Focused Ion Beam Lift-out Technique Research Articles

Electron Microscopy Investigation of Porous Transport Layer Coatings

The flow of reactants and biproducts to and from the anode in polymer electrolyte membrane (PEM) water electrolyzers is dictated by the properties of the porous transport layer (PTL). The PTL is made of titanium (Ti) fibers or sintered particles to provide stable thermal and electronic conduction pathways at the high overpotentials and acid conditions experienced at the anode. To prevent the formation of a thick native oxide on the Ti PTL surface, precious metal coatings are required. These coatings enable and maintain a reduced interfacial resistance between the PTL and catalyst layer. Understanding the impact of surface treatments and coatings on the morphology and composition of this interface is an important step to minimizing interfacial resistance, degradation and production costs. In this work, ion and electron beam techniques, including focused ion beam (FIB), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and scanning transmission electron microscopy (STEM), are used to investigate PTL coatings at the nanoscale.A series of fiber-type PTLs with a range of platinum (Pt) coating thicknesses were synthesized using physical vapor deposition. The uniformity of the coatings was analyzed using SEM-EDS in both plan-view and cross-section. Sections of individual fibers were then removed using FIB lift-out technique and thinned to less than 50 nanometers for further analysis by STEM. The thickness and uniformity of the Pt coating was quantified from STEM images for each Pt loading and correlated with interfacial resistance measurements. Changes to the thickness and composition of the coatings and oxide layers after single cell tests will also be reported alongside additional insights from correlative characterization approaches like atomic force microscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. Overall, these findings will help steer the development of PTL treatments and coatings for highly durable and efficient PEM water electrolyzers towards meeting the U.S. Department of Energy’s Hydrogen Shot to reduce the cost of clean hydrogen production to $1 per kg by 2031.Funding for this work was provided by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office through the H2NEW Consortium. Electron microscopy research conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory.

Enhanced oxidation resistance of Ce by addition of Ga and nanocrystallization

Ce is prone to catastrophic oxidation at room temperature and its oxidation resistance is difficult to be improved by alloying. Herein, we found that the oxidation resistance of active metal Ce can be significantly improved by the addition of 20 at.% Ga. Focused ion beam lift-out technique and scanning transmission electron microscopy analysis disclosed that a discontinuous Ga-rich layer was generated beneath the oxide layer in the coarse-grained Ce-Ga alloy. The Ga-rich layer formed by selective oxidation of Ce acts as a diffusion barrier for Ce outward diffusion and ceases the O/M interfacial reaction when a critical concentration of Ga (75 at.%) is reached. After nanocrystallization, uniform distribution of Ga was achieved. After oxidation, a relatively continuous Ga-rich layer was formed which further enhanced the oxidation resistance. The introduction of noble elements combining with nanocrystallization may provide a novel strategy for the protection of metals with high activity and poor oxidation resistance.

Size-induced twinning in InSb semiconductor during room temperature deformation

Room-temperature deformation mechanism of InSb micro-pillars has been investigated via a multi-scale experimental approach, where micro-pillars of 2 µm and 5 µm in diameter were first fabricated by focused ion beam (FIB) milling and in situ deformed in the FIB-SEM by micro-compression using a nano-indenter equipped with a flat tip. Strain rate jumps have been performed to determine the strain rate sensitivity coefficient and the related activation volume. The activation volume is found to be of the order of 3–5 b3, considering that plasticity is mediated by Shockley partial dislocations. Transmission electron microscopy (TEM) thin foils were extracted from deformed micro-pillars via the FIB lift-out technique: TEM analysis reveals the presence of nano-twins as major mechanism of plastic deformation, involving Shockley partial dislocations. The presence of twins was never reported in previous studies on the plasticity of bulk InSb: this deformation mechanism is discussed in the context of the plasticity of small-scale samples.

