Preparation Of Foils Research Articles

Preconcentration of Trace Amounts of Zinc and Copper from Water Samples onto Polystyrene Foils Prior to Determination by Wavelength-Dispersive X-ray Fluorescence Spectrometry

A simple method of determining trace amounts of zinc (Zn) and copper (Cu) by wavelength-dispersive X-ray fluorescence spectrometry (WDXRF) is proposed. The method is based on the preparation of special foils enriched with specified trace elements. In the first step, the elements were preconcentrated by liquid-liquid extraction using dithizone in CCl4. In the second step, the obtained extracts containing determined elements were mixed with a solution of polystyrene in CH2Cl2. After the evaporation of the organic solvents the produced foils were peeled off the Petri dish and analyzed by WDXRF. The method of preconcentration of trace amounts of Zn and Cu as well as the procedure of obtaining suitable foils for XRF measurements were optimized. We studied the effects of parameters such as the amounts of complexing agent and selected interfering elements, pH, and volume of analyte solutions on the recovery of Zn and Cu in the extraction process and their determination. The homogeneity of the mass per unit area of the prepared foils was evaluated using the internal standard method. The proposed method allows determination of trace amounts of Zn and Cu with about 98% recovery and 7 ng mL−1 detection limits for 250 mL of water. The method is useful for routine determination of trace metals in aqueous samples by X-ray fluorescence spectrometry.

Synthesis and characterization of the diamond/copper composites produced by the pulse plasma sintering (PPS) method

The rapidly advancing miniaturization of micro-electronic devices leads to a considerable increase of the amount of heat evolved by electronic circuits. This, combined with the inexorable increase in the clock speed of running such devices, results in skyrocketing power densities in modern devices such as microprocessors and other high-performance chips. It is anticipated that, in the current decade, the power density will reach the limiting value possible to dissipate by the materials used at the present. As predicted by Patrick Gelsinger (Intel CTO), during the next few years the semiconductor industry will be “heating to a meltdown”, with the trend of power densities in modern microprocessors literally escalating toward levels found within a nuclear reactor. In order to enable the packing density of micro-electronic devices to be further increased, we need new materials of higher thermal conductivity. Another requirement is that these materials should have a thermal expansion coefficient comparable with that of the microelectronic substrate material so as to avoid damage to the heat sink/substrate joint due to the thermal stresses induced by cyclic temperature variation. These requirements can be satisfied by the diamond/metal composites with the metal matrix of high thermal conductivity, such as e.g. Cu. The thermal properties (conductivity, thermal expansion) of the composites can easily be tailored by modifying the metal/diamond proportion. However, within the temperature range of consolidation of these composites, diamond is a metastable phase and may, during the consolidation, be transformed into its stable phase i.e. graphite. This can be avoided by conducting the process under conditions of thermodynamic stability of diamond, i.e. by applying appropriately high consolidation pressure (4–5GPa), which however increases the production costs. The authors of the present study experimented with producing copper/diamond composites with 50vol.% of diamond particles under conditions of thermodynamic instability of diamond by consolidating the composite using the pulse plasma sintering (PPS) method. The process temperature was 900°C, the pressure was 80MPa and the sintering time was 10min. The phase composition, density and microstructure of the composites thus obtained were examined. The Cu/diamond PPS-consolidated composites had a theoretical density of 96% and the diamond particles were distributed uniformly within the copper matrix. The major challenge in the development of this kind of composites is to obtain a well bonded interface between the copper and the diamond. To increase the interfacial bonding in the Cu/diamond composites the copper was alloyed with chromium to form Cu0.8Cr. The Cu0.8Cr/diamond composite had a theoretical density of 99.8% and was characterized by a strong bond between the diamond and the copper matrix, which was due to formation the interface between diamond and copper matrix. This paper presents the results of TEM examinations of this interface and describes the method of preparation of thin foils cut through it using a FIB technique.

Localized Grounding, Excavation, and Dissection Using In‐Situ Probe Techniques for Focused Ion Beam and Scanning Electron Microscopy: Experiments With Rock Varnish

While investigating rock varnish, we explored novel uses for an in-situ micromanipulator, including charge collection, sample manipulation, as well as digging and dissection at the micron level. Dual-beam focused ion beam microscopes (DB-FIB or FIBSEM) equipped with micromanipulators have proven to be valuable tools for material science, semiconductor research, and product failure analysis. Researchers in many other disciplines utilize the DB-FIB and micromanipulator for site-specific transmission electron microscope (TEM) foil preparation. We have demonstrated additional applications for in-situ micromanipulators.

