ENERGETICS AND STRUCTURE OF THE STABLE AND UNSTABLE BIATOMIC STEP EDGES OF SI(001)

The atomic geometry of Si(001) with a misorientation of 4.5 degrees to wards [110] has been studied with scanning tunneling microscopy. Speci al attention has been paid to the buckling registry of the dimers and atoms near the biatomic step edge. For the arrangement of the atoms ne ar the steps and at kink positions some simple rules are given. The bi atomic step edge formation energies have been determined by analyzing the step edge roughness. The ordering of the various types of step edg es is in perfect agreement with total energy calculations performed by Chadi [Phys. Rev. Lett. 59, 1691 (1987)]. Finally, the transition fro m a surface with single steps to a surface with double steps has been calculated to occur at a miscut angle of 1.5 degrees.