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The adsorption of selenium on a W(100) surface
A101 Surface Science 115 (1982) 1-14 North-Holland Publishing Company
I
THE ADSORPTION OF SELENIUM ON A W(100) SURFACE Ch. PARK, H.M. KRAMER and E. B A U E R Physikalisches Institut, Technische Universiti~t Clausthal, D-3392 ClausthaI-Zellerfe/d and SFB 126 Gi~ttmgen-Clausthal, Fed. Rep. of Germany Received 13 September 1981 ; accepted for publication 9 November 1981 The adsorption of Se from an electrochemical cell on a W(100) surface at various temperatures is studied by Auger electron spectroscopy (AES), low energy electron diffraction (LEED), work function change measurements (Aqb) and thermal desorption spectroscopy (TDS) without and with thermal annealing. A large number of superstructures is found in LEED which are attributed to adsorption layers on an unreconstructed surface, using AES for relative coverage calibration. The TDS spectra indicate a complex desorption behaviour for coverages above about 0.5 monolayers (ML).
Surface Science 115 (1982) 15-36 North-Holland Publishing Company
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A CLUSTER MODEL OF THE CHEMISORPTION OF ATOMIC Li, O AND Na BY THE (111) SURFACE OF AI B.N. COX * Joint Institute for ,4dvancement of Flight Sciences, The George Washington University, N,4 S,4 -Langley Research Center, Hampton, Virginia 23665, USA
and
C.W. BAUSCHLICHER, Jr. Polyatomics Research Incorporated, 1101 "San ,4ntonio Road, Suite 420, Mr. View, California 94043, USA Received 9 June 1981; accepted for publicaton 12 November 1981 Hartree-Fock calculations are presented for a cluster of nineteen aluminum atoms representing the AI(111) surface. The chemisorption of Li, O, and Na over an open, three-fold site is studied. It is found that oxygen adsorbs initially as a negative singly ionized species at a perpendicular distance of