Formation and reactivity of high quality halogen terminated Si(1Â 1Â 1) surfaces

High quality halogenated silicon surfaces have been produced using gas phase reactions of H-terminated Si(1 1 1) with molecular chlorine or bromine at room temperature. STM images show that the resulting surfaces maintain the low defect densities of H/Si(1 1 1). High resolution electron energy loss spectra confirm halogenation of the surface through the observation of the Si-Cl or Si-Br stretch modes and also indicate the absence of significant oxidation or contamination of the surface even after brief air exposure. While chlorine terminated surfaces are found to be surprisingly stable to exposure to water vapour, dipping in water destroys the surface by insertion of oxygen into silicon backbonds and formation of terminal H and O-H groups. In lab air, oxidation is observed to proceed rather slowly and in a patch-like fashion with substantial chlorine still present after >10 h exposure.