The crystal structure of the Al2CuMg S-phase precipitate in an Al matrix has been determined by quantitative high resolution electron microscopy. This work combines techniques of image processing and quantitative comparison between experimental and simulated images with automatic refinement of imaging and structural parameters.

We have developed new methods to quantify the data acquired by electron spectroscopic imaging (ESI) in an energy filtering TEM. The analysis is based on recording series of energy filtered images across inner-shell loss edges or in the low-loss region. From the series of ESI images, electron energy loss (EEL) spectra can be extracted and subsequently analysed using standard EELS quantification techniques. From an ESI series one can measure the absolute amount (area density) of an element in the given sample area or the concentration ratios of one element with respect to other elements. Spectrum line-profiling has been shown to be an efficient way to acquire and present the information on the chemistry of an interface. The results obtained for different metallisation layer systems show that segregation in the monolayer range can still be analysed with high spatial resolution. For the study of the energy-loss near-edge structure (ELNES) a higher energy resolution is required. ESI series with narrow energy window width can be used to distinguish between different bonding states of a given element and is demonstrated for thin films of diamond and amorphous carbon.

The structure and chemical composition of two types of precipitates in the system TiB2-WB2-CrB2 were studied by means of high-resolution TEM and energy filtering TEM. Type I particles (W2B5 structure) are precipitated at the basal plane of the hexagonal matrix whereas type II precipitates are thin platelets lying parallel to the {1100} prism planes. Lattice imaging yields displacements of the metal positions with respect to the matrix. Information on the chemical composition at high lateral resolution is obtained from elemental maps of all chemical constituents using electron spectroscopic imaging (ESI). The type II precipitates show a decrease in the B and Ti concentration, whereas the tungsten concentration increases and the Cr is homogeneously distributed. The HRTEM results combined with the results of the elemental maps allow to develop a structural model based on the intergrowth of the β-WB structure in the TiB2-rich matrix. The two deficient boron layers in W0.5Ti0.5B with a spacing of 0.38 nm can be used to examine the resolution limit of ESI.

The spatial redistribution of alloying elements and impurities near grain boundaries in several stainless steel alloys arising from non-equilibrium processes have been measured by analytical electron microscopy (AEM) in a field emission scanning transmission electron microscope. Radiation-induced segregation (RIS) has been shown to result in significant compositional changes at point defects sinks, such as grain boundaries. The influence of irradiation dose and temperature, alloy composition, prior heat treatment, and post-irradiation annealing on the grain boundary composition profiles have been investigated. Understanding the importance of these microchemical changes relative to the radiation-induced microstructural change in irradiation-assisted stress corrosion cracking (IASCC) of the irradiated materials is the primary goal of this study.

The Σ5 (31O)/[001] symmetric tilt grain boundary (STGB) in the face centered cubic (FCC) metal aluminum with 1at% copper has been studied. The model grain boundary has been fabricated by ultra-high vacuum diffusion bonding of alloy single crystals. The segregation of the copper has been encouraged by annealing the sample after bonding at 200 °C. TEM samples of this FCCmaterial were prepared with a new low voltage ion mill under very low angles.

The atomic structure of the Σ5(310)/[001] STGB for this system was modeled with electronic structure calculations. These theoretical calculations of the interface structure indicate that the Cu atoms segregate to distinct sites at the interface. High resolution electron microscopy (HRTEM) and analytical electron microscopy including electron energy spectroscopic imaging and X-ray energy dispersive spectrometry have been used to explore the segregation to the grain boundary. The HRTEM images and the analytical measurements were performed using different kinds of microscopes, including a Philips CM300 FEG equipped with an imaging energy filter. The amount of the segregated species at the interface was quantified in a preliminary way. To determine the atomic positions of the segregated atoms at the interface, HRTEM coupled with image simulation and a first attempt of a holographic reconstruction from a through-focal series have been used.

Cu bicrystals were doped with different amounts of Bi and annealed at various temperatures. The segregation at the grain boundary (GB) was analyzed by energy dispersive X-ray analysis (EDX) in the scanning transmission electron microscope (STEM). It is found that with both increasing temperature and increasing Bi content the amount of faceting of the GB increases, finally reaching complete faceting. This final state is distinguished by brittle behavior. By analyzing the shape of pores at the GB we found that the Cu surface energy anisotropy is probably increased by Bi surface segregation.

