Ion Beam Lift-out Technique Research Articles

Size-dependent amorphization of cementite lamellae in a tribolayer

The deformation and structural evolution characteristics of cementite in tribolayers significantly impact the friction and wear properties of pearlitic steels. However, the mechanism and size dependency of cementite amorphization remain unclear. Herein, the focused ion beam (FIB) lift-out technique was used to prepare transmission electron microscopy (TEM) samples of tribolayers formed during dry sliding of pearlitic steel. The microstructure of and elemental distributions in the tribolayers were characterized. Furthermore, molecular dynamics (MD) simulations were employed to analyze the behavior of dislocation slip systems in ferrite that extended toward cementite and induced amorphization. The results indicated that cementite amorphization occurred prior to dissolution within the tribolayer. Dislocation slips at the phase interface resulted in C diffusion and cementite amorphization. The transformation of cementite was size dependent. Thin lamellae transformed into amorphous lamellae, while local deformation and shear bands formed in thick lamellae. These research findings could contribute to rational design of cementite and to control of its structural evolution behavior within a tribolayer, thereby enhancing the wear resistance of a material.

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.

Characteristics of hydrogen embrittlement in high-pH stress corrosion cracking of X100 pipeline steel in carbonate/ bicarbonate solution

Stress corrosion cracking (SCC) of X100 grade pipeline steel was researched in carbonate/bicarbonate solutions by using slow strain rate tensile (SSRT) tests, electrochemical testing, X-ray photoelectron spectroscopy (XPS), electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), the focused ion beam (FIB) lift-out technique and transmission electron microscopy (TEM). It is found that the X100 pipeline steel has low SCC sensitivity at the open circuit potential (OCP) and has high susceptible to SCC owing to the combined effect of anodic dissolution (AD) and hydrogen embrittlement (HE) at the applied cathodic potentials in carbonate/ bicarbonate solutions. At applied cathodic potentials less than about −950 mV, the SCC processes of X100 steel are dependent on AD and HE, while at more negative applied potentials, HE plays a more dominant role. The detailed SCC mechanism was studied by advanced detection methods. The results show that cracks propagated along the interface with low residual strain at various cathodic potentials, indicating that the low residual path is more active for both the anodic reaction and dislocation emission, and the high residual strain area may act as the cathodic zone. This phenomenon will be helpful to the design of high-SCC-resistant high-strength pipeline steel.

Irradiated microstructure of U-10Mo monolithic fuel plate at very high fission density

Monolithic U-10Mo alloy fuel plates with Al-6061 cladding are being developed for use in research and test reactors as low enrichment fuel (<20% U-235 enrichment) as a result of its high uranium loading capacity compared to that of U-7Mo dispersion fuel. These fuel plates contain a Zr diffusion barrier between the U-10Mo fuel and Al-6061 cladding that suppresses the interaction between the U-Mo fuel foil and Al alloy cladding that is known to be problematic under irradiation. Different methods have been employed to fabricate monolithic fuel plates, including hot-rolling with no cold-rolling. L1P09T is a hot-rolled fuel plate irradiated to high fission density in the RERTR-9B experiment. This paper discusses the TEM characterization results for this U-10Mo/Zr/Al6061 monolithic fuel plate (∼59% U-235 enrichment) irradiated in Advanced Test Reactor at Idaho National Laboratory with an unprecedented high local fission density of 9.8E+21 fissions/cm3. The calculated fuel foil centerline temperature at the beginning of life and the end of life is 141 and 194 °C, respectively. TEM lamellas were prepared using focus ion beam lift-out technique. The estimated U-Mo fuel swelling, based on the fuel foil thickness change from SEM, is approximately 76%. Large bubbles (>1 μm) are distributed evenly in U-Mo and interlink of these bubbles is evident. The average size of subdivided grains at this fission density appears similar to that at 5.2E+21 fissions/cm3. The measured average Mo and Zr content in the fuel matrix is ∼30 at% and ∼7 at%, respectively, in general agreement with the calculated Mo and Zr from fission density.

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.

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.

