In the course of a thorough investigation of the performance-structure-chemistry interdependency at silicon grain boundaries, we successfully developed a method to systematically correlate aberration-corrected scanning transmission electron microscopy and atom probe tomography. The correlative approach is conducted on individual APT and TEM specimens, with the option to perform both investigations on the same specimen in the future. In the present case of a Σ9 grain boundary, joint mapping of the atomistic details of the grain boundary topology, in conjunction with chemical decoration, enables a deeper understanding of the segregation of impurities observed at such grain boundaries.

The recently discovered compound BeP2N4 that crystallizes in the phenakite-type structure has potential application as a high strength optoelectronic material. Therefore, it is important to analyze experimentally the electronic structure, which was done in the present work by monochromated electron energy-loss spectroscopy. The detection of Be is challenging due to its low atomic number and easy removal under electron bombardment. We were able to determine the bonding behavior and coordination of the individual atomic species including Be. This is evident from a good agreement between experimental electron energy-loss near-edge structures of the Be-K-, P-L2,3-, and N-K-edges and density functional theory calculations.

In this study a two-step heat treatment was applied to high Nb containing γ-TiAl based alloys in order to investigate the initial stage of the lamellae formation in ordered α2-grains as well as in massively transformed γm-grains. The first heat treatment step, conducted in the single α-phase field followed by oil quenching, leads to a microstructure consisting of supersaturated α2-grains and a small volume fraction of γm-grains. The second step of the heat treatment was performed below the eutectoid temperature, i.e. within the (α2+γ)-phase field region and was again followed by oil quenching. There, the formation of ultra-fine γ-lamellae takes place in the α2-grains and (some) fine α2-lamellae are formed in the γm-grains. In both cases the lamellae show a Blackburn orientation relationship with the matrix grain. It was found that the precipitation of γ-laths in the supersaturated α2-grains is faster than the formation of α2-laths in γm-grains. The characteristics of the initial stage of formation were investigated by transmission electron microscopy.

Ab-initio calculations using the Vienna ab-initio simulation package (VASP) were performed for a high Nb bearing γ TiAl based alloy with a composition of Ti-46at.%Al-9at.%Nb in order to evaluate the effect of Nb on the crystal structure. The calculations revealed that upon doping with Nb the resulting structure can have Ti and Nb atoms on Al-sites, which leads to a reduction of the c/a ratio of the tetragonal γ TiAl cell to ~1.In contrast, the c/a ratio is increased, compared to the binary phase, if the Nb atoms occupy solely Ti sites and if Ti antisite defects (i.e. Ti on the Al sublattice) are formed. The relaxed structure models were used to perform high-resolution transmission electron microscopy (HRTEM) and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image simulations. The results showed that the positions of the Nb atoms should be detectable by these high spatial resolution methods, although it might be easier by HAADF-STEM investigations due to the stronger dependence of the signal on the atomic number Z.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Ni, Pd and Cr thin films were grown on (100)SrTiO3 surfaces by molecular beam epitaxy at substrate temperatures of TNJ, pd=650°C and Tcr =150°C. Electron energy-loss spectroscopy (EELS) and high resolution transmission electron microscopy (HRTEM) were applied to investigate the local electronic structure and the atomic structure of the interfaces, respectively. Analytical microscopy was carried out with a parallel energy-loss spectrometer (PEELS766) attached to a dedicated scanning transmission electron microscope (STEM) operated at 100keV, which has a point resolution of 0.22 nm. HRTEM studies were performed on a Jeol JEM ARM 1250 operated at 1250keV (0.12 nm point resolution). Conventional TEM and HRTEM experiments showed epitaxial orientation relationships between the thin metal films and the substrate for each interface.

The electronic structure of the interfaces in terms of the site- and symmetry projected density of states (PDOS) above the Fermi-level can be extracted from the electron energy-loss near-edge structures (ELNES).

The reaction between shape-memory TiNi thin films and silicon has been characterized by conventional, analytical, and high-resolution transmission electron microscopy. A reaction layer is formed during the 525 °C post-deposition crystallization anneal of the sputter-deposited TiNi, and consists of several phases: Ti2Ni, a nickel silicide, and a ternary titanium nickel silicide. The mechanism for the interlayer formation is discussed.