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Electron Microscopy Overview Introduction The ultimate goal of electron microscopy is to identify and determine the position, chemical state and local electron density for each atom in a material in all three dimensions. This is not possible yet, and in many cases such detailed analysis is not of practical interest. However, access to quantitatively interpretable information on an appropriate length scale (for nanotechnology from ~0.1 nm to few hundreds of nm) has major impact on scientific understanding and the development of new nanomaterials and their applications. Electron microscopy provides access to such information. An EM image should be viewed as a matrix of quantitative measured data rather than a mere photo. The data can, through suitable processing, yield quantitative information. The data acquired on a well-characterized, understood and carefully operated and maintained instrument can provide deep insights to scientific problems and result in new commercial materials and applications. The goal of the Electron Microscopy (EM) research group is to achieve and maintain world leadership and reputation in aspects of electron microscopy of interest to the NINT research community and industrial partners. EM must also continuously attract a wide range of external multidisciplinary collaborations in order to develop into a hub of EM research activities. To achieve this goal, NINT’s EM Group has electron microscopy instrumentation and expertise that are at the cutting edge. Strategy Our EM research focuses on specific areas of electron microscopy that present unique opportunities for NINT. We start with highly flexible instrumentation with many unique features and invest significant intellectual effort in developing new techniques and broadening the understanding of physical principles EM experiments. In addition to its unique features, our EM instrumentation is designed to ensure that routine techniques can be performed at the highest level. Our Facilities and Instrumentation The electron microscopy facility at NINT will be housed in an ultra-quiet space in our purpose-built building. The facility features two transmission electron microscopes (TEM) and two scanning electron microscopes (SEM), as well as sample preparation and computer/data processing support. The transmission electron microscopes are located in a characterization suite with extremely low electromagnetic disturbances, temperature variations and mechanical vibrations. Research Areas Quantitative electron energy loss spectroscopy (EELS) Primary electrons inelastically scattered by the sample carry a wealth of information encoded in the energy loss spectra. The highly localized nature of many of these interactions, together with the ability to focus the electron probe to less than 0.2 nm, guarantees high spatial resolution of the measurements. From the wide variety of information accessible by EELS, NINT focuses on core-loss spectroscopy, which provides quantitative information on local chemical composition (from edge intensities) and local chemical bonding (near edge fine structure - ELNES). Interpretation of ELNES often relies on fingerprinting (comparison to spectra of known materials). Our EM group is working to improve the interpretation of the ELNES signal. We are also working on techniques that make use of the dependence of fine structure on crystallographic orientation to obtain and interpret detailed information on studied materials. Ultra high energy resolution (sub 0.1 eV) low loss EELS are being pursued to a lesser extent. For experiments where ultra high energy resolution is needed, we collaborate with Prof. Botton's group at McMaster University to make use of their monochromated TEM.
Electron interferometry (EI) The new, highly stable, TEMs with high brightness electron source provide an opportunity to study of quantum phenomena exhibited by electrons. Although scientifically interesting, practical applications are more likely to come from the ability to quantitatively measure both the amplitude and the phase of an electron wave. Measuring both phase and amplitude of the electron wave allows us to obtain complete information on the elastic interactions of the beam with the sample. EI allows quantitative measurement of electrostatic and magnetic potentials at a resolution not achieved by any other technique. Furthermore EI has the potential to reduce the dose needed for imaging, an important advantage for imaging radiation sensitive materials such as organic nanostructures and catalysts. Scanning Electron Microscopy (SEM) SEM characterization is a typically qualitative technique. In most cases, two images, even if taken in the same session, cannot be compared in a quantitative manner. Only a few techniques (EDX, EBSD) allow for semi-quantitative measurements. The goal of SEM development at NINT is to work toward semi-quantitative SEM characterization. | 
