TEM Specimens Research Articles

The fourth SINQ Target Irradiation Program, STIP-IV

The 4th SINQ Target Irradiation Program (STIP-IV) was performed in 2004 and 2005. More than 1000 specimens from about 40 kinds of materials were irradiated up to 27dpa and 2300appm He in the temperature range of 80–550°C. The majority of specimens were irradiated in helium gas environment. Some specimens were irradiated in contact with lead and lead–bismuth eutectic. Neutron radiography inspections on specimen and target rods were performed before and after irradiation, which revealed some interesting features of the target rods with thermal couples. Neutronic calculations were performed using the proton distribution profile obtained by γ-mapping on the beam window of the AlMg3 target container after irradiation. Irradiation parameters of the specimens such as proton and neutron spectra and fluxes, heat deposition, irradiation dose in terms of displacement damage (dpa), helium and hydrogen concentrations were calculated. Most of the specimens were retrieved. But, more than 360 tensile and TEM specimens were lost due to a leak in a specimen rod occurred during irradiation.

Synthesis and Characterization of SiO<sub>2</sub>/ZnO Core-Shell Spheres

This Study applies to Stöber method for synthesis an characterization of even-sized SiO2micrometer sphere; and then applies to sol-gel method for encapsulation for one layer of ZnO at SiO2spherical surface after regarded it as core so that synthesis SiO2/ZnO core-shell spheres successfully. And observe morphology by FE-SEM and crossection by TEM. The TEM specimen were cut by two-beam FIB. Besides, EDS, XRD and UV-Visible spectroscopy were using for the analysis of composition, crystallization structure, and absorption spectrum, respectively. Experimental results showed that, SiO2spherical surface became smooth after deposition for zinc oxide. The specimen made by FIB more obviously was observed for core-shell distribution by TEM. EDS analysis made us clearly see shell signal with ZnO content, but core signal only is SiO2content. XRD analysis indicated its core-shell sphere signal possessing ZnO content, but UV-Visible absorption spectrometer displayed ZnO has been absorbed in range of UV light, in contrast, it is not absorbed in range of visible light.

Focus Ion Beam for Cross-Sectional TEM Specimen Preparation of Nanomaterials

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Large Thin Area Preparation of Cross-Sectional TEM Specimens of III-V Semiconductors

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

TEM Specimen Preparation with Plasma FIB Xe+ Ions

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Oxidation induced void formation in TEM specimens of Al–Cu–Li alloy

A TEM study has revealed, for the first time, the presence of small (∼3 nm in diameter) voids attached to T1 (Al2CuLi) precipitates present in an artificially aged Al–Cu–Li alloy (Al–2·90Cu–1·63Li–0·29Mg–0·28Ag–0·13Zr). These voids do not form from quenched in excess vacancies but are nucleated at the T1 phase/alloy interface from excess vacancies generated during oxidation of the TEM sample. It is concluded that these voids result from the Kirkendall effect with rapid oxidation of the TEM metal surface occurring by molecular oxygen migration through a highly defective surface oxide layer.

A fast algorithm for computing and correcting the CTF for tilted, thick specimens in TEM

Today, the resolution in phase-contrast cryo-electron tomography is for a significant part limited by the contrast transfer function (CTF) of the microscope. The CTF is a function of defocus and thus varies spatially as a result of the tilting of the specimen and the finite specimen thickness. Models that include spatial dependencies have not been adopted in daily practice because of their high computational complexity. Here we present an algorithm which reduces the processing time for computing the 'tilted' CTF by more than a factor 100. Our implementation of the full 3D CTF has a processing time on the order of a Radon transform of a full tilt-series. We derive and validate an expression for the damping envelope function describing the loss of resolution due to specimen thickness. Using simulations we quantify the effects of specimen thickness on the accuracy of various forward models. We study the influence of spatially varying CTF correction and subsequent tomographic reconstruction by simulation and present a new approach for space-variant phase-flipping. We show that our CTF correction strategies are successful in increasing the resolution after tomographic reconstruction.

Structural characterization of through silicon vias

Different milling strategies for the structural characterization of through silicon vias on silicon wafers and in stacked dies are examined. For investigation of the filling quality, the most appropriate analysis technique is dual beam focused ion beam and scanning electron microscopy. The characterization of thin barriers and Cu seed layers requires transmission electron microscopy. An optimized TEM specimen preparation method is discussed.

