Stabilities of single-layer and bilayer steps on Si(001) surfaces

Abstract

The formation energies of single- and double-layer steps on Si(001) surfaces were calculated. For each case, two configurations with surface dimerization axes normal or parallel to the step edge were examined. Single-layer steps are found to have the lowest formation energy. Bilayer steps become energetically more favorable on surfaces misoriented towards [110] or [1\ifmmode\bar\else\textasciimacron\fi{}10] axes where low- and high-energy single-layer steps are forced to alternate with each other.