A MD study of low energy boron bombardment on silicon

Abstract

Low energy boron bombardment of silicon has been simulated at room temperature by means of molecular dynamics (MD). Tersoff potential T3 was used in the simulation smoothly linked to the universal potential. The boron–silicon interaction was simulated following the ideas of Tersoff for the SiC potential but modified to take into account, in the B–Si interaction, whether or not the neighbours of either of both are entirely or partially boron or silicon atoms. (001) Si–C with (2×1) reconstruction surface was bombarded with boron at energies of 200 and 500 eV, which were initially chosen as good representative values of the low energy range of interest. Reliable results require a reasonable good statistic so that 100 impact points were chosen which were uniformly distributed over a representative area of a (2×1) surface.Special care was taken to determine the kind of damage produced in a Si crystal by the slowing down of boron. It is described in detail the way to determine vacancies and interstitials. The damage produced can be classified in regions were the accumulation of damage does not allow to identify properly the type of defects produced and regions in which defects are isolated and can be beautifully identified in terms of the potential energy variation and the displacements of their neighbours. Clusters of vacancies and interstitials are determined. Mean number of interstitials, vacancies, adatoms, sputtering, etc. are summarised in a table. Range distributions of boron are also determined.