A complete understanding of the complexities behind the structure-property relationships at materials interfaces requires the structure, composition and bonding to be characterized on the fundamental atomic scale. This level of characterization is beyond the scope of a single imaging or microanalysis technique and so to solve practical interface problems, correlation between multiple techniques must be achieved. Here we describe recent advances in the JEOL 2010F 200kV field-emission STEM/TEM that now allow atomic resolution imaging and analysis to be obtained in both TEM and STEM mode and discuss two applications of these techniques

The core structures of two symmetric tilt [001” grain boundaries in yttria- stabilized cubic zirconia are determined by Z-contrast imaging microscopy. In particular, near-σ=13 (510) and σ=5 (310) boundaries are studied. Both grain boundaries are found to be composed of periodic arrays of basic grain-boundary structural units, whose atomic structures are determined from the Z-contrast images. While both grain boundaries maintain mirror symmetry across the boundary plane, the 36° boundary is found to have a more compact structural unit than the 24° boundary. Partially filled cation columns in the 24° boundary are believed to prevent cation crowding in the boundary core. The derived grain boundary structural models are the first developed for ionic crystals having the fluorite structure

Energy dispersive x-ray (EDX) spectrum imaging has been performed in a scanning electron microscope (SEM) on a metal/ceramic braze to characterize the elemental distribution near the interface. Statistical methods were utilized to extract the relevant information (i.e., chemical phases and their distributions) from the spectrum image data set in a robust and unbiased way. The raw spectrum image was over 15 Mbytes (7500 spectra) while the statistical analysis resulted in five spectra and five images which describe the phases resolved above the noise level and their distribution in the microstructure

Epitaxial thin films of rare-earth hexaaluminates on basal plane sapphire have been produced by chemical solution deposition. LaAl11O18 films with magnetoplumbite structure grow with (0001)HA||(0001)S and [1100]HA||[2110]s orientation relationship

To investigate the stucture of the interface exit wave reconstruction of focus series was carried out using a field emission TEM. Due to the inversion of the imaging process major artefacts at the interface can be eliminated. Exit waves were simulated based on different interface models and were compared with the reconstructed waves to localize the positions of the atoms at the interface. Two different types of interfaces were observed in the samples. One of the types, in which the spinel block of hexaaluminate faces the sapphire with the mixed cation layer with occupied octahedra and tetrahedra, is characterized in detail. Face-sharing of coordination polyhedra is avoided to large extent

The atomic structures of σ=3, 9 and 27 boundaries, and multiple junctions in β-SiC were studied by high-resolution electron microscopy (HREM). Especially, the existence of the variety of structures of σ=3 incoherent twin boundaries and σ=27 boundary was shown by HREM. The structures of σ=3, 9 and 27 boundary were explained by structural unit models. Electron energy-loss spectroscopy (EELS) was used to investigate the electronic structure of grain boundaries. The spectra recorded from bulk, {111}σ=3 coherent twin boundary (CTB) and {1211}σ=3 incoherent twin boundary (ITB) did not show significant differences. Especially, the energy-loss corresponding to carbon 1s-to Φ* transition was not found. It indicates that C atoms exist at grain boundary on the similar condition of bulk

The dominant factor in determining the atomic structure of grain boundaries is the crystal structure of the material, e.g. FCC vs. BCC. However, for a given crystal structure, the structure of grain boundaries can be influenced by electronic effects unique to the element comprising the crystal. Understanding and modeling the influence of electronic structure on defect structures is a key ingredient for successful atomistic simulations of materials with more complicated crystal structures than FCC. We have found that grain boundary structure is a critical test for interatomic potentials. To that end, we have fabricated the nominally identical Σ5 (310)/[001] symmetric tilt grain boundary in three different BCC metals (Nb, Mo, and Ta) by diffusion bonding precisely oriented single crystals. The structure of these boundaries have been determined by high resolution transmission electron microscopy. The boundaries have been found to have different atomic structures. The structures of these boundaries have been modeled with atomistic simulations using inter-atomic potentials incorporating angularly dependent d–state interactions, as obtained from Model Generalized Pseudopotential Theory. We report here new experimental and theoretical results for Ta

A [100] 45° twist plus 7.5° tilt grain boundary in aluminium prepared by cold rolling and annealing has been studied by high-resolution electron microscopy. The direct interpretability of the image features in terms of atomic column positions allows structural models of the grain boundary to be developed. The boundary exibits a high concentration of steps due to the 7.5° tilt from a perfect [100] 45° quasiperiodic misorientation. Occurrence of co-incidence and pseudo co-incidence of atomic planes across the interface appears to play an important role in the formation of steps along this boundary. Local relaxation of atoms resulting from the perturbation of the [100] 45° twist bi-crystal determines the boundary structure

A very thin bicrystal film, prepared by depositing gold onto a {111} germanium substrate, then annealing and removing it, has been studied by HREM. The crystals grow predominantly in the orientations {111} and (111) which are related by a 60° rotation (Σ3 CSL) and bounded by {121} facets. In contrast to the boundaries studied in thicker films, these {112} facets extend through the depth of the film. Another crystal within the film also had a {111} orientation, but rotated by around 20° from the other crystals. A short length of boundary was found that was edge-on, symmetrical, facetted on (213) planes, and corresponding to Σ;7 (or Σ;21). A copper 1111 film did not show edge-on boundaries

The rigid body translation across the facets were measured and found to vary depending on the proximity to facet junctions. An expansion at the boundary was the general case

