Long-range ledge-ledge interactions on Si(111) surfaces

Surface ledges of the [211̄] and [2̄11] type on the Si(111) surface provide a dilational contribution to the strongly compressive surface stress tensor. Computer calculations using a semiempirical potential energy function show (a) monatomic ledge-ledge interaction even at spacings of 50 Å, (b) strong reconstruction on some ledge orientations and negligible changes on others leading to ledge energies in the range 0.01–0.22 eV/atom compared to a face energy of 0.38 eV/atom, and (c) that the surface stress tensor dominates the relaxation around ledges.