The exposure of the miscut Si(001) surface to H gives rise to a rich sequence of stable step structures as a function of the H chemical potential. First-principles calculations of step-formation energies show that the formation of steps on the $(2\mathrm{}\times 1)$ reconstructed surface requires energy, but that on the $(1\mathrm{}\times 1)$ surface, steps form exothermically. This explains surface roughness at high H chemical potentials.

• Received 13 November 2000

DOI:https://doi.org/10.1103/PhysRevB.63.125316