Appendix G - Implantation metallurgy – study of equilibrium alloys

Summary

Study of metallurgical phenomena

Ion implantation is a powerful tool, useful in the study of alloying phenomena in metals, but the technique has been exploited in that capacity by only a few researchers. The following discussion, taken from the work of S. M. Myers, gives examples of its use for this purpose. Myers (1980) was one of the first to fully utilize ion implantation to study metallurgical phenomena.

The as-implanted ‘surface’ alloy is often metastable on the basis of extended solubilities, as discussed in Chapter 10. Upon heating, the implanted structure returns to an equilibrium situation, and the tracing of this evolution to equilibrium serves to help determine properties such as diffusion rates, solid solubilities, and solute trapping. The study of this transition can be aided by the use of ion beam analysis methods, as well as by conventional electron microscopy, as described below. Myers outlines the evolution of the ion implanted depth distribution and the formalism required to extract the pertinent solid state parameters from the analysis; his approach is paraphrased below.

Diffusion and the composition profile

The quantitative determination of metallurgical properties relies principally on analysis of the time-dependent composition profile obtained during annealing. This analysis involves certain approximations, depending upon the particular experiment, and Myers has outlined the mathematics for certain specific cases, assuming the host to be semi-infinite. The evolution of the implanted distribution during thermal annealing, performed after the implantation has been completed, is of greatest interest.