Speaker
François Schiettekatte
(U)
Description
Ion beam analysis techniques are usually based on the approximation that the ions cross the sample in straight line down to a certain depth, where they suffer a major collision, and either the ion itself, its collision partner or another product of the collision emerge from the sample, also following a straight line trajectory. This approximation becomes increasingly poor with decreasing ion energy, heavy ions and increasing distance travelled in materials, since the probability of collision increases. The first two are conditions often met when trying to improve the resolution of the techniques. In order to take into account the effect of more than one collision, simulation programs that are based on analytical formula to simulate the measured spectrum can consider the effect of two important collisions, but in some cases, this is not sufficient.
In this presentation, we show how a simulation computing the trajectory of each ion can indeed reproduce accurately the effects of multiple scattering (MS) is most problematic situations. Examples include heavy-ion Rutherford backscattering spectrometry (HI-RBS) and elastic recoil detection (HI-ERD), where MS contributes to an important background, and in coincidence analysis, where is affects the detection efficiency in a way that required detailed analysis of the trajectories. In that case, simulations show how MS “de-correlates” the two ions leaving the collision site.
