Composites electron beam damage

AES is a useful element-specific technique for quantitative determination of the elemental composition of a surface. Although some chemical information is available in principle, the technique is used largely for elemental analysis. Electron beam damage can decompose organic adsorbates and cause damage, particularly on insulating surfaces. In some cases, the beam can reduce metal oxides. 

Unlike AES in which, especially for insulating samples, electron beam damage may occur, the damage to the sample in XPS is minimal. Furthermore, electrostatic charging of commonly insulating ceramic powders is not a severe problem. AES and XPS provide similar information about the elemental composition, and the methods tend to be complementary rather than competitive. It is... 

Before discussing the diffusion of the homopolymer chains into the copolymer structure it is important to discuss the bulk and surface properties of the copolymers. The bulk characterization was accomplished using small-angle X-ray scattering (SAXS). Ideally, electron microscopy (EM) measurements should be done but preliminary studies were unsuccessful because of considerable electron beam damage to the PMMA. The surface characterization was done using X-ray photoelectron spectroscopy (XPS). This technique is more usefull for determining surface compositions than EM. 

N and 0, in solid material. The second point is that EXELFS is especially suitable for the study of inhomogeneous samples (structurally and compositionally heterogeneous in the sense discussed in section 2.2 above) because the primary electron beam can be focussed to a diameter of ca 20. Other advantages of EXELFS have been discussed elsewhere (60, 61). The limitations of the technique include (i) the need to select an optimal thickness of sample so as to minimize multiple scattering and (ii) the susceptibility of the samples to suffer radiation damage. 

With direct observation, the sample must be kept cold in the electron microscope, and care is required to prevent sample damage in the beam and to prevent microscope contamination. In addition, these frozen samples are often difficult to image because of charging effects that distort the image. The benefit of this extra care in sample handling, however, is that electron beam interactions with the sample produce characteristic X-ray signals that allow identification of components of the emulsion being observed. This technique has been refined to the point where, in special cases, chemical compositional differences at the emulsion interface can be identified, as well as the composition of the dispersed and continuous phases 109, 110),... 

Since the electron beam can be moved across die surface, it is possible to measure a concentration profile along a line or to generate figures. A disadvantage is the relatively low sensitivity and damage to the sample. AES is mainly suited to the determination of surface composition and changes therein. 

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