Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5466770 | Ultramicroscopy | 2017 | 7 Pages |
Abstract
In this experimental work we present novel methods to increase the spatial resolution of valence electron energy loss spectrometry (VEELS) investigations below the limit given by the inelastic delocalization. For this purpose we analyse a layer stack consisting of silicon/silicon-oxide/silicon-nitride/silicon-oxide/silicon (SONOS) with varying layer thickness down to the 2Â nm level. Using a combination of a conical illumination and energy filtered transmission electron microscopy we are able to identify the layers by using low energy losses. Employing Bessel beams we demonstrate that VEELS can be performed in dark-field conditions while simultaneously the Bessel beam increases the spatial resolution of the elastic image due to less sensitivity to the spherical aberration of the condenser lens system. The dark-field conditions also guarantee that only electrons are collected that have neither undergone an energy loss being due to the CËerenkov effect, nor due to the excitation of transition radiation or light guiding modes. We consequently are able to measure the optical properties of a 2.5Â nm thin oxide being sandwiched by the silicon substrate and a silicon-nitride layer.
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Physical Sciences and Engineering
Materials Science
Nanotechnology
Authors
Michael Stöger-Pollach, Thomas Schachinger, Kati Biedermann, Volkhard Beyer,