ADSORBATE-INDUCED RECONSTRUCTION ON SI(001) PROBED BY RESONANT OPTICAL 2ND-HARMONIC GENERATION

The recent development of easily tuneable pulsed lasers has made spect roscopic optical second harmonic generation (SHG) studies routinely po ssible, although little work has been published. Spectroscopic SHG fro m Si(001) surfaces in the region of 3.3 eV is reported here, Adsorptio n of Sb on a clean Si(001)-1 X 2 surface, followed by annealing, produ ces Si(001)-1 X 1-Sb and then Si(001)-2 X 1-Sb. The results obtained a re consistent with an unusual model of the Si(001)-1 x 1-Sb surface st ructure, which comprises isolated Sb atoms bonded to two bulk-like Si atoms. The Sb atoms only form dimers on further annealing to produce t he Si(001)-2 X 1-Sb structure.