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- 2013 (2) (entfernen)
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- SEM (2) (entfernen)
More and more sub-micro and nano-materials shall be "quickly", but accurately characterized with respect to their morphology, shape, size or size distribution, but also to the chemical composition as well by means of an SEM/EDX (Scanning Electron Microscopy / X-Ray Energy Dispersive Spectrometry) system. This undertaking is becoming successful indeed if the transmission mode at low voltages such as those at a SEM, i. e. mostly up to 30 kV, and EDX, respectively is employed. The transmission mode at conventional SEM can e "activated" firstly by re-defining the specimen to be analyzed and preparing it as a thin specimen, which is quasi-transparent to electrons and by finding a way of collecting only the transmitted electrons for analysis. The first issue can be easily realized by using the conventional TEM grids (and the respective sample preparation); the second one becomes feasible either (i) by placing a socalled STEM semiconductor detector directly under the thin specimen or (ii) by using a Special transmission set-up, which enables to the conventional Everhart-Thornley detector to collect only transmitted electrons by blocking the direct collection of secondary electrons and guiding only the transmitted electrons onto it.
Potential candidates of reference nano-materials are manufactured and systematically characterized in particular with respect to their morphology (shape, size and size distribution) in the frame of the running large European project NanoValid. By exploiting the transmission operation mode in a SEM, known as T-SEM, it is demonstrated by means of three representative examples of nanoparticles how a quick morphological inspection up to a complete, metrological characterization is feasible.