Step-Step Interactions on Vicinial Si(100)

We have measured probability distributions of inter-step spacing on vicinial double-stepped Si(100) surfaces with a STM. Steps are observed to strongly avoid one another on a room temperature surface after anneal and quench. The step-step interaction energies can be explained by elastic strain interactions, if the thermodynamics of the kinks is taken into account. The step edges are found to be stiff, with many dimers moving as a unit. We present models of kink energies and step-step interactions which are consistent with the data.