Sputtering composition changes

Figure 9.15. Influence of sample cleaning on XPS scans taken on a thin-film superconductor, (a) Survey scan from an as-received surface, (b) Survey scan from surface after ion-beam (sputter) cleaning. Note the reduction in the Cls peak after cleaning, (c) Comparative Ba3d scans from both cases. Note the change in shape and size as the surface contaminant layers (probably containing carbonates and hydroxides of Ba in addition to other components) are removed. The peak shapes and intensities of other cations change, too. Initial data represent the composition and chemistry of the contaminant layer, whereas that from sputtered sample represents those of the pure underlying superconductor (possibly with sputter-induced changes that need to be accounted for).

In many systems, composition changes extend to a depth comparable to the range of the ion used for sputtering. The composition reaches a steady state after an amount of material comparable to the thickness of the altered surface layer has been sputter-removed. The steady-state surface composition is independent of the mass and energy of the sputtering ion. Composition depth profiles have been... 

The surface chemical composition of brown coal ash particles formed during combustion has been determined by Ersez and Liesegang (1991) to detect any sputter-induced composition changes or to observe any difference between the surface and bulk compositions of the ash. They have observed that certain steels used for heat exchanger piping may well be predisposed to aluminosilicate fouling due to their intrinsic A1 content. 

Further improvements resulted from the use of a probe for sonication.325 Jhe higher reactivity seems not to be due to an increased surface area, but rather to morphological and composition changes, as evidenced by electron microscopy and sputtered neutral mass spectrometry.i< When applied to ethyl bromo propionate and trifluoroacetaldehyde, the resulting p-hydroxy esters are obtained in good yields with predominance of the threo isomer.272... 

Each of these combinations of materials can be considered composites on a microscale. Ceramic composites, which can be considered composites on a macroscopic scale, include laminated structures and composites that have been termed functionally gradient materials (FGMs). FGMs, which are designed to have smooth gradients in composition, have been fabricated by vapor deposition, plasma sputtering, and electrodeposition techniques. Lamination techniques are used for FGM applications in which more abrupt compositional changes are acceptable. 

When all of the ISS spectra are plotted in a three-dimensional manner, such as the z- plot shown in Figure 3, the changes in surface composition with depth are much more obvious. In this figure, each spectrum represents the composition at a different cross section of the total depth sputtered, hence the spectra are plotted at different depths. Note that the spectra are not recorded at identical incremental depths. 

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