7 Concluding Discussion

The objectives of the IMPETUS II project is to efficiently simulate the processes that occur in obtaining the results from SIMS or SNMS. The methods described in this paper and reference [4] are employed in the code essentially to return a highly efficient solution. That is to minimise the processing speed whilst ensuring a reasonably accurate and physically acceptable solution of the atomic mixing model.

The code is able to recognise and respond to the material structure that may occur in SIMS and SNMS analysis. If the structure contains wide homogeneous layers then the simulation rapidly progresses. If there are thin layers or sharp interfaces in the mixing window then the finite difference mesh is refined and the simulation progresses more slowly.

In this paper it has been shown how the properties of the mixing equations are taken advantage of to justify the applications of alternative methods in different regions of the material. Although some difficulties in the method - such as a sharp interface in the mixing window or the exact conservation of material - cannot be easily resolved, they have been carefully considered in this paper and the methods finally employed have been justified.

To outcome of this work is a computational method that is able to simulate the SIMS or SNMS processes within a few minutes on a modern personal computer (486 or Pentium). The software also gives a wealth of information on the evolution of the internal material distribution throughout the analysis. The software is therefore a useful analytic tool for the SIMS or SNMS engineer, simulating the experiment within a few minutes and elucidating the underlying processes.