Specimen preparation for three-dimensional atom probe using the focused ion-beam lift-out technique

T.Yamamoto,, Y. Hanaoka, N. Mayama, T. Kaito, T. Adachi, M. Nojima 3 and M. Owari 1,4 1 Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan 2 SII Nanotechnology Inc., 36-1 Takenoshita, Oyama-cho, Sunto-gun, Shizuoka 410-1393, Japan 3 Research Institute of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan 4 Environmental Science Center, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan y1ndggi7@iis.u-tokyo.ac.jp

Epitaxial Directional Growth of Tin Oxide (101) Nanowires on Titania (101) Substrate

Highly aligned single crystal SnO2 (101) nanowires were epitaxially grown on TiO2 (101) substrates by thermal evaporation via Au-catalyzed vapor−liquid−solid (VLS) growth. The orientation relationship and interface structure between the nanowires and the substrate were determined by X-ray pole figure and high resolution transmission electron microscopy (HR-TEM) combined with the focused ion beam (FIB) lift-out technique. Epitaxially grown SnO2 (101) nanowires exhibited three angular growth directions ([101], [011], and [011]) with different inclination angles to the substrate due to a tetragonal crystal structure. An atomic stacking model was proposed to describe the angular growth of SnO2 (101) nanowires with ⟨101⟩ growth directions. The obtained results are expected to provide an understanding of the growth direction of nanowires and heteroepitaxial relationships between nanowires and substrate to synthesize the well-aligned SnO2 nanowires, which can be integrated into the electronic devices and lead t...

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/TEM Characterization of the Composition and Structure of Core/Shell Cu−Ni Nanowires

Characterization of composition and structure is crucial to understanding the properties and performance of nanomaterials. For nanowires and nanotubes, determining radial compositional and structural modulations is particularly challenging. Here we use a focused ion beam (FIB) lift-out technique to show that Cu-Ni core/shell nanowires fabricated by template synthesis are characterized by large, high purity (>99 atom %) copper grains surrounded by much smaller, high purity (>99 atom %) nickel grains.

Analytical transmission electron microscopy study of a natural MORB sample assemblage transformed at high pressure and high temperature

Natural mid-ocean ridge basalt (MORB) samples recovered from diamond-anvil cell (DAC) experiments performed between 33 to 89 GPa and 1700 to 2600 K were studied with a transmission electron microscope (TEM). We used the focused ion beam (FIB) lift-out technique to prepare the recovered high-pressure, laser-heated samples for TEM study. Observations of TEM sections show the presence of five phases for samples transformed at pressures ranging from 33 to 45 GPa: Al-bearing Mg-perovskite, Ca-silicate perovskite, stishovite, and two Al-rich phases. The Al-rich phases were identified by selected area electron diffraction (SAED) patterns and chemical composition analysis, and include the new aluminous (NAL) phase with hexagonal structure and the calcium ferrite (CF) type phase. Chemical analyses obtained by analytical transmission electron microscopy (ATEM) show that Mg-silicate perovskite is the major host for Al, with significant amounts also distributed between the CF-type and NAL phases, and less than 1 wt% in stishovite. Beyond pressures of ~40 GPa (~1100 km depth), the Al content of Mg-perovskite and CF-type phase increases. Between 45 and 50 GPa, the NAL phase disappears. This mineralogical change may explain reported seismic anomalies in subduction zones at mid-mantle depths.

Transmission electron microscopy and atom probe specimen preparation from mechanically alloyed powder using the focused ion-beam lift-out technique

The preparation of transmission electron microscopy (TEM) and atom probe-field ion microscopy (AP-FIM) specimens from mechanically alloyed Ti-Cu-Ni-Sn powder has been explored. Applying the focused ion beam (FIB) based in situ lift-out technique, it has been demonstrated that specimen preparation can be carried on single micrometre-sized powder particles without the use of any embedding media. Since the particles did not incorporate any micropores, as revealed by cross-sectioning, the standard procedure known for bulk samples could be simply implemented to the powder material. A sequence of rectangular cuts and annular milling was found to be a highly efficient way of forming a tip-shaped AP-FIM specimen from a square cross-section blank. A Ga level < or =1 at.% was detected if a low beam current of 10 pA was chosen for the final ion-milling stages. Implanted Ga ions were mostly confined to a zone of about 2 nm in thickness and indicated that ion-induced structural transformations were negligible.

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.

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

AbstractMicrometer 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 ∼10–20 μm × 5 μm × ∼0.1 μm 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.