Electron Microscopy XIV

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Authors: Wolfgang Neumann, Holm Kirmse, Ines Häusler, Corinna Grosse, Peter Moeck, Sergei Rouvimov, Matt Beekman, Ryan Atkins, David C. Johnson, Kerstin Volz
Abstract: Abstract. New methods of electron crystallography, particularly modern methods of electron diffraction have opened new strategies for the structure analysis of nanostructured materials and materials systems. The possibilities and limitations of the combined use of electron crystallography methods will be demonstrated for a semi-automatic orientation determination of MnAs clusters in a GaAs matrix and structural investigations of ferecrystals.
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Authors: János L. Lábár, Ákos K. Kiss, Silke Christiansen, Fritz Falk
Abstract: A method is presented here for complete geometrical characterization of grain boundaries, based on measurement of thin films in the TEM. First, the three parameters, characterizing the misorientation of the two neighboring grains are determined from convergent beam electron diffraction (CBED). Next, the last two (of the total five macroscopic degrees of freedom) parameters are determined from bright field (BF) images to describe the orientation of the boundary plane between them. Ambiguity in the tilt direction of the plane is resolved from BF images recorded at two distinct goniometer settings. Application of the method is demonstrated in Silicon thin films. GB-plane distribution in a thin film is not necessarily identical to the distribution of similar planes in bulk materials. It was observed in low dimensional fcc metals (wires or thin films) that energy minimization of GBs can follow two (mainly alternative) routes. Either low energy planes (like {111}) are formed in 3 boundaries, or alternatively, it is observed that the GB plane has a general index (and high energy density) but it ends at both free surfaces of the sample, resulting in a GB, almost normal to the sample surface, minimizing the total area of the GB. We observed that this later type of planes is mainly characteristic of non-3 boundaries in thin Si films, crystallized from melt on glass substrates (separated by a thin SiN barrier layer). This observation is important for the expected recombination properties of the multicrystalline Si (m-Si) in planned solar cell (SC) applications.
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Authors: Edgar F. Rauch, Muriel Véron, Stavros Nicolopoulos, Daniel Bultreys
Abstract: EBSD is a well known technique that allows orientation and phase mapping using an SEM. Although the technique is very powerful, has serious limitations related with a) special resolution limited to 50 nm (SEM-FEG) and b) specimen preparation issues as is not possible to obtain EBSD signal from rough surfaces or strained materials , nanoparticles etc.. To address those difficulties , a novel technique has been developed recently (EBSD-TEM like) allowing automatic orientation and phase mapping using template matching analysis of acquired diffraction patterns in TEM. Electron beam is scanned through the sample area of interest ; the acquired electron diffraction patterns from several sample locations are compared via cross-correlation matching techniques with pre-calculted simulated templates to reveal local crystal orientation and phases. The dedicated device (ASTAR) allows orientation and phase identification of crystallographic orientation in a region of interest up to 10µm2, with a step size ranging from 1nm to 20nm depending on the transmission electron microscope setting (FEG or LaB6).
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Authors: Elżbieta Jezierska
Abstract: The antiphase domain structure in Ni3Al and Al3Ti+Cu intermetallic alloys was recognized by conventional transmission electron microscopy and large angle convergent beam electron diffraction methods. In the case of antiphase boundary the superlattice excess line is split into two lines with equal intensity on bright and dark field LACBED pattern. This splitting can be considered as typical and used to identify APBs. The recognition between perfect structure of the defect-free matrix and the screw deviation around the nanopipes in GaN epilayers was performed with high accuracy using Zone Axis LACBED images.
