiffening the outer surface. Young’s modulus of the stiffened layer was calculated via the finite element analysis (FEA) simulation, according to the measurement of 30 nm thickness in the STEM and resulted in a modulus range of 30–100 GPa. The current findings, now established in direct measurements, pave the way to improved applications of polymers in nanoscale devices to include soft materials, such as polymer-based composites and biological samples.