Application of transmission electron microscopy and focused ion beam tomography for microstructure characterization of tungsten based materials

Tungsten and its alloys are considered as structural materials for plasma-facing applications. The divertor design requires a material with a low ductile–brittle transition temperature and a recrystallization temperature (TR) of about 1570 K. One of the materials under consideration is W–1.7%TiC. The aim of this work was to perform a detailed microstructural characterization of the two materials, pure W and W–1.7%TiC alloy, by electron microscopy and a new technique, electron tomography. Thin foil preparation for transmission electron microscopy investigation of W-based materials is extremely difficult. After many trials by various techniques, a method for thin foil preparation was successfully elaborated and a transmission electron microscope (TEM) investigation was carried out. A pure tungsten specimen was investigated as a reference material. The application of TEM and focused ion beam–scanning electron microscopy techniques enables the identification of some creep-induced features in pure tungsten and the determination of the size and morphology of three-dimensional pores and particles in W–TiC-based alloy.

Preparation of Ni-Co Alloy Foils by Electrodeposition

Electrodeposition of Ni-Co alloy foils on titanium substrate was performed in an acid chloride- sulphate bath. The influences of electrodeposition parameters such as current density, temperature, pH value, cobalt sulphate and saccharin concentration on composition and current efficiency were investigated in detail. The morphology and the microstructure of deposits were analyzed by SEM and XRD, respectively. The results indicated that the optimum parameters were current density 3-4 A/dm2, pH 2-3, temperature 40-50?C, cobalt sulphate 20 g/l and saccharin 2-3 g/l. Chemical analysis of the deposits by EDS revealed anomalous Ni-Co codeposition occured in this system. The SEM showed that hydroxide particles were not present on the surface and that fine-grain, smooth and compact Ni-Co alloy deposits were obtained. The crystallographic structures of Ni-Co alloy foils were the fcc Ni solid solution. The Ni-Co alloy foils with Co content 17.3-37.2 wt% and thickness of 20-45 μm were bright with low residual stress and super toughness.

Effect of gallium focused ion beam milling on preparation of aluminium thin foils

Focussed ion beam milling has greatly extended the utility of the atom probe and transmission electron microscope because it enables sample preparation with a level of dimensional control never before possible. Using focussed ion beam it is possible to extract the samples from desired and very specific locations. The artefacts associated with this sample preparation method must also be fully understood. In this work, issues specifically relevant to the focussed ion beam milling of aluminium alloys are presented. After using the focussed ion beam as a sample preparation technique it is evident that gallium will concentrate in three areas of the sample: on the surface, on grain boundaries and at interphase boundaries. This work also shows that low-energy Ar ion nanomilling is potentially quite effective for removing gallium implantation layers and gallium from the internal surfaces of aluminium thin foils.

Characterization of Graphite Crystal Structure and Growth Mechanisms Using FIB and 3D Image Analysis

AbstractConsidering the significant influence of the morphology of graphite inclusions on the properties of cast iron it is important to understand the correlation between manufacturing parameters and resulting microstructure. In particular, understanding the effect of alloying elements and inoculants on the formation and growth mechanisms of the graphite particles provides the basis for exact tailoring of the microstructure and thus exact tailoring of effective properties of cast iron. Experimental observations of the three‐dimensional (3D) structure of graphite particles, high resolution chemical analysis of nuclei and other inclusions, as well as quantitative characterization of possible growth mechanisms have confirmed certain existing theoretical models for nodular and flake graphite and provided a comprehensive description of all intermediate morphologies. Precise analysis of the graphite's crystal structure based on target preparation of transmission electron microscope thin foils opens additional possibilities for estimating of the properties of different graphite types.

