Quantitative thin film analysis by energy filtering transmission electron microscopy

We have developed novel approaches to extract quantitative information from data obtained with the electron spectroscopic imaging (ESI) technique. The method is based on recording series of energy filtered images across inner shell loss edges and/or in the low loss region. EEL spectra can be extracted out of the image series for each pixel or a given area and can be used for quantification, using the standard EELS techniques. As examples, results obtained for thin layers of titanium on sapphire substrates grown by MBE and for the calcium-content in Si3N4 grain boundary films will be presented and discussed. Using a series of ESI images in the energy range 0–150 eV the thickness of the specimen can be determined using the log-ratio-technique. For specimens with a known geometry it is also possible to determine the inelastic mean free path (MFP) for different materials using (t/Λ)-maps. The accuracy of all techniques can be improved by acquiring the ESI images with hollow-cone illumination (HCI), which reduces artefacts caused by the preservation of elastic scattering contrast.