A32
Masashi Oshima ~, Hatsumi Mori 2, Hideki Yamochi 3 and Gunzi Saito .t Institute for Solid State Physics, The University of Tokyo, Roppongt, Minato-ku, Tokyo 106, Japan Received 13 June 1990; accepted for publication 6 July 1990 The bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) molecules in the surface cation layer of the (BEDT-TrF)2KHg(SCN) 4 crystal were observed by scanning tunneling microscopy (STM). The obtained arrangement of BEDT-TrF was in good agreement with that expected from the structure determined by X-ray diffraction. In addition, some subsidiary images were observed around the K and Hg ion positions. The STM image of the BEDT-TTF molecules was influenced by the structure of the anion layer on them, and they showed a strong bias dependence.
Surface Science 242 (1991) 23-31 North-Holland
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Surface step configurations under strain: kinetics and step-step interactions M.B. Webb, F.K. Men, B.S. Swartzentruber, R. Kariotis and M.G. Lagally University of Wisconsin-Madison, Madison, WI 53706, USA Received 5 June 1990; accepted for publication 15 June 1990 Strain is an important ingredient in the physics of surfaces as has been shown in experiments with thin films and alloys; It is desirable to have strain as an externally applied and continuous variable. We have studied the effect of strain by loading a cantilevered bar and observing the effects on the surface with both LEED and the STM. On the Si(100) surface, strain produces a reversible asymmetry in the relative population of the 2 × 1 and 1 × 2 domains. This requires the motion of monatomic steps which are the domain boundaries. The effect is driven by the relaxation of the energy associated with a long-range strain field extending into the bulk due to the anisotropy of the intrinsic stress tensor of the two reconstructed domains. It is similar to magnetic domain structures reducing the magnetic field energy. These long-range strain fields have important consequences for a number of surface phenomena. Here we first report experiments on the terrace width distributions which gives information about the effective step-step interactions. Then we report experiments on the kinetics of the step migration which gives information about surface diffusion.
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Surface Science 242 (1991) 32-38 North-Holland
Rearrangement of surface steps of the Ni(7 911) surface by hydrogen adsorption Hidetoshi Namba, Yuji Okawa and Haruo Kuroda Research Center for Spectrochemistry and Department of Chemistry, Faculty of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan Received 15 May 1990; accepted for publication 30 July 1990 Chemisorption of hydrogen on a Ni(7 911) stepped surface was studied by LEED, AES, UPS and work function measurements. Atomic hydrogen is chemisorbed on this surface and causes a rearrangement of steps. Hydrogen molceafle,s are found to be inactive for such an effect. It is concluded that the step rearrangement is induced by the incorporation of atomic hydrogen into the subsurface region through step sites. Structural models for the step-rearranged states produced by hydrogen chemisorption are discussed.