Imaging in SEM

An image from SEM represents only the property of a surface and not the internal stracture that is visible with a TEM image. The process of generating an image in SEM is slower than that in TEM. The SEM cannot be used to study detailed stracture of nanocomposites because it has a poorer resolution as compared to TEM. Therefore, SEM analysis should always be used in combination with other microscopic techniques such as TEM or AFM. 

Figure Bl.19.32. AFM image of Blue Seript II plasmid (400 mu x 400 mu) in propanol, taken with super tip , prepared by earbon deposition on nomral tip in SEM, followed by ion milling. (Taken from [152], figure 1.)...

Instmmentation for tern is somewhat similar to that for sem however, because of the need to keep the sample surface as clean as possible throughout the analysis to avoid imaging surface contamination as opposed to the sample surface itself, ultrahigh vacuum conditions (ca 10 -10 Pa) are needed in the sample area of the microscope. Electron sources in tern are similar to those used in sem, although primary electron beam energies needed for effective tern are higher, typically on the order of ca 100 keV. 

Electron Probe Microanalysis, EPMA, as performed in an electron microprobe combines EDS and WDX to give quantitative compositional analysis in the reflection mode from solid surfaces together with the morphological imaging of SEM. The spatial resolution is restricted by the interaction volume below the surface, varying from about 0.2 pm to 5 pm. Flat samples are needed for the best quantitative accuracy. Compositional mapping over a 100 x 100 micron area can be done in 15 minutes for major components Z> 11), several hours for minor components, and about 10 hours for trace elements. 

With a special optical system at the sample chamber, combined with an imagir system at the detector end, it is possible to construct two-dimensional images of the sample displayed in the emission of a selected Raman line. By imaging from their characteristic Raman lines, it is possible to map individual phases in the multiphase sample however, Raman images, unlike SEM and electron microprobe images, have not proved sufficiently useful to justify the substantial cost of imaging optical systems. 

The Raman images in Figure 7 show that PTFE clusters in the sample are between 8 and 20 pm in diameter [46]. These results have also been confirmed by FTIR imaging and SEM [47]. 

Beneath the outer polyester layer is a white opaque layer, labeled "2" in Figure 63, which was identified as polyethylene. The polyethylene layer shows features that are characteristic of brittle failure. The direction of applied stress during failure was likely in the vertical direction in the SEM images in Figure 63. 

The condensation chemistry allows films of various compositions, as the addition of sulfate renders the materials amorphous over a range of concentrations as implied by the acronym HafSOx, where x typically assumes values of 0.3-1 (refer to Fig. 4.3, where the top reaction sequence represents x = 0.5.) The amorphous character and structural integrity are retained until the material decomposes with stoichiometric loss of S03(g) at approximately 700 °C. The smoothness and uniformity of deposited films are illustrated by the Scanning electron microscope (SEM) images in Fig. 4.4. Rapid kinetics, absence of organics, and facile condensation all play important roles in the deposition of these dense HafSOx films. 

SEM micrograph depicting 0.1 Sum imaging in GMC with a schematic representation of GMC chemistry. 

In SEM, the surface of the polymeric surface is scanned using an electron beam with the reflected or backscattered beam of electrons collected and displayed on a cathode ray tube screen. The image represents the surface contour of the scanned material. Because the surface must be conductive, most polymer surfaces must be overlaid with a conductive coating. Magnifications up to about 50,000 are carried out using SEM. 

Fig. 3 shows a conceptual example of the possibilities offered from structuring the surface of oxides in terms of array of Ti02 nanotubes which can be viewed as an ensemble of nanoreactors. The SEM image in the inset of Fig. 3 shows an example of the Ti02 nanostructures obtained in the case of anodic oxidation of titanium foils. ... 

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