[en] Collimator settings and performance are key parameters for deciding the reach in intensity and β* in order to conclude on possible limits for the 2012 run, a summary is first given of the relevant running experience in 2011 and the collimation-related MDs. These include among others tight collimator settings, a quench test, and aperture measurements. Based on the 2011 experience, we conclude on possible running scenarios for 2012 in terms of collimator settings, intensity and β* from the collimation point of view. (authors)

[en] A very simple tomography sample holder at minimal cost was developed in-house. The holder is based on a JEOL single tilt fast exchange sample holder where its exchangeable tip was modified to allow high angle degree tilt. The shape of the tip was designed to retain mechanical stability while minimising the lateral size of the tip. The sample can be mounted on as for a standard 3mm Cu grids as well as semi-circular grids from FIB sample preparation. Applications of the holder on different sample systems are shown. (paper)

[en] UV-Laser technology is one of the most challenging and important areas in nitride semiconductor research. A new growth technology, using a thin GaN interlayer approach, has recently been developed for UV-LEDs in our department. Improved optical quality of so grown LEDs has been demonstrated. A similar growth approach has now been used to grow an UV-laser structure that has shown stimulated emission (lasing) at ∼340 nm via optical pumping. We report here a study of the microstructure, the epitaxial quality and the elemental distributions of such an aluminium gallium nitride-based heterostructure using a combination of various electron microscopy techniques.

[en] Collimator settings and available aperture are key parameters for deciding the reach in intensity and β*. In order to conclude on possible limits for the 2012 run, a summary is first given of the relevant running experience in 2011 and the collimation-related MDs. These include among others tight collimator settings, a quench test, and aperture measurements. Based on the 2011 experience, we conclude on possible running scenarios for 2012 in terms of collimator settings, intensity and β* from the collimation point of view

[en] Nanoparticles are used in industry for personal care products and the preparation of food. In the latter application, their functions include the prevention of microbes' growth, increase of the foods nutritional value and sensory quality. EU regulations require a risk assessment of the nanoparticles used in foods and food contact materials before the products can reach the market. However, availability of validated analytical methodologies for detection and characterisation of the nanoparticles in food hampers appropriate risk assessment. As part of a research on the evaluation of the methods for screening and quantification of Ag nanoparticles in meat we have tested a new TEM sample preparation alternative to resin embedding and cryo-sectioning. Energy filtered TEM analysis was applied to evaluate thickness and the uniformity of thin meat layers acquired at increasing input of the sample demonstrating that the protocols used ensured good stability under the electron beam, reliable sample concentration and reproducibility

[en] A procedure to quantify annular dark field (ADF) images in scanning transmission electron microscopy (STEM) has been applied to two 200kV transmission electron microscopes (TEMs), a JEOL 2010F and a double aberration-corrected JEOL 2200FSC. A series of ADF images is acquired as a function of the camera length (i.e. inner detection angle). Then the intensity ratio of InGaAs and GaAs is plotted vs. camera length and extrapolated to zero, at which point the contrast behaves exactly as predicted by Rutherford's scattering. The linearity of ADF intensity ratio vs. camera length improves significantly by using the JEOL 2200FSC compared to the JEOL 2010F at medium resolution. A high-resolution ADF image at 2MX nominal magnification acquired in the JEOL 2200FSC shows the same linearity of intensity ratio vs. camera length, independent of whether the ratios of the average background intensities or the fringe amplitudes are used for the analysis. This is explained by both group III and group V atoms contributing to the {111} fringes observed, similar to low resolution data.

[en] Ge/GaAs heterostructure research is largely motivated by the application of this material in solar cells, metal-oxide-semiconductor field-effect transistors, mm-wave mixer diodes, temperature sensors and photodetectors. Therefore, understanding of how the properties of Ge/GaAs heterostructure depend on its preparation (growth) is of importance for various high-efficiency devices. In this work, by using thermal Ge evaporation on GaAs(100), we studied structural properties of these films as a function of the deposition rate. Film grains size and morphology show strong dependence of the deposition rate. Low deposition rates results in films with large crystal grains and rough surface. At high deposition rates films become flatter and their crystal grains size decreases, while at very high deposition rates films become amorphous. Cross-sectional TEM of the films show that the Ge films are granular single crystal epitaxially grown on GaAs. The Ge/GaAs interface is atomically abrupt and free from misfit dislocations. Stacking faults along the [111] directions that originate at the interface were also observed. Finally by using the Kelvin probe microscopy we show that work function changes are related to the grain structure of the film.

[en] We have prepared polycrystalline Co₂FeSi thin films on a number of seed layers to optimize their structural and magnetic properties. Using a Cr/Ag combined seed layer, films have been produced with extremely low interfacial roughness (<1 nm) and controllable coercivities in the range 12–27 Oe. Such a structure would be suitable for the free layer in a spintronic device. Using a NiCr seed layer and IrMn as an antiferromagnetic layer a small exchange bias of ∼30 Oe has been achieved. However the use of a 0.5 nm Mn layer at the IrMn/Co₂FeSi interface increases the exchange bias (H_ex) to 375 Oe after annealing. This structure would be suitable for the pinned layer in a spintronic device. (paper)

[en] Nano-structured alloyed materials have been demonstrated with a large improvement of their thermoelectric properties. These improvements have been obtained by tailoring a reduction in the material thermal conductivity. However, such improvements have not yet been demonstrated for bulk materials. Recently, a new approach based on phonon scattering theory has been successfully applied to bulk materials. In this approach, nanoparticles are embedded in a hosting matrix and act as multi-scale phonon scattering centres providing a reduction in the material thermal conductivity. In this work, {CoSi₂ (nanoparticle): SiGe (host)} nanocomposite thermoelectric materials and their precursors for the synthesis were investigated. The purpose of the investigation is to understand the inherent interactions of the nanoparticles with the support material

[en] Dilute (III, Mn)V ferromagnetic magnetic semiconductors have potential applications in spintronic devices as magnetic field sensors, spin transistors and reconfigurable logic devices. For such applications ferromagnetism at room temperature is a practical requirement. Previous work has shown that In_1-xMn_xSb films grown on GaAs (100) substrates by atmospheric pressure metalorganic vapour phase epitaxy were single phase and had high temperature ferromagnetism for Mn concentrations up to 2%. Here we present a study of InMnSb thin films at higher Mn concentration (10 at%) showing ferromagnetic properties at room temperature. Aberration corrected and analytical (scanning) transmission electron microscopy techniques were used to study the structure and elemental distribution of the In_1-xMn_xSb/GaAs system. The crystalline quality of the film and the presence of phase separation is evaluated in the context of a cluster-mediated ferromagnetism model.