Two-dimensional metallic tungsten nanowire network fabricated by electron-beam-induceddeposition

One-dimensional tungsten nanowires and two-dimensional tungsten nanowire networkswere fabricated on a tungsten substrate by using electron-beam-induced deposition (EBID)without precursor injection. The as-prepared tungsten nanostructures were studied using acombination of energy-dispersive x-ray spectroscopy and selected area electron diffraction. Itwas revealed that the tungsten nanostructures were composed of pure metallic tungsten. TheWO3 oxide formed in the chemical preparation of tungsten foils was probably the source oftungsten for the fabrication of tungsten nanostructures by EBID.

In situ oxidation of zirconium binary alloys by environmental SEM and analysis by AFM, FIB, and TEM

Binary Zr-alloys containing 1%Fe and 1% Ni (large precipitates) and 1% Cr and 0.6% Nb (small precipitates), as well as a pure Zr sample were exposed in situ at 130 Pa water vapour pressure at 415 °C in an environmental SEM. The surface topography and composition of each sample was characterised before in situ experiments, during and after oxidation. After oxidation the surface was characterised by SEM and EDS, AFM and TEM combined with EDS. Focused ion beam was used to prepare cross sections of the metal–oxide interface and for the preparation of TEM thin foils. The oxidation behaviour of precipitates for these alloying elements can be characterised into two large families, those which show a rapid oxidation and those which induce a delayed oxidation in comparison with the Zr-matrix. At 415 °C after 1 h of oxidation for Zr1%Fe and Zr1%Ni, the formation of protrusions could be detected at the surface, being related to underlying SPP in the oxide. On Zr1%Cr and Zr0.6%Nb unoxidised SPPs were observed in the oxide, close to the metal–oxide interface. These SPPs were, however, oxidised close to the outer surface of the oxide. The surface roughness was increased for all materials after in situ oxidation, however, only for Zr1%Fe and Zr1%Ni protrusions appeared on the surface during oxidation. It was subsequently demonstrated that these latter correspond to the position of SPPs. For Zr1%Fe the surface roughness increased more than in the other materials and on these protrusions small iron oxide crystals have been observed at the surface. These observations confirm that Fe has a different behaviour compared to the other SPP forming elements, and it diffuses out to the free surface of the material. These alloying elements being the constituents of the commercial alloys (Fe and Cr for Zircaloy-4; Fe, Cr and Ni for Zircaloy-2 and Nb for all Nb-containing alloys), this study allows to separate their individual influence and can allow a subsequent comparison to the behaviour of those more complex alloys.

Novel application of focused ion beam electron microscopy (FIB-EM) in preparation and analysis of microfossil ultrastructures: A new view of complexity in early Eukaryotic organisms

Coupled dual-beam focused ion beam electron microscopy (FIB-EM) has gained popularity across multiple disciplines over the past decade. Widely utilized as a stand-alone instrument for micromachining and metal or insulator deposition in numerous industries, the submicron-scale ion milling and cutting capabilities of FIB-EM systems have been well documented in the materials science literature. These capacities make FIB-EM a powerful tool for in situ, site-specific transmission electron microscopy (TEM) ultrathin foil preparation. Recent advancements in the field-emission guns (FEGs) of FIB-EM systems have provided spatial resolution comparable to that of many high-end scanning electron microscopes (SEM), thus providing enhanced imaging capacities with material deposition and material removal capabilities. More recently, FIB-EM preparation techniques have been applied to geological samples to characterize mineral inclusions, grain boundaries, and microfossils. Here, we demonstrate a novel method for analyzing three-dimensional (3D) ultrastructures of microfossils using FIB-EM. Our method, FIB-EM nanotomography, consists of sequential ion milling, or cross sectioning, and concurrent SEM imaging. This technique with coupled dual-beam systems allows for real-time, 3-D ultrastructural analysis and compositional mapping with precise site selectivity and may provide new insights in fossil ultrastructures. Using the FIB-EM nanotomography method, we investigated herkomorphic and acanthomorphic acritarchs (organicwalled microfossils) extracted from the $999 Ma Mesoproterozoic Ruyang Group of North China. The 3-D characteristics of such important but controversial acritarch features as processes and vesicularly enclosed central bodies are described. Through these case studies, we demonstrate that FIB-EM nanotomography is a powerful and useful tool for investigating the three-dimensionality of microfossil ultra- and nanostructures.

