Ordering effects in extreme high-resolution depth profiling with MeV ion beams

The continuing development of depth profiling with MeV ion beam methods with depth resolutions in the nanometre, and even sub-nanometre, regime implies the resolved depth become comparable with the interatomic spacing. To investigate how short-range ordering influences depth profiles at these resolutions, we have employed a mathematical modelling approach. The radial, g(r) and depth distribution, g(z) functions were calculated for (1 0 0) surface, random and amorphous Si structures at 300 K produced using molecular dynamics simulations with the EDIP quasi-empirical potential. The results showed that short-range ordering lead to reduction of the scattering yield below the deep asymptotic level within about half a interatomic distance which will give a perturbation of the scattering yield for Rutherford Backscattering Spectrometry (RBS) and glancing incidence Elastic Recoil Detection Analysis (ERDA) geometries.