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Surface structure determination of Sn deposited on Pt(111) by low energy alkali ion scattering
~474 Surface Science 254 (1991 ) 21-28 North-Holland
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High resolution LEED studies of surface misorientation and incommensurate domain walls on reconstructed Pt(110) surface Y.-L. He, J.-K. Zuo I and G.-C. Wang PIti,sics Department, Rensselaer Polytechnic Institute, Troy, N Y 12180-3590, USA Received 6 September 1990; accepted for publication 25 February 1991 Using the unique capability of the high-resolution LEED, we can precisely measure the Bragg peak positions and angular protlles of electron diffraction beams scattered from a crystal surface. The observations reported here relate to a reconstructed Pt(!10)(1 x 2) surface at room temperature. Oscillations of the Bragg peak position and periodic variations of the FWHM of both the superlattice and integral beams along the reciprocal rods over a wide range of energies have been studied. The oscillation of the peak position of the superlattice beam results from phase shifts of electrons scattering from incommensurate (1 x 2) reconstruction domain walls between adjacent terraces. On the other hand, the oscillation of the integral-order beam is due to a surface misorientation. Furthermore, the periodic variation of the FWHM of the superlattice beam is dominated by the degree of surface misorientations~ However, the periodic variation of the FWHM associated with the integral beam results mainly from the existence of steps. Comparing the measurements with an existing model we have estimated the degree of the surface misorientation, the distribution of the incommensurate domain walls, and the lateral incommensurability on the Pt(ll0)(1 x 2) surface.
Surface Science 254 (1991) 29-44 North-Holland
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A vibrational study of borazine adsorbed on Pt(111) and Au(111) surfaces R.J. Sirnonson, M.T. Paffett, M.E. Jones 1 and B.E. Koel 2 Los Alamos National Laboratory, Los Alamos, N M 87545, USA Received 6 September 1990; accepted for publication 13 February 1991 Borazine (B3NaH6) adsorption and reaction on Pt(lll) and A u ( l l l ) substrates at 100-1000 K has been investigated using thermal desorption mass spectroscopy (TDMS), ultraviolet photoelectron spectroscopy (UPS), and high-resolution electron energy loss spectroscopy (HREELS). Submonolayer coverages of borazine decompose on P t ( l l l ) and only H z desorption is observed upon heating. Multilayer borazine desorption occurs near 150 K, with an activation energy, Ea ~ 7.3 kcal/mol. The H z desorption peaks at 300 K are followed by a very broad desorption tail extending to 900 K, which is attributed to dehydrogenation of borazine molecular fragments. In contrast, molecular adsorption of borazine on A u ( l l l ) at 110 K is thermally reversible. Molecular borazine desorption from Au(lll) occurs at 206 K with E d = 12 kcal/mol. The HREELS data show an unusual vertical orientation of the adsorbed borazine ring on P t ( l l l ) at low temperature (170 K), but indicate a binding geometry for which the plane of the ring is parallel to the Au(111) surface. Possible reasons for the striking orientational difference in adsorption geometry and reactivity on these two metals are discussed.
Surface Science 254 (1991) 45-57 North-Holland
Surface structure determination of Sn deposited on Pt(111) by low energy alkali ion scattering S.H. Overbury, D.R. Mullins Oak Ridge National Laboratory, Oak Ridge, TN 37831-6201, USA
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High resolution LEED studies of surface misorientation and incommensurate domain walls on reconstructed Pt(110) surface Y.-L. He, J.-K. Zuo I and G.-C. Wang PIti,sics Department, Rensselaer Polytechnic Institute, Troy, N Y 12180-3590, USA Received 6 September 1990; accepted for publication 25 February 1991 Using the unique capability of the high-resolution LEED, we can precisely measure the Bragg peak positions and angular protlles of electron diffraction beams scattered from a crystal surface. The observations reported here relate to a reconstructed Pt(!10)(1 x 2) surface at room temperature. Oscillations of the Bragg peak position and periodic variations of the FWHM of both the superlattice and integral beams along the reciprocal rods over a wide range of energies have been studied. The oscillation of the peak position of the superlattice beam results from phase shifts of electrons scattering from incommensurate (1 x 2) reconstruction domain walls between adjacent terraces. On the other hand, the oscillation of the integral-order beam is due to a surface misorientation. Furthermore, the periodic variation of the FWHM of the superlattice beam is dominated by the degree of surface misorientations~ However, the periodic variation of the FWHM associated with the integral beam results mainly from the existence of steps. Comparing the measurements with an existing model we have estimated the degree of the surface misorientation, the distribution of the incommensurate domain walls, and the lateral incommensurability on the Pt(ll0)(1 x 2) surface.
Surface Science 254 (1991) 29-44 North-Holland
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A vibrational study of borazine adsorbed on Pt(111) and Au(111) surfaces R.J. Sirnonson, M.T. Paffett, M.E. Jones 1 and B.E. Koel 2 Los Alamos National Laboratory, Los Alamos, N M 87545, USA Received 6 September 1990; accepted for publication 13 February 1991 Borazine (B3NaH6) adsorption and reaction on Pt(lll) and A u ( l l l ) substrates at 100-1000 K has been investigated using thermal desorption mass spectroscopy (TDMS), ultraviolet photoelectron spectroscopy (UPS), and high-resolution electron energy loss spectroscopy (HREELS). Submonolayer coverages of borazine decompose on P t ( l l l ) and only H z desorption is observed upon heating. Multilayer borazine desorption occurs near 150 K, with an activation energy, Ea ~ 7.3 kcal/mol. The H z desorption peaks at 300 K are followed by a very broad desorption tail extending to 900 K, which is attributed to dehydrogenation of borazine molecular fragments. In contrast, molecular adsorption of borazine on A u ( l l l ) at 110 K is thermally reversible. Molecular borazine desorption from Au(lll) occurs at 206 K with E d = 12 kcal/mol. The HREELS data show an unusual vertical orientation of the adsorbed borazine ring on P t ( l l l ) at low temperature (170 K), but indicate a binding geometry for which the plane of the ring is parallel to the Au(111) surface. Possible reasons for the striking orientational difference in adsorption geometry and reactivity on these two metals are discussed.
Surface Science 254 (1991) 45-57 North-Holland
Surface structure determination of Sn deposited on Pt(111) by low energy alkali ion scattering S.H. Overbury, D.R. Mullins Oak Ridge National Laboratory, Oak Ridge, TN 37831-6201, USA
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