Chlorine extraction by atomic hydrogen on Si(111)-7 x 7 surfaces

We have studied atomic-hydrogen-induced chlorine extraction on Si(111)-7x7 surfaces using photoemission spectroscopy and scanning tunneling microscopy (STM). We exposed the surface with mono- and polychloride Si to atomic hydrogen at room temperature. Photoemissions from Si 2P core level and Cl 3s level were measured before and after the atomic hydrogen dosage on the surfaces. Signals with both silicon-chlorides and Cl atoms decrease with increasing atomic hydrogen dosage. After annealing the hydrogen-exposed surface at 720 K, the STM images are very different from those of chlorine adsorbed Si(111) surface, and similar to those of hydrogen-covered Si(111) surfaces after the annealing. We conclude that chlorine atoms are extracted from the Cl/Si(111) surface by atomic hydrogen, and the surface Si atoms are terminated by hydrogens. (C) 1999 Elsevier Science B.V. All rights reserved.