Tomo-STEM

Figure 3.19. The first generation tomo-STEM stage for the new electron tomography technique combining STEM and ESEM.

Figure 3.20. Some examples of reconstructed volumes after characterization with tomo-STEM (a) SiC nanowires grown on a tungsten tip (b) impact-resistant poly(vinyl chloride) (volume sizes 41 32 40 pm3 and 4.2 4.8 0.8 pm3, respectively).

The main drawbacks of this approach are the low availability of such instruments in laboratories, and the fact that many samples are sensitive to ion beam damage, require specific preparation (95), and can induce low contrast. Moreover, the imaging between two milling periods is typically performed in the backscattered electrons mode, which is not always favorable this is the case for carbon nanotubes in a polymer matrix as the atomic number contrast is low. This is probably the reason why, even if the FIB/SEM approach is used on polymer nanocomposites, it not used in the literature for carbon nanotubes in polymer matrix. In this last application, the tomo-STEM technique is a good alternative to obtain images of relatively thick samples with high contrast and resolution (91). 

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