Hybrid Reverse Monte Carlo and electron phase contrast image simulations of amorphous silicon with and without paracrystals

Abstract

Atomic networks of as-implanted and relaxed amorphous silicon solids were simulated using a Hybrid Reverse Monte Carlo algorithm constrained by high-resolution electron diffraction data. No significant structural distinction was observed between the two forms of amorphous silicon. A nanometer-sized crystallite was inserted into the as-implanted structure, to model medium-range order due to paracrystals, and the atomic network was energetically relaxed whilst maintaining consistency with experiment. Experimental pair–pair correlations were then simulated using a stochastic generalised Debye sum of fourth order. The idealised pair–pair correlation calculations were not able to readily distinguish between models with and without paracrystals. On the other hand, wave mechanical simulations surprisingly showed that paracrystals could be experimentally imaged using phase contrast transmission electron microscopy and/or nanoscale electron diffraction on a contemporary aberration-corrected microscope.