Fabrication of Planar Highly Enriched Silicon by ²⁸Si Focused Ion Beam and Subsequent Experimental Optimization

This work presents an in-depth study of the role of experimental parameters in the localized ²⁸Si enrichment, via the depletion of ²⁹Si and ³⁰Si, of Si wafers using a focused ion beam. Ion implantation-induced surface recession and swelling are investigated, with the energy at which these are balanced being 37 keV. The maximum level of enrichment and its depth profile are found to vary with the ²⁸Si ion energy and ionization state, as well as the ion beam current density. Together, this enables the complex interplay of ion-induced processes that govern the enrichment to be understood more clearly and optimized. Furthermore, how modification of dynamic Monte Carlo simulations (TRYDIN) is able to demonstrate, through changing the Si surface binding energy, enables accurate reproduction of the experimentally observed results.