Wavy steps on Si(001)

Using low-energy electron microscopy we have found a new phase transition on the Si(001) surface at miscut angles smaller than {~}0.1^∘{}. The surface phase separates into facets with {~}300 {} terrace width, and regions with much larger, wavy terraces. This wavy phase is stabilized by a reduction of surface-stress-induced strain energy. A theoretical study by Tersoff and Pehlke compares favorably with our observations.