Published online by Cambridge University Press: 28 February 2011
Primitive (001) surfaces contain only biatomic (ao/2) steps and thereby provide a topological way of suppressing antiphase domain formation in polar materials heteroepitaxially grown on nonpolar (001) substrates. We show that thermodynamic equilibrium is a necessary and sufficient condition to form primitive (001) Si surfaces due to a π-bonded step reconstruction that lowers the relative enthalpy of reconstructed [110] biatomic steps by 0.04 eV per step atom, and to correlation, which freezes out the step configurational entropy thereby suppressing the formation of all other types of steps. Implications for general vicinal (001) Si surfaces are discussed.