TEM foil preparation of sub‐micrometre sized individual grains by focused ion beam technique

Analysis of presolar silicate grains provides new knowledge on interstellar and circumstellar environments and can be used to test models of the Galactic chemical evolution. However, structural information of these grains is rare because sample preparation for transmission electron microscopy is very difficult due to the small dimensions of these grains (<0.5 mum). With the use of the focused ion beam technique thin foils from these grains for transmission electron microscopy analysis can be prepared. Nevertheless, reaching the required precision of some tens of nanometres for the preparation of the transmission electron microscopy foil in the place of interest is not trivial. Furthermore, in the current samples, the grain of interest can only be identified by its different isotopic composition; i.e. there is no contrast difference in scanning electron microscopy or transmission electron microscopy images which allow the identification of the grain. Therefore, the grain has to be marked in some way before preparing the transmission electron microscopy foil. In the present paper, a method for transmission electron microscopy foil preparation of grains about 200 to 400 nm in diameter is presented. The method utilizes marking of the grain by Pt deposition and milling of holes to aid in the exact orientation of the transmission electron microscopy foil with respect to the grain. The proposed method will be explained in detail by using an example grain.

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.

Effect of sample bending on diffracted intensities observed in CBED patterns of plan view strained samples

Convergent beam electron diffraction is used to study the effect of the sample bending on diffracted intensities as observed in transmission electron microscopy (TEM). Studied samples are made of thin strained semiconductor Ga 1− x In x As epitaxial layers grown on a GaAs substrate and observed in plan view. Strong variations of the diffracted intensities are observed depending on the thinning process used for TEM foil preparation. For chemically thinned samples, strong bending of the substrate occurs, inducing modifications of both kinematical and dynamical Bragg lines. For mechanically thinned samples, bending of the substrate is negligible. Kinematical lines are unaffected whereas dynamical lines have slightly asymmetric intensities. We analyse these effects using finite element modelling to calculate the sample strain coupled with dynamical multibeam simulations for calculating the diffracted intensities. Our results correctly reproduce the qualitative features of experimental patterns, clearly demonstrating that inhomogeneous displacement fields along the electron beam within the substrate are responsible for the observed intensity modifications.

Oxidation of Elemental Gold in Alcohol Solutions

Gold is designated as the noblest metal because of its chemical inertness. It is known to dissolve in cyanide solutions in the presence of air or H2O2 or in halogen-containing solutions, aqua regia being the most famous example. Herein, we report a unique thiol, especially 4-pyridinethiol (4-PS), assisted dissolution of Au in alcohol solutions. Although dissolution was found to be very selective for pyridinethiols, such a phenomenon is astonishing since thiols are commonly used as etch resists for Au and even 4-PS is extensively used as a surface modifier for Au. To gain further understanding of the dissolution process, the influence of the reaction conditions was extensively studied. On the basis of the obtained results, a mechanism for the dissolution reaction is proposed. Fascinatingly, by tuning of the reaction conditions, this phenomenon can be applied in selective preparation of self-supporting nanometer-thick Au foils.

Process Technology for High-Resolution AM-PLED Displays on Flexible Metal Foil Substrates

The first successful integration of poly-Si thin-film- transistor (poly-Si TFT) backplane with polymer light-emitting diodes (PLEDs) onto a flexible stainless-steel foil is described, and a high-resolution (230 DPI) monochrome active- matrix polymer light-emitting diode (AM-PLED) display is demonstrated. The process technology required to implement this high-resolution AM-PLED display onto a flexible metal foil substrate is discussed. This technology primarily consists of the preparation of flexible metal foils, fabrication of the poly-Si TFT backplane, and integration with top-emitting PLEDs.

Polyimide foils as backing supports for optical filters

Optical filters for X-ray telescopes require thin, mechanically and thermally stable, self-supporting backings. Polyimide foils, 25 cm in diameter, having such characteristics and with areal density of 25–140 μg/cm 2, have been produced applying a modified method of foil preparation by in situ polymerisation. The modified method and results of mechanical properties tests of the foils are described.