Resolving Iron(II) Sorption and Oxidative Growth on Hematite (001) Using Atom Probe Tomography

The distribution of Fe resulting from the autocatalytic interaction of aqueous Fe(II) with the hematite (α-Fe2O3) (001) surface was directly mapped in three dimensions (3D) for the first time, using Fe isotopic labeling and atom probe tomography (APT). Micrometer-sized hematite platelets were reacted with aqueous Fe(II) enriched in 57Fe and prepared for APT using conventional focused ion beam lift-out techniques. Mass spectrum analyses show that specific Fe-ionic species (i.e., Fe2+ and FeO+) accurately reproduce isotopic ratios within natural abundance in the hematite bulk, and thus were utilized to characterize the distribution of 57Fe and quantify Fe isotopic concentrations. 3D reconstructions of Fe isotopic positions along the surface normal direction showed a zone enriched in 57Fe, consistent with oxidative adsorption of Fe(II) and growth at the relict hematite surface reacted with 57Fe(II)aq. An average net adsorption of 3.2–4.3 57Fe atoms nm–2 was estimated using Gibbsian interfacial excess princip...

Identification of the Zirconia Phases by Means of Raman Spectroscopy for Specimens Prepared by FIB Lift-Out Technique

The zirconium–zirconia interface that developed during high-temperature corrosion of pure zirconium was investigated. Samples were oxidized at 600 °C in air at atmospheric pressure. The oxidized sample was then prepared by means of focused ion beam (FIB) lift-out technique and examined using Raman spectroscopy technique in three different oxide zones (external, internal, and close to the metal–oxide interface). Structural investigation was performed using line mode Raman analysis. Implementation of these techniques revealed complexity of the studied system and confirmed the presence of a thin tetragonal sub-layer located in the proximity of the metal. Recorded Raman band displacements of monoclinic and tetragonal phases were interpreted in terms of stoichiometry level and compressive stress in the oxide. The thin layer of tetragonal phase is most likely characterized by lower amount of oxygen than the external part of the oxide.

Nanoscale variations in 187 Os isotopic composition and HSE systematics in a Bultfontein peridotite

Abstract Understanding the mineralogical controls on radiogenic chronometers is a fundamental aspect of all geochronological tools. As with other common dating tools, it has become increasingly clear that the Re–Os system can be impacted by multiple mineral formation events. The accessory and micrometric nature of the Re–Os-bearing minerals has made assessing this influence complex. This is especially evident in cratonic peridotites, where long residence times and multiple metasomatic events have created a complex melting and re-enrichment history. Here we investigate a harzburgitic peridotite from the Bultfontein kimberlite (South Africa) which contains sub-micron Pt–Fe-alloy inclusions within base metal sulphides (BMS). Through the combination of the focused ion beam lift-out technique and low blank mass spectrometry we were able to remove and analyse the Pt–Fe-alloy inclusions for their Re–Os composition and highly siderophile element (HSE) systematics. Six repeats of the whole-rock yield 187 Os/ 188 Os compositions of 0.10893–0.10965, which correspond to Re depletion model ages (T RD ) of 2.69–2.79 Ga. The Os, Ir and Pt concentrations are slightly variable across the different digestions, whilst Pd and Re remain constant. The resulting HSE pattern is typical of cratonic peridotites displaying depleted Pt and Pd. The Pt–Fe-alloys have PUM-like 187 Os/ 188 Os compositions of 0.1294 ± 24 (2-s.d.) and 0.1342 ± 38 , and exhibit a saw-tooth HSE pattern with enriched Re and Pt. In contrast, their BMS hosts have unradiogenic 187 Os/ 188 Os of 0.1084 ± 6 and 0.1066 ± 3 , with T RD ages of 2.86 and 3.09 Ga, similar to the whole-rock systematics. The metasomatic origin of the BMS is supported by (i) the highly depleted nature of the mantle peridotite and (ii) their Ni-rich sulphide assemblage. Occurrence of Pt–Fe-alloys as inclusions within BMS grains demonstrates the genetic link between the BMS and Pt–Fe-alloys and argues for formation during a single but continuous event of silicate melt percolation. While the high solubility of HSE within sulphide mattes rules out early formation of the alloys from a S-undersaturated silicate melt and subsequent scavenging in a sulphide matte, the alignment of the Pt–Fe-alloy inclusions attests that they are exsolutions formed during the sub-solidus re-equilibration of the high temperature sulphide phases. The significant difference in 187 Os/ 188 Os composition between the included Pt–Fe-alloys and their BMS host can only be accounted for by different Re/Os. This suggests that the formation of Pt–Fe-alloy inclusions within a BMS can result in the fractionation of Re from Os. A survey experiment examining the partitioning of Re and Os confirmed this observation, with the Re/Os of the Pt–Fe-alloy inclusion up to ten times higher than the co-existing BMS. This fractionation implies that, when Re is present in the sulphide melt, the T RD ages of BMS containing alloy inclusions do not date the loss of Re due to partial melting, but rather its fractionation into the Pt–Fe-alloys. As such, BMS ages should be used with caution when dating ancient partial melting events.

