We report an oxygen-induced metastable ordered structure on a Si(001) surface. The c(4×4) structure is obtained after extensive annealing of a clean Si(001)-2×1 surface dosed with oxygen at room temperature. This c(4×4) structure appears only after the completion of the 2×1 structure, which disappears in the early annealing stage. The c(4×4) structure reverts back irreversibly to the 2×1 structure after the surface is heated to above 720 °C. Possible structural models for the c(4×4) reconstruction are discussed.

• Received 20 June 1994

DOI:https://doi.org/10.1103/PhysRevB.50.11200