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Authors: Mariusz Płuska, Andrzej Czerwiński, Jacek Ratajczak, Anna Szerling, Jerzy Kątcki
Abstract: Cathodoluminescence (CL) in SEM and electroluminescence (EL) techniques are widely used for investigation of optical properties of electronic structures. It is assumed that the CL signal represents the local properties of the region irradiated by the electron beam. However, this assumption is true if there is no electric field in the excitation region. In the opposite case the electron-hole pairs generated by the electron beam are separated by the electric field and the local voltage source is generated. The voltage is distributed all over the structure through resistance paths and it causes a current flow, which presence affects the registered CL signal. A range of this effect depends on the resistance distribution within the structure and on the value of electron beam current. The range may be much longer than the diffusion length of minority carriers. When EL signal is measured in SEM, it represents the mean properties of the whole structure. The comparison of the CL results with the EL ones detected in SEM gives valuable information about the examined structures, as will be shown in the present investigations. The AlGaAs/GaAs heterostructures with 8 nm InGaAs quantum well have been examined. For that aim also special test structures for CL and EL measurements have been formed on standard epitaxial structures.
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Authors: Witold Słówko, Michał Krysztof
Abstract: To extend capabilities of classic instruments toward the VP/E technique, authors designed the vacuum-detector system in the form of a simple attachment, which can be mounted to a classic SEM, without changes in its original structure. The main part of the system is the vacuum and detection head, combining the intermediate chamber and electron detectors of chosen kinds. Authors investigate the SE detector showing the unipotential lens structure to find optimum solution for a wide range of gas pressures from high vacuum to pressures exceeding 10 mbar.
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Authors: Susanne Richter, Klaus Riediger, Angelika Nester
Abstract: Food supplements play an increasing role in the nanofood market because improvement of effectiveness and efficiency of delivery of bioactive compounds is presumed. An electron microscopic method based on the international Standard ISO 13322-1:2004 was developed for controlling and documenting size, size distribution, surface structure, shape and aggregation state of mineralized food supplement particles. For particle size distribution, a combination of conventional TEM- and SEM-methods, which allows identifying the size distribution of the whole product, is described.
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Authors: Justyna Płoszaj, Ewa Talik, Zofia Piotrowska-Seget, Józef S. Pastuszka
Abstract: The paper presents the research results of the airborne bacteria collected at the wastewater treatment plants working with activated sludge system. Samples were taken by a six-stage Andersen Impactor placed near the aeration chambers. Bacteria cought at Petri plates were incubated at room temperature for 4 days, then analyzed in a macroscopic and microscopic way. This initial investigation was aimed at morphological characteristics of colonies and breeding characteristics of particular strains to giver general overwiev. Bacteria were identified on the basis of their metabolic properties using API biochemical tests. The essential studies were carried out using JOEL scanning electron microscope (FE-SEM model with field gun 7600[F]), equipped with "Cryo-SEM”, which gives the possibility of testing delicate biological samples in a frozen state. Its high resolving power and large depth of field allows to obtain images of surface structure of microorganisms in a magnification range from 1 000x to 70 000x. Bacteria samples were analyzed also in a fructured state what revealed internal structes and the thickness of cell walls which was in the range of 0,080-0,180 [μm]. Moreover, elemental composition of the surface layer of bacterial was also examined using photoelectron spectroscopy (XPS). Dominant elements were carbon, oxygen and nitrogen. Analysis of main line (C1s, O1s, N1s) allowed the identification of chemical composition of studied bioaerosols. Investigation found that the main compounds were polymers such as peptides and polysaccharides, as well hydrocarbon like compounds.
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Authors: Adam Kruk, Beata Dubiel, Aleksandra Czyrska-Filemonowicz
Abstract: TEM, HAADF-STEM tomography and FIB/SEM tomography studies have been carried out to visualize three-dimensional morphology of the oxide dispersoids in ferritic ODS alloy INCOLOY MA956. Electron tomography results provided quantitative data about particle shape, size and distribution of the particles, complementary to those obtained by means of quantitative TEM metallography. It was shown that FIB/SEM, a meso-scale tomography technique, is suitable for 3D reconstruction of the objects of 100 nm in size or even smaller.
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