Specimen Preparation Method to Dual-Axis TEM Analysis Technique

We usually do Physical Failure Analysis (PFA) to visualize the failure in the semiconductor process. First, we find the site-specific target (or failed cell). And then, we should do de-processing which contains lapping and chemical etch. As the semiconductor gets more complex and multi-layer, we should do multi-de-processing steps. If the failure has the oxide-material, we cannot know the cause of failure. Because the oxide can be removed by Hydrogen Fluoride (HF) chemical, which means the failure will be gone during de-processing step. We should use Focused Ion Beam (FIB) which can make a thin sample to exclude chemical step. High-resolution analytical tools such as Transmission Electron Microscopy (TEM) have become indispensable in PFA. We make a Dual-Axis TEM (DAT) method for PFA. We make a Plan-view TEM (PTEM) sample with FIB first, we can find an exact location of failure through the first step. And then, we make cross-sectional TEM (XTEM) sample with a site-specific target in PTEM sample. Below summarizes the four major steps and its precautions;1. Making a Planar lamella by FIB2. Observing a PTEM specimen with TEM(Precaution : zone axis should be adjusted exactly)3. Making a cross-section lamella by FIB(Precaution : Protection layer should be deposited on both sides)4. Observing a XTEM specimen with TEMWe propose DAT method to improve the problem of artifact in de-processing step. The TEM result with DAT method is shown in figure 4. We can know the exact location of failure with observing a PTEM sample. We can know the cause of failure with observing a XTEM sample. Moreover, we can analysis the chemical and physical information through DAT method. This method is very effective and has a high success rate in analysis. REFERENCE [1] A.E.M. De Veirman, “3-Dimensional’ TEM silicon-device analysis by combining plan-view and FIB sample preparation”, Materials Science and Engineering: B, 102(1-3), pp. 63-69, 2003. [2] Jon C. Lee, David Su, J.H. Chuang, “A Novel Application of the FIB Lift-out Technique for 3-D TEM Analysis”, Microelectronics Reliability Asset, 41(9-11), pp. 1551-1556, 2001. Figure 1

Preparation of high‐quality ultrathin transmission electron microscopy specimens of a nanocrystalline metallic powder

This article explores the achievable transmission electron microscopy specimen thickness and quality by using three different preparation methods in the case of a high-strength nanocrystalline Cu-Nb powder alloy. Low specimen thickness is essential for spatially resolved analyses of the grains in nanocrystalline materials. We have found that single-sided as well as double-sided low-angle Ar ion milling of the Cu-Nb powders embedded into epoxy resin produced wedge-shaped particles of very low thickness (<10 nm) near the edge. By means of a modified focused ion beam lift-out technique generating holes in the lamella interior large micrometer-sized electron-transparent regions were obtained. However, this lamella displayed a higher thickness at the rim of ≥30 nm. Limiting factors for the observed thicknesses are discussed including ion damage depths, backscattering, and surface roughness, which depend on ion type, energy, current density, and specimen motion. Finally, sections cut by ultramicrotomy at low stroke rate and low set thickness offered vast, several tens of square micrometers uniformly thin regions of ∼10-nm minimum thickness. As major drawbacks, we have detected a thin coating on the sections consisting of epoxy deployed as the embedding material and considerable nanoscale thickness variations.