Transmission electron microscopy observations on the phase composition and microstructure of the oxidation scale grown on as-polished and yttrium-implanted β-NiAl

Phase transformations and microstructural evolution of thermally grown oxide scale on polycrystalline β-NiAl at 1100 °C up to 6 h, with and without (e.g., as-polished) yttrium implantation, were examined by glancing angle X-ray diffraction, photostimulated luminescence, scanning and transmission electron microscopy. Site-specific TEM specimens were prepared by using focused ion beam in-situ lift-out technique. The oxide scale developed on as-polished β-NiAl consisted of the islands of 390 nm-thick flat regions (e.g., patches) in 916 nm-thick scales. Regardless of microstructure, the oxide scale consisted of α-Al 2O 3 with very little trace of θ-Al 2O 3, and had uniform compressive residual stress. The oxide scale on Y-implanted β-NiAl had a two-layer microstructure: the outer layer was mainly α-Al 2O 3 and the inner layer was made up of α-, δ-, and θ-Al 2O 3 phases. Clearly, the Y addition retarded the θ-to- α Al 2O 3 phase transformation. The oxide scale on Y-implanted β-NiAl, in general, consisted of a 722 nm-thick layer with islands of 470 nm-thick patched regions, some of which contained Y-rich nodules that protruded with thickness up to 1200 nm. Except for islands of patch-regions, the oxide scale developed on Y-implanted β-NiAl was thinner (722 nm) than that on as-polished β-NiAl (916 nm).

Determination of the solubility range and crystal structure of the Mg-rich ternary compound in the Ca–Mg–Zn system

The homogeneity range and crystal structure of the Mg-rich ternary solid solution has been determined using SEM, EPMA/WDS, TEM and X-ray diffraction. This compound has the Ca 3Mg xZn 15−x (4.6 ≤ x ≤ 12) formula at 335 °C. The refinement of the XRD patterns was carried out by Rietveld analysis, XRD data has shown that this solid solution crystallizes in hexagonal structure having P63/mmc (194) space group and Sc 3Ni 11Si 4 prototype. The lattice parameters decrease linearly with decreasing Mg content obeying Vegard’s law. The fractional atomic occupancy of 6h, 4f, 2b and 12k sites of this compound are function of Mg concentration. Focused Ion Beam has been used to lift TEM specimen of the ternary compound and the hexagonal structure has been confirmed by means of selected area electron diffraction data. Based on the atomic occupancy results and the crystallographic details, a three sublattice (Ca)(Zn)(Mg, Zn) 4 model is proposed for this compound.

Subsurface sliding wear damage characterization in Al–Si alloys using focused ion beam and cross-sectional TEM techniques

Abstract This paper illustrates the distinctive capabilities of using focused ion beam (FIB) techniques to elucidate the microstructure that forms beneath the worn regions of samples subjected to laboratory tests under ultra-mild wear (UMW) conditions and those extracted from specific regions of a worn surface of engine blocks. TEM investigations of cross-sectional samples excised with a focused gallium-ion beam to obtain electron transparency of the first few micrometers of the contact surface were effective in providing novel information on the micromechanisms of UMW that are not readily obtained with conventional microscopy. Two FIB sample preparation techniques, namely the lift-out and H-bar techniques were used to prepare site-specific cross-sectional TEM specimens from Al–11% Si alloys subjected to pin-on-disk and dynamometer tests. In both cases, the aluminum matrix was heavily deformed in the top few micrometers below the contact surface, which resulted in the formation of ultrafine grains. Damage to the silicon particles was also observed. Additionally, a tribolayer (or an oil-residue layer) whose thickness increased with sliding cycles, was developed on the contact surfaces. It was concluded that the development of the oil residue layer supported by a layer of ultrafine grain structure was necessary to maintain the low wear rates.

Nanoscale sculpting of ferromagnetic structures by electron beam ablation

We report an electron beam (e-beam) fabrication method to produce sub-5 nm structures, e.g. nanohole-arrays, nanojunctions and nanotips inside a TEM. The method is demonstrated using ferromagnetic nickel cross-sectional TEM specimens as well as electrochemically etched nickel tips. Different e-beam shapes and electron guns are compared, including point versus line focus and field-emission versus LaB6 guns. As an extension of this 2-D patterning of nanostructures, a 3-D nanofabrication technique has been introduced using a high tilt tomographic holder. An electrochemically etched nickel tip of initially 18 nm in radius is sculpted down to sub-5 nm diameter. In some cases, mostly in 3-D nanofabrication, a protrusion during hole drilling was observed and confirmed by EELS as pure nickel.

