Shower approach in the simulation of ion scattering from solids

Abstract

An efficient approach for the simulation of ion scattering from solids is proposed. For every encountered atom, we take multiple samples of its thermal displacements among those which result in scattering with high probability to finally reach the detector. As a result, the detector is illuminated by intensive "showers," where each event of detection must be weighted according to the actual probability of the atom displacement. The computational cost of such simulation is orders of magnitude lower than in the direct approach, and a comprehensive analysis of multiple and plural scattering effects becomes possible. We use this method for two purposes. First, the accuracy of the approximate approaches, developed mainly for ion-beam structural analysis, is verified. Second, the possibility to reproduce a wide class of experimental conditions is used to analyze some basic features of ion-solid collisions: the role of double violent collisions in low-energy ion scattering; the origin of the "surface peak" in scattering from amorphous samples; the low-energy tail in the energy spectra of scattered medium-energy ions due to plural scattering; and the degradation of blocking patterns in two-dimensional angular distributions with increasing depth of scattering. As an example of simulation for ions of MeV energies, we verify the time reversibility for channeling and blocking of 1-MeV protons in a W crystal. The possibilities of analysis that our approach offers may be very useful for various applications, in particular, for structural analysis with atomic resolution.

On the correlation of angular distributions of keV ions and trajectory-dependent electronic excitations in transmission channelling geometry

“…All observed features lie well within the channelling half-angle of 2.48° calculated for 150 keV Ne in the silicon <100> channel [34]. Two Monte Carlo computational programs TRIC [27] and FLUX7 [28] were applied to simulate the ion trajectories within the Si membrane. Both codes use the Ziegler-Biersack-Littmark universal potential [35], and a binary collision model with an impact parameter dependent algorithm for energy loss.…”

“…Moreover, we have tested the applicability of two simulation packages, i.e. TRIC [27] and FLUX7 [28] for the prediction of angular distribution patterns obtained upon ion trasnmission in the keV energy regime. The latter has widely been used to study channelling phenomena at MeV energies.…”

Percolation thresholds in hydrated amphiphilic polymer membranes

“…40,41 MC codes gradually evolved into useful tools capable of unravelling the atomic structure of surfaces and interfaces. [42][43][44][45] Here Monte Carlo is applied to mimick diffusion of molecules (e.g., water) through the pores in order to probe the pore connectivity. To achieve this several thousands of tracer particles are restricted to move within the pore phase.…”

Azimuthal scans in LEIS: Influence of the scattering potential

“…The program was tested successfully in the LEIS and MEIS regimes, by comparison to results obtained from experiment [1,2] and by other simulation programs like MARLOWE [16].…”