Ni–Au core–shell nanowires: synthesis, microstructures, biofunctionalization, and the toxicological effects on pancreatic cancer cells

The nickel (Ni)–gold (Au) core–shell nanowires (CSNWs) were synthesized by a combination of electrodeposition and electroless-plating methods. This template based, electroless-plating approach can control the size and shape of nanostructures by adjusting the experimental conditions. The X-ray diffraction, transmission electron microscopy (TEM), and TEM line-scanning and elemental mapping analyses were applied to investigate the formation and microstructure of the core–shell nanostructure. Also using a focused ion beam lift-out technique provides an important route to prove the inner microstructural details of the CSNWs. The optical characterization showed the surface plasmon absorption shifting with electroless-plating time, whereas the magnetic measurements revealed the shape anisotropy and soft ferromagnetic properties of the NWs. Using the strong interaction between biotin and streptavidin, streptavidin–fluorescent dyes were successfully conjugated on the biotinylated CSNWs. This was then analyzed for the surface plasmon resonance effect and Stokes' shifting viaultraviolet-visible and photoluminescence spectroscopy measurements and imaged by confocal scanning laser microscopy. Proliferating cancer cells (Panc-1) have been used to study the toxicological effects of both Ni–Au CSNWs and Ni NWs in a living cell system: the cellular responses to nanowire effects were observed. Ni–Au CSNWs appeared to be tolerated more by this cell line at the dose tested than Ni NWs.

TEM Characterization of As-Deposited and Annealed Ni/Al Multilayer Thin Film

Reactive multilayer thin films that undergo highly exothermic reactions are attractive choices for applications in ignition, propulsion, and joining systems. Ni/Al reactive multilayer thin films were deposited by dc magnetron sputtering with a period of 14 nm. The microstructure of the as-deposited and heat-treated Ni/Al multilayers was studied by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) in plan view and in cross section. The cross-section samples for TEM and STEM were prepared by focused ion beam lift-out technique. TEM analysis indicates that the as-deposited samples were composed of Ni and Al. High-resolution TEM images reveal the presence of NiAl in small localized regions. Microstructural characterization shows that heat treating at 450 and 700°C transforms the Ni/Al multilayered structure into equiaxed NiAl fine grains.

3D reconstruction of SOFC anodes using a focused ion beam lift-out technique

Improvements to electrode performance are essential to accelerate the commercialisation of SOFC technology. A key metric of performance for SOFC electrodes is the length and distribution of three or triple phase boundaries (TPBs) which provide an indication of electrochemical performance. Techniques that can be used to characterise TPB length are highly valuable; with an increasing knowledge of electrode microstructures, electrochemical performance can be optimised. One such technique for electrode characterisation uses focused ion beams (FIB) to sequentially mill and image an electrode surface, obtaining a sequence of 2D images that may be reconstructed in a 3D space. In this paper we present a technique to maximise the quality of the raw data obtained via ex-situ characterisation of electrode micro-sections based on FIB lift-out. With improved raw data, we have been able to conduct semi-automated image analysis to extract key microstructural information, including the length and distribution of TPBs. Reconstructions have been carried out using both single and dual beam instruments; two reconstructions of Ni–YSZ anode structures are presented here.

Preparation of location-specific thin foils from Fe–3% Si bi- and tri-crystals for examination in a FEG-STEM

Bi-crystals and tri-crystals of a nominal Fe–3% Si (wt%) of well-defined orientations have been grown using a floating-zone technique with optical heating. The manufacture of these unique crystals and the preparation technique involved in harvesting thin foils from specific locations for transmission electron microscopy are described in detail. In particular, the grain boundary triple junction has been extracted from the tri-crystal and examined in high-resolution aberration-corrected FEG-STEM instruments. To achieve the necessary resolution, the foils have to be uniformly thin, in the range 50–100 nm over large areas of the specimen. For ferromagnetic materials, there are further challenges arising from the magnetic field interaction, with the electron beam placing significant demands on the aberration correction system. One way to minimise this interaction is to reduce the total mass of magnetic material. To achieve this, an in situ focused ion beam lift-out technique has been combined with an additional precision ion-polishing stage to reproducibly provide thin-foil specimens suitable for high-resolution EELS and EDX analysis. Examination of the foils reveals that the final precision ion-polishing stage removes residual damage arising from the use of focused ion beam milling procedures.