Titanium/titanium nitride anti-reflective coatings (ARC) are widely used in the semiconductor industry during photolithography of aluminum metal interconnect lines. The quality and effectiveness of these coatings, however, depend strongly on the ability to control reaction products formed at film interfaces during processing. In the present study, formation of an Al-N compound at the interface between Ti/TiN ARC/BARC and Al-(0.5 wt. %)Cu interconnect was investigated. The effects of deposition temperatures for individual films and ensuing thermal cycling of the whole metal stack on formation of intermetallics were evaluated. The composition and chemical bonding state of an aluminum nitride interfacial layer was evaluated by x-ray photoelectron spectroscopy (XPS) of blanket wafers. These results were combined with measurements made by energy filtered transmission electron microscopy (EFTEM) of thickness and continuity of the film in specimens prepared by focused ion beam milling (FIB). Formation of AIN depends on the thermal cycling history of the metal stacks

The Al-0.5wt%Cu alloys in Ti-TiN/Al/Ti-TiN metal interconnects were investigated using blanket and patterned films deposited on SiO2. Distribution of Cu and Ti within the Al films was determined using Resistivity (Rs), X-ray Diffraction (XRD), Rutherford Backscatter Spectroscopy (RBS), and Secondary Ion Mass Spectroscopy (SIMS). The location of Cu, Ti, Al and their intermetallics were studied in a CM300 field emission gun (FEG) TEM using Energy Filtered Transmission Electron Microscopy (EFTEM) with a Gatan Imaging Filter (GIF). No significant differences were observed with Rs or XRD textural analysis. Elemental distribution analysis from RBS and SIMS revealed relatively higher concentrations Cu at the Al/Ti-TiN barrier interface. This was attributed to sputtering bias during the start of the Al deposition and the subsequent snow plowing of Cu during the growth of the TiAl3 intermetallic. TEM imaging and elemental analysis showed that Cu is completely dissolved into solution at deposition temperatures ≥ 300°C. At temperatures ≤ 250°C some (Al2Cu) precipitates were observed on grain boundaries. Continued thermal cycling does not effectively change the elemental distribution. Therefore, it can be concluded that the solid solubility of 0.5wt%Cu in Al was not reached at these low temperatures or during the subsequent thermal cycling

The interfacial interaction between Cr thin films and multi-component oxide glasses has been observed by means of high spatial resolution electron energy loss spectroscopy. Besides a partially oxidized Cr thin layer, a ∼5nm wide Cr diffusion layer is seen. Chromium oxidation at the interface results from the difference between the heats of oxide formation. Ion exchange between Cr2+ and alkaline earth ions then causes the formation of the diffusion layer. The electronic states of the Cr in this diffusion layer are different from that in the oxidized layer. Strong interaction between Cr and O in the diffusion layer suggests that such a layer could be responsible for the formation of a strong Cr/glass interface

Analytical electron microscopy at high spatial resolution in a scanning-transmission mode has been used to investigate the effects of glassy or crystalline material additions on grain boundary chemistry in yttria-stabilized zirconia polycrystals. Powders of additive phase were mixed into 3-mol% yttria-stabilized tetragonal zirconia polycrystals (‘3Y-TZP’) or 8-mol% yttria-stabilized cubic zirconia polycrystals (‘8Y-CSZ’). Zirconias processed without additive phases were also examined

Without additives, grain boundaries were depleted in zirconium and enriched in yttrium. In 3Y-TZP with I wt% borosilicate glass, silicon was observed only at triple points, but not in grain boundaries. In 3Y-TZP with 1 wt% barium silicate glass, barium was observed both along grain boundaries and at triple points, whereas silicon was detected only within the triple points. This suggests either the composition of the additive phase at the grain boundary is different from that at the triple points, or that barium ions segregate to grain boundaries during processing. In 8Y-CSZ with I wt% silica, silicon was observed in grain boundaries by an EDS spatial differencing technique. In 8Y-CSZ with 10 wt% alumina, EDS revealed aluminum at all grain boundaries examined

Effect of moisture on the oxidation of copper was studied using in situ UHV-TEM. The ultra high vacuum condition is required for minimum contamination effects. The initial observations show that the water vapor reduces the oxide as well as reduces the rate of oxidation if both oxygen gas and water vapor are simultaneously used. Based on these observations, we have speculated on the role of moisture in the solid state reactions involved in copper oxidation

Ion-implanted diamond-like carbon (DLC) films have been characterized by techniques based on electron energy-loss spectrometry using an imaging energy filter on a 300kV TEM. Nitrogen implantation results in increased sp2 bonding and a 1.3 eV shift to higher binding energies for carbon-K. Argon implantation results in a smaller increase in sp2bonding with no detectable binding energy shift. The fraction of implanted species retained is much smaller for Ar than for N. Differences in behavior between N- and Ar-implanted DLC are consistent with expected chemical reactions. Preliminary results demonstrate the feasibility of mapping the Φ*/σ* intensity (sp2/sp3) ratio by energy-filtered TEM as an alternative to spectrum imaging in STEM mode