Below 100 Nanometer Resolution

As mentioned in Section 2.10.3.1, the resolution of SEM (Figure 2.26) is about 1 pm. Thus, the size of enrichments greater than 1 pm can be measured by SEM. When smaller spots of lead enrichments are found, their size should be determined by another method below 1 pm resolution. For example, atomic force microscopy (AFM) can be a suitable method since it has nanometer resolution. This technique,... 

A shortcoming of both NRA and SIMS is that the spatial resolution is not high in all three directions. While depth resolutions on the order of a few hundred nanometers or less are routine, the profiles are measured over surface areas of a few hundred square micrometers or even millimeters. Thus, the concentration profile can be an average from various localized reaction or fast diffusion (e.g. pipe diffusion). The consequences of dual-diffusion mechanisms on the geometry of isotopic profiles is discussed in more detail below. There is no available method to by pass these problems for isotopic diffusion, although for elemental diffusion, alytical Transmission Electron Microscopy (ATEM) offers an alternative (Meissner et al. 1997). 

Apart from these four main techniques there are many other techniques but their applicability is often limited to some elements. MAS-NMR technique turns out to be very useful for determining if non zero nuclear spin elements are incorporated into the lattice because of its sensitivity to local environment symmetry. Also in favorable cases techniques as Mossbauer, diffuse reflectance UV-Vis and ESR spectroscopies are very helpful while high resolution electron micrographs and simulated imaging are of great interest (38) with in addition the possibility of specific chemical analysis at nanometer scale by EDX-STEM. At last XPS may be informative to determine if surface and bulk compositions are identical or not, although the technique by definition is only sensitive to the first top layers (1 to 2 nm) while zeolitic features concern the whole material. Some examples will be given below. 

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