FIB/DualBeam Techniques for Quantitative Analyses

Lucille A. Giannuzzi FEI Company, 5350 NE Dawson Creek Drive, Hillsboro, OR 97124 The use of Focused ion beam (FIB) and combined FIB plus scanning electron microscope (SEM) dual platform instruments have continued to increase in popularity over the past decade in both the physical and biological sciences. FIB based techniques enable site specific regions to be prepared for direct quantitative analysis and/or extracted for quantitative analyses using other analytical instruments in material systems that were once too difficult or unfeasible to observe by other means. In addition, since FIB techniques in general offer higher throughput than conventional methods, more samples may be quantified than previously possible. In this paper, quantitative techniques facilitated by either direct FIB imaging or FIB-based specimen preparation methods are discussed. One of the most popular uses of focused ion beams is for transmission electron microscopy (TEM) specimen preparation. The ubiquitous FIB lift-out techniques allow for site-specific extraction of interfaces, inclusions, failure sites, etc., from a wide range of materials [1]. Therefore, quantitative x-ray energy dispersive spectrometry (XEDS) techniques can be directly applied to e.g., interdiffusion studies [2], or grain boundary segregation effects on grain boundary diffusion [3]. A particular advantage to FIB-based imaging is the channeling contrast generated by ion induced secondary electron imaging which is unsurpassed compared to conventional SEM imaging. Thus, FIB imagining can provide direct capabilities for quantification of microstructural features. This ability to use FIB channeling contrast imaging on a mechanically polished Cu-Ni diffusion couple revealed regions where diffusion induced recrystallization (DIR) occurred at the diffusion couple interface [2]. Site specific TEM specimen preparation of DIR and non-DIR regions allowed for direct quantitative analysis of the Cu-Ni diffusion couple showing an enhancement of lattice interdiffusion due to grain boundary contributions [2]. FIB channeling across grain boundaries was also used to prepare TEM specimens for the quantification of the effects of Bi segregation on the Ni diffusion through Cu twist boundaries [3]. In addition, dopant profiles of p/n junctions within Si-based transistor gates can be quantified using electron holography methods with the utilization of back-side FIB milling plus low energy polishing steps [4]. The basic FIB lift-out techniques have also been employed to prepare samples for quantification in surface science instruments such as x-ray photoelectron spectroscopy [5], Auger electron spectroscopy [6], secondary ion mass spectroscopy (SIMS) [6], as well as 3D atom probe [7,8]. The same techniques used to prepare atom probe specimens can be used to make pillar-shaped TEM specimens for on-axis TEM tomography [9,10].

Nanoanalysis of very fine VN precipitates in steel

Abstract Core loss electron energy loss spectroscopy spectrum imaging is used to map vanadium-based precipitates with dimensions as small as 1 nm in a matrix of high strength low alloy steel. The transmission electron microscopy specimen was prepared by the focused ion beam liftout technique followed by low energy ion milling. Characterisation of such precipitates is discussed.

Combining Ar ion milling with FIB lift-out techniques to prepare high quality site-specific TEM samples.

Focused ion beam (FIB) techniques can prepare site-specific transmission electron microscopy (TEM) cross-section samples very quickly but they suffer from beam damage by the high energy Ga+ ion beam. An amorphous layer about 20-30 nm thick on each side of the TEM lamella and the supporting carbon film makes FIB-prepared samples inferior to the traditional Ar+ thinned samples for some investigations such as high resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). We have developed techniques to combine broad argon ion milling with focused ion beam lift-out methods to prepare high-quality site-specific TEM cross-section samples. Site-specific TEM cross-sections were prepared by FIB and lifted out using a Narishige micromanipulator onto a half copper-grid coated with carbon film. Pt deposition by FIB was used to bond the lamellae to the Cu grid, then the coating carbon film was removed and the sample on the bare Cu grid was polished by the usual broad beam Ar+ milling. By doing so, the thickness of the surface amorphous layers is reduced substantially and the sample quality for TEM observation is as good as the traditional Ar+ milled samples.

