Scanning tunneling microscopy of silicon surfaces in air: Observation of atomic images

Atomic images were successfully observed on hydrogen terminated Si (100) and (111) surfaces in air by scanning tunneling microscopy. The surfaces were prepared by ultraviolet irradiation in an oxygen atmosphere followed by dipping in 1% hydrofluoric acid. For the (100) surface, the atomic images exhibit various structures such as rows along the [010] and [001] directions, an apparent (1/(2)^1/2×1/(2)^1/2)R45° ‘‘sublattice,’’ and a c(2×1) superlattice in addition to the square lattice corresponding to the Si(100)‐(1×1) structure. For the (111) surface, a triangular lattice pattern which agrees with the Si(111)‐(1×1) structure was observed. Such atomic images appeared in restricted areas. It is possible that slight oxidation or some adsorption enables or prevents the observation of atomic images.