An atomistic assessment of the impact of flaw orientation on the elastic and failure behavior of single-crystal Si nanometre-thick slabs

Failure of nanoscale Si thin films was examined using molecular dynamics (MD) simulations that employed the modified embedded atom method (MEAM) interatomic potential. Specifically, nanometre-thick slabs of different crystallographic orientations containing asymmetric, high aspect ratio surface flaws were subjected to uniaxial tensile strains with the strain applied perpendicular to the flaw major axis. The ensuing elastic response and failure behaviour were examined as a function of variation in crystallographic orientation relative to the surface flaw. For certain flaw orientations, crack propagation was accompanied by slip along preferred directions, while in other cases, failure was purely brittle. In addition, a significant dependence of the computed elastic constants and yield stress, on the relative orientation of the surface flaw was observed. This work offers new insights into the role of surface flaws on the mechanical failure of silicon-based, nanoscale, engineered structures.