FIB-Zielpräparation von TEM-Proben mittels Nadelmanipulationstechnik / FIB-Pinpointed Preparation of TEM Samples by a Needle Based Manipulator (Lift-Out) Technique

The Transmission Electron Microscopy (TEM) increasingly is used to characterise the structure and morphology of microelectronic devices whose lateral dimensions steadily are diminishing. The required preparation mainly is done by the Focused Ion Beam (FIB) technology making use of its time efficient operation and well defined positioning abilities. The FlB-preparation, when applied as a needle based micromanipulator method, is called Lift-Out technique. The Lift-Out technique allows to refrain from performing any conventional preparation steps prior to the FIB preparation and because it restricts the ion beam processing additionally to a strongly minimised volume around the sample, the method reduces the preparation time significantly. Beside microelectronical applications the FIB Lift-Out technique can be applied beneficially for the pinpointed preparation on badly accessible samples as e.g. tooth materials, big steel samples, fracture surfaces of pronounced topography, hollow fibres etc.

Focused ion beam sectioning and lift-out method for copper and resist vias in organic low-k dielectrics.

The focused ion beam lift-out technique for scanning electron microscope (SEM) and transmission electron microscope (TEM) sample preparation was shown to be applicable to copper/low-k dielectric semiconductor technology. High resolution SEM, TEM, and scanning transmission electron microscope analyses were performed on metal contacts and resist vias with no evidence of the interface damage or metal smearing commonly observed with mechanical polishing. Ion milling of the sample ex situ to the substrate provided decoration and adjustment of the exposed plane of the section when necessary for SEM analysis.

Site-specific Transmission Electron Microscope Characterization of Micrometer-sized Particles Using the Focused Ion Beam Lift-out Technique.

Micrometer sized particles have been studied to show that a high-quality transmission electron microscope (TEM) specimen can be produced, without the use of embedding media, from a site-specific region of chosen particles using the focused ion beam (FIB) lift-out (LO) technique. The uniqueness of this technique is that site-specific TEM LO specimens may be obtained from particles and from regions which are smaller than the conventional approximately 10-20 &mgr;m x 5 &mgr;m x approximately 0.1 &mgr;m dimensions of the LO specimen. The innovative FIB LO procedures are described in detail and TEM images of electron transparent specimens obtained from specific micrometer-sized particles are presented.

Site-specific cross-sectioning of carbon nanotube-to-metal junctions for high spatial resolution chemical and structural analysis

AbstractIn this study, we have demonstrated successful site-specific cross-sectioning of carbon-nanotube - metal junctions which provided samples suitable for high resolution transmission electron microscopy and electron energy loss spectroscopy. For the cross-sectioning, we have suggested a modified technique based on combination of the Focused Ion Beam (FIB) lift-out and the conventional Ar+ ion milling techniques. Electron-transparent cross-sections of multiwall carbon nanotubes showing no significant surface amorphization or Ga contamination (typical artifacts of conventional FIB lift-out technique) were obtained. High-resolution transmission electron microscopy and electron energy loss spectroscopy of a multi-wall carbon nanotube cross-section have been carried out.

Site-specific cross-sectioning of carbon nanotube-to-metal junctions for high spatial resolution chemical and structural analysis

ABSTRACTIn this study, we have demonstrated successful site-specific cross-sectioning of carbon-nanotube - metal junctions which provided samples suitable for high resolution transmission electron microscopy and electron energy loss spectroscopy. For the cross-sectioning, we have suggested a modified technique based on combination of the Focused Ion Beam (FIB) lift-out and the conventional Ar+ ion milling techniques. Electron-transparent cross-sections of multiwall carbon nanotubes showing no significant surface amorphization or Ga contamination (typical artifacts of conventional FIB lift-out technique) were obtained. High-resolution transmission electron microscopy and electron energy loss spectroscopy of a multi-wall carbon nanotube cross-section have been carried out.