Implanted layers hardness measurement

This friction behaviour has been related to the three-dimensionally cross-linked structure of the ion-irradiated polymer material, since, with increasing fluence, the polymer surface becomes harder and less elastic due to a greater extent of cross-linking. The stick-slip behaviour is thus caused by the adhesion of the two surfaces, and the periodic elastic extension and sudden release of the cross-linked structure of the implanted layer. The microfriction results have been correlated with nanoindentation hardness measurements, which are an indirect measure of the extent of cross-linking (Rao etal, 1995). 

Clearly all indents made with a pyramidal indenter should have the same shape regardless of their size. Thus, since we take pressure used to make this shape to be a measure of hardness—see equations (1.6) and (1.7)—we would expect hardness to be the same and there to be no load effect. Therefore when hardness increases as the applied load decreases, as shown in Figure 1.3, it must be because the volume of material used to yield is smaller and the mechanism for yielding is dependent on a volume term which becomes more significant as the indent size decreases. The most obvious development of this idea is that the shallow near-surface volume of the deformation zone can become a significant fraction of the total affected volume when a very small load is used to make the indent. Thus, work hardened layers, surface compressed layers, ion-implanted layers, and the possibility of chemical reactions between the atmosphere and the surface can dominate the yielding mechanism to produce nonstandard hardness values. Conversely we can say that these phenomena could be studied by measuring the ISE of a ceramic. 

This tutorial will not attempt to deal with aU these ion implantation phenomena, although Mossbauer spectroscopy has been used in aU these fields. We wUl give several illustrative examples but we will mainly focus on semiconductors and to rather low implantation fluences where the implanted atoms are still isolated from each other or just start to coalesce and to form precipitates. The phenomena at high fluences and the dynamics of compound layer formation are beyond the scope of this tutorial. The reason for this limitation is that emission Mossbauer spectroscopy on radioactive probe atoms is particularly powerful in this low concentration range and allows to study the more fundamental phenomena of lattice location and defect association at the individual probe level, which is hard to study with other techniques. On the other hand, experience has shown that one has to be extremely careful in drawing conclusions from Mossbauer spectroscopy results only, as the possible interpretation of a particular Mossbauer spectrum is often not unique. Complementary data, e.g. from electron microscopy. X-ray difiEraction, transport measurements, channelUng experiments, are often more than welcome or even crucial for the interpretation of the hyperfine interaction data. 

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