Scanning tunneling microscopy study of hydrogen-terminated Si(001) surfaces after wet cleaning

A scanning tunneling microscopy (STM) study of the atomic structure of hydr ogen-terminated Si(001) surfaces after wet cleaning is presented. Surface m orphologies strongly depend on wet cleaning procedures. After bring dipped into dilute HF solution, the surface is constructed by piling round, small terraces along the [110] direction. On the other hand, atomic rows along th e [110] direction are clearly observed when the surface is subsequently rin sed by ultrapure water, and the corrugation pattern is identified as a 2 x 1 structure. With STM and Fourier-transform infrared attenuated total refle ction (FTIR-ATR) observations, it is proposed that etching with ultrapure w ater proceeds in two steps. First, atomic steps perpendicular to dihydride rows of the upper layer are etched quickly to form step edges parallel to t he dihydride rows and to produce large terraces with fewer steps. Second, e tching occurs inside a terrace. Every other row of an ideally 1 x 1 dihydri de terrace is removed preferentially in ultrapure water. (C) 2000 Elsevier Science B.V. All rights reserved.