Preparation and investigation of thick carbon foils prepared by laser plasma ablation deposition

Carbon foils prepared by laser plasma ablation deposition using a power density of > 1 GW / cm 2 are so far the only ones which have been shown to have a total random orientation of the nanocrystallites and thus the theoretically best resistance against irradiation damage caused by ion bombardment. Need for longer lifetimes of carbon stripper foils was observed firstly in tandem accelerator experiments with heavy ions. There the required thickness is 3 to 10 μ g / cm 2 and the plant was developed to meet these needs. Thicker carbon stripper foils are required as dead-section strippers and post-strippers. For the stripping of H - beams in the GeV range thick ( > 100 μ g / cm 2 ) carbon stripper foils are required. The new plant which should facilitate the ablation deposition for this type of foils of unlimited thickness has been constructed. First results are presented about the preparation of thick ( > 50 μ g / cm 2 ) carbon stripper foils of this kind and the applicability of the results to the preparation of carbon stripper foils of several hundred μ g / cm 2 is discussed. For the application as gas detector windows very good chemical resistance is required if the carbon foil becomes hot due to the energy loss of the ion beam. Investigations for a 4 μ g / cm 2 laser plasma carbon foil window transmitting 10 p μ A of 3 MeV C 2 + 12 are reported. If very uniform electronic energy loss is required the corrugated structure, caused by the betaine parting agent on laser plasma carbon foils, is not suited. Therefore, it was tried to utilize release agents of different types of evaporated salt layers which were covered by 100 μ g / cm 2 copper in the same vacuum process. The floating success rates for those release agent combinations are reported.

Recent advances in FIB–TEM specimen preparation techniques

Preparing high-quality transmission electron microscopy (TEM) specimens is of paramount importance in TEM studies. The development of the focused ion beam (FIB) microscope has greatly enhanced TEM specimen preparation capabilities. In recent years, various FIB–TEM foil preparation techniques have been developed. However, the currently available techniques fail to produce TEM specimens from fragile and ultra-fine specimens such as fine fibers. In this paper, the conventional FIB–TEM specimen preparation techniques are reviewed, and their advantages and shortcomings are compared. In addition, a new technique suitable to prepare TEM samples from ultra-fine specimens is demonstrated.

The effect of ion-beam specimen preparation techniques on vacancy-type defects in silicon

Ion bombardment is frequently used in the preparation of thin foils of a variety of materials for analysis by transmission electron microscopy (TEM) and related techniques. We have studied in detail the effects of such specimen preparation techniques on nanometre-sized cavities in silicon by comparing ion-beam milled cross-sectional specimens with those prepared using a small-angle cleavage technique. The cavities have been formed by a prior implantation of energetic helium ions and a high-temperature anneal. In the specimens prepared by ion-beam techniques in two different commercial systems, there is a clear effect on the small cavities. Specifically, the cavities are observed to migrate away from the original surface at both room temperature and liquid nitrogen temperature. The effect is discussed in the context of the interaction of the cavities with mobile vacancies and interstitials injected by the ion bombardment. We believe this to be an important effect that must be taken into account when using TEM techniques to study defects in semiconductors.

Focused Ion Beam (FIB): Applications in Micro- and Nanoanalysis in Geosciences and Applied Mineralogy

Abstract Recently the focused ion beam (FIB) tool has been successfully used to prepare site-specific geological specimens for subsequent analysis by TEM, and as a stand-alone instrument for micromachining of materials such as diamond. FIB enables to prepare a TEM foil from the specific location of interest. TEM foils with the dimensions 20 × 10 × 0.150 micrometer can be cut from nearly any sample by means of a Ga-ion beam. The preparation of a TEM-ready foil with similar dimensions takes about 4 hours in a fully automated process, which is significantly faster than conventional argon ion milling. It is this unique possibility of site-specific TEM foil preparation, which enables TEM investigation of submicron-sized mineral inclusions in mantle minerals such as diamond, garnet or olivine, thus providing an insight into the pressure-temperature conditions and chemical composition of the Earth's mantle during formation of the encapsulating minerals. A FEI FIB200 instrument is operated at the GFZ Potsdam since more than two years and TEM foils from many rock-forming minerals such as olivine, garnet, pyroxene, amphibole, quartz, apatite or glass, metals, ceramic materials and even microfossils have been successfully prepared and subsequently investigated by TEM. The first finding of nanometre-sized diamond aggregates in melt inclusions enclosed in a silicate mineral (pyroxene) in mantle xenoliths from Hawaiian lavas illustrates the enormous potential of this technique. Another novel application of FIB in geosciences is micromachining diamonds, which are used for high-pressure diamond anvil cells (DAC).