EFTEM imaging

Fig. 2.43. EFTEM images and corresponding line profiles of oxidized AIAs/(AI,Ga)As multilayers.

Figure 10. AIN precipitates with different structures. EFTEM images reveal the cubic phase and the hexagonal phase particles (middle and right). (From J. Microscopy, Bayle-Guillemaud P, Radtke G. and Sennour M., 210 (2003) 66,. with permission from Blackwell Publishing)...

The technique of obtaining images of specific elements, the so-called elemental maps, is another important application in EELS analysis. Energy filtered TEM (EFTEM) images can be obtained with a so-called imaging spectrometer. However, the images are not directly interpretable as chemical maps because of the nonspecific background in the EELS spectrum. 

The image is less sensitive to preserved elastic contrast in the EFTEM images. The ratio cancels out all elastic contrast information that is the same for both pre- and post-edge images. 

Figure 6 EFTEM image partially pasted on a TEM image of a semiconductor test structure showing the different elements present in the specimen as color coded.

The spatial resolution in EFTEM images can be as good as Inm if a careful selection is made of the apertures in the microscope and specimen drift is kept to a minimum. A good understanding of the imaging process is necessary to obtain high-resolution EFTEM images but treatment is beyond the scope of this article. 

Low-energy-loss (<100eV) EFTEM imaging [95,96] is a technique that allows high contrast images and resolution as well as a myriad of possibilities to analyze soft materials. EFTEM can be used to differentiate particles of blends and ESI-TEM to map the polymer filler and interface domains [95]. 

Figure 25.4. TEM and EFTEM images of an iron (III) oxide aerogel/nanometric Al composite. The EFTEM image shows the distribution of iron (III) oxide (green) and aluminum (red) phases and provides a representation of the homogeneous distribution of the two phases.

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