Twice Flipped - Avoiding Milling Curtains in FIB Prepared TEM Specimens of Nano-Electronics Devices

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

Nanostructured reactive metallic multilayers

Metallic multilayers have been used in cross-sectional TEM specimen geometry to explore nanostructuring routes using ion and electron beams (top-down) as well as self-organised nanopatterning (bottom-up). Intermetallic alloy formation during heat treatment is studied for binary and ternary layer compositions. A choice of pillars (0D), 1D and 2D layer geometries are used to explore dimensionality effects.

TEM analysis of (Ni,Fe)Si2 precipitates in Si

AbstractThe present article provides evidence that Fe impurity atoms in silicon can be gathered by NiSi2 precipitates at temperatures near RT via solid‐state diffusion. Mixtures of silicon and silicide grains, resulting from annealing at 800–900 °C, were analysed. High supersaturation (about 1019–1020 atoms/cm3) of metal impurities in Si was achieved locally by incorporation of nickel and iron atoms from silicide grains into silicon grains during ion milling for TEM specimen preparation. Consequently, particles with local densities of 1013–1014 precipitates/cm3 and average volumes of 10−18–10−16 cm3 formed via diffusion and precipitation. Precipitates with an irregular octahedra shape and platelet‐like habit were found at dislocations. Less frequently, precipitates with a regular octahedra shape were observed in undisturbed matrix. HRTEM images and SAD patterns demonstrate that all precipitates have NiSi2 structure. Ni contents were detected for all precipitates by EDX analysis, but accumulated amounts of Fe could only be proven for some precipitates at dislocations. Quantitative EDX‐analysis revealed Fe/(Fe + Ni) ratios between 16 and 30 at% for these ternary precipitates.

Contamination-Free TEM for High-Resolution Imaging of Soft Materials

Element-selective imaging and analysis at atomic resolution have become possible by the recent advancements in TEM and STEM. However, the spatial resolution in images of soft materials can be limited by electron beam damage and/or contamination. This contamination is a carbonaceous layer deposited on the specimen surface as a result of electron bombardment. Beam-induced specimen contamination is caused by polymerization of hydrocarbons that are present in a TEM specimen chamber. The electron beam reacts with stray hydrocarbons in the beam's path to create hydrocarbon ions, which then condense and form carbon-rich polymerized film on the area being irradiated. Figure 1a shows contamination spots created on a carbon thin foil by illuminating a beam with an intensity of 5.6 × 104 el/nm·s at an accelerating voltage of 200 kV. The thickness of the contamination spots can be estimated by electron energy-loss spectroscopy (EELS). With increase in the irradiation period, the intensity of the zero-loss peak decreases, but the overall intensities in the energy-loss regions of the spectrum increase (Figure 1b). The thickness (D) can be estimated using the equation, D = Λ·ln(It/I0), where Λ is the total mean free path for inelastic scattering, and It and I0 are the integral intensities of the overall spectrum and the zero-loss peak, respectively. Using this equation, the thickness of the contamination was found to be about 600 nm with a 10-minute irradiation.

Off-axis electron holography of Si semiconductors prepared using FIB milling

Off-axis electron holography is a powerful technique that can be used to provide 2D dopant maps of semiconductor materials. Focused ion beam milling is the only technique that can be used to prepare the parallel-sided specimens with the required site specificity for dopant profiling of state-of-the-art semiconductor devices. However, focused ion beam milling introduces artefacts into the thin TEM specimens, such as a surface amorphous layer, Ga implantation and the creation of defects. Here the effects of these artefacts in the semiconductor specimens are examined leading to a better understanding of the reconstructed phase images.

Characterization of a FinFET 6T-SRAM cell by tomography

A 0.186μm2 6T-SRAM cell composed of FinFETs is analysed by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) tomography. It allows to reveal features that are not observed in the conventional (S)TEM images due to the overlap of different materials over the thickness of the TEM specimen. The influence of the specimen thickness on the quality of the obtained tomograms is studied.

TEM specimen preparation by Au +, Ga +, Si + and Si ++ focused ion beams for off-axis electron holography

Silicon specimens containing p–n junctions have been prepared by focused ion beam milling using gallium, single or double charged silicon, and gold focused ion beams. These specimens have been examined before and after annealing for Si prepared samples using off-axis electron holography. The total thickness of the electrically ‘inactive’ layer and of the amorphous region have been measured for the Au, Ga, Si + and Si ++ ions, respectively. We also show that the thickness of this damaged layer can be predicted using collision simulations.

Protective Carbon Deposition for Superior FIB Prepared (S)TEM Specimens

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009