ATOMIC STRUCTURES OF HYDROGEN-TERMINATED SI(001) SURFACES AFTER WET CLEANING BY SCANNING-TUNNELING-MICROSCOPY

Scanning tunneling microscopy observations are performed on a H-termin ated Si(001) surface treated with HF solutions and ultrapure water wit h very low dissolved oxygen and total organic carbon contents. Over a large area, row structures are observed in [110] and [1 (1) over bar 0 ] directions. Pyramidal-shaped etch pits are also observed, which are caused by anisotropic etching by OH ions. Detailed images clearly show 2 X 1 periodic structures. It is suggested that every other row of th e ideally dihydride 1 X 1 surface is etched preferentially by OH ions. This explains the mechanism by which the smallest etch pits are forme d. (C) 1998 American Institute of Physics. [S0003-6951(98)01839-7].