The interaction of dichloromonosilane (SiH2Cl2) with Si(100)-(2 x 1) was investigated with scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy under ultrahigh vacuum conditions. Photoelectron spectroscopy measurements after saturation exposure at temperatures between 300 and 1070 K show only monochlorides on the surface, with the Cl coverage passing through a maximum with increasing adsorption temperature at a given SiH2Cl2 flux. STM shows that at least one pathway for decomposition of SiH2Cl2 proceeds via the formation of silylene groups. At an adsorption temperature of 690 K the molecular fragments can completely decompose into their atomic constituents, Had and CIA adsorbates are mobile on the surface at 690 K and higher temperatures and form small islands. Si adatoms form epitaxial dimer strings without adsorbate termination. Preferential adsorbate-termination of substrate SB steps leads to an increased island density as compared to molecular beam epitaxy. Annealing saturated surfaces to 1000 K leads to c(4 x 4) structures and vacancy line defects. The latter consist mainly of single dimer vacancies. Mobility and lateral interaction of dimer vacancies leads to formation of the dimer vacancy lines which release the anisotropic surface stress. The metastable surface structures support a mechanism for desorption of SiCl2 under formation of dimer vacancies. (C) 2001 Elsevier Science B.V. All rights reserved. References: 83
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