Deformation of octahedra at LaB6(100) surface studied by HREELS

A391 The energy and angular distribution of the electron-stimulated O + ion yield have been measured from clean and SO2-dosed rutile TiO2(ll0). ESD spectra from the clean surface indicate ion emission at three energies: 2.5, 4.0 and 6.5 eV. By comparison with previous calculations, the 4.0 and 6.5 eV features can be assigned to emission of in-plane and bridging O atoms, respectively. The elongation of the ESDIAD image in the [110] azimuth is consistent with that predicted for the in-plane O atoms. While the O + energy distribution changes significantly following SO 2 adsorption at 130 K and again following sequential annealing, there is little change to the ESDIAD pattern. The latter result is consistent with emission from surface sulphate species, although it could also be due to a residual substrate effect.

Surface Science 287/288 (1993) 391-395 North-Holland

Deformation of octahedra at LaB (100) surface studied by HREELS T. Nagao, T. Kitamura, T. Iizuka, M. Umeuchi, C. Oshima 1 Department of Applied Physics, Waseda University, Shinjyuku, Tokyo 169, Japan

and S. Otani National Institute for Research in Inorganic Materials, Namiki 1-1, Tsukuba, Ibaraki 305, Japan Received 1 September 1992; accepted for publication 24 November 1992 The surface phonons of LAB6(100) surface have been investigated by means of high resolution electron energy spectroscopy. the clean surface we have observed 8 loss peaks in the off-specular spectra, of which the higher energy losses are related to vibrations of the three-dimensional network of boron. Theoretical analysis based on a force constant model strongly suggests deformation of the three-dimensional network of boron; the topmost octahedra are expanded by ~ 0.004 nm parallel to surface.

On the the the

Surface Science 287/288 (1993) 396-399 North-Holland

Surface structure of MoS2(001) determined by coaxial impact-collision ion scattering spectroscopy (CAICISS) Y. Kadowaki, K. Aika Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 227, Japan

H. Kondoh and H. Nozoye * National Institute of Materials and Chemical Research, 1-1 Higashi, Tsukuba, Ibaraki 305, Japan Received 1 September 1992; accepted for publication 19 November 1992 Stacking sequence and relaxation of the natural MoS2(001) surface structure were determined with coaxial impact collision ion scattering spectroscopy (CAICISS) under ultra high vacuum. We concluded that the surface stacking sequence of MoS 2 is hexagonal and there is no lateral translation of atomic layers near the surface. We also determined that the interlayer spacing contracts by 3.6 + 0.4% for the top interlayer (d12) and by 0 to 2% for the subsequent interlayer (d23).