Equilibrium structures of Si(100) stepped surfaces

Atomistic calculations using the Stillinger-Weber interatomic potential show that stress relaxation can lower the energy of a Si(100) stepped surface below that of the flat surface. Two types of elastic interactions are identified: One is due to stress anisotropy which occurs only on single-stepped surfaces and has a logarithmic dependence on ledge separation l; the other is associated with ledge rebonding, present in both single- and double-stepped surfaces, and has a variation of ${\mathit{l}}^{\mathrm{-}2}$. On the vicinal Si(001), single-layer ledges are predicted to be favored over double-layer ledges at low miscut angles with the crossover occurring at about 1° at zero temperature, and at 3° at 500 K, in agreement with experiment.