NANOANALYSIS OF MATERIALS BY MEANS OF EELS SPECTRUM IMAGING IN A TRANSMISSION ELCTRON MICROSCOPE

Werner Grogger, Ferdinand Hofer, Gerald Kothleitner, Bernhard Schaffer
Institute for Electron Microscopy and Fine Structure Research, Graz University of Technology, Steyrergasse 17, A-8010 Graz, Austria

The characterisation of nanostructured devices and functional materials at a nanometre scale is paramount for the understanding of the physical and/or chemical properties. With recent progress in electron energy-loss spectroscopy (EELS) using a monochromated transmission electron microscope (TEM) it becomes now possible to solve advanced materials science problems which have not been accessible before. In particular, one can obtain improved information not only about the local chemical composition of a sample [1], but also about chemical bonding [2] and physical properties [3]. Advances in EELS spectrum imaging, i.e. the collection of EELS data along the spatial and the energy-loss dimensions has progressed to the point, where sophisticated spectrum image data processing now can be carried out routinely. This became possible with the advent of combined spectral aberration-, energy- and spatial drift corrections schemes, carried out simultaneously, giving access to high quality spectrum images [3]. In the presentation we will focus on practical aspects and applications of spectrum imaging by means of energy-filtered TEM (EFTEM). The advantages of EELS and EFTEM spectrum imaging and its extended mapping capabilities will be demonstrated using typical materials science examples. In the first case, nanometre sized precipitates in a Cr-steel have been analysed using inner-shell ionisation edges. Furthermore, the interfaces between organic and inorganic layers in organic optoelectronic devices and in multilayered ceramics and semiconductors are investigated using the low-loss region of the EELS spectrum.

[1] F. Hofer, P. Warbichler, in "Transmission Electron Energy Loss Spectrometry in Materials Science", ed. C.C.Ahn, VCH-Wiley, New York (2004) pp.181-233.
[2] C. Mitterbauer et al., Ultramicroscopy 96 (2003) 469.
[3] B. Schaffer et al., Ultramicroscopy 106 (2006) 1129.