CAICISS Analysis Methods
An inspection of the data acquired using low energy ion scattering techniques can be used to make qualitative statements on the crystalline structure under investigation, such as elemental identification and crystallographic symmetry directions. However, a quantitative description of the atomic structure and elemental composition of the surface region can only be obtained via a comparison with data generated using computational simulation methods. This is the only viable option for including accurate ion-atom interaction potentials, lattice vibrations, multiple scattering and other effects in the analysis of low energy ion scattering data.
FAN backscattering simulation code
The FAN simulation code is a break from the traditional Monte Carlo methods, such as MARLOWE, previously used for the simulation of low energy ion scattering experiments. Suited to the study of backscattered particles, the FAN code performs simulations by generating a fan of possible incident and outgoing trajectories for each atom in the simulated crystal structure. These trajectories are then summed over all atoms to give a CAICISS-like spectrum for each element in the trial structure. Using an in-house optimisation routine FAN can be used to determine the atomic structure and elemental composition of the surface region in a layer-by-layer fashion.
The FAN code, originally developed by Horst Niehus in Berlin, can be dowloaded here.
A fan of outgoing trajectories following scattering from a third layer atom in a Cu-Au alloy structure. Au atoms are shown in white, Cu in red.
Kalypso molecular dynamics simulation
Recently we have begun a project to validate the use of the more simple FAN code by comparing it to results generated by a molecular dynamics simulation for the same crystal and beam parameters. The Kalypso code, developed by Marcus Karolewski, is being used for this purpose. More details on the package and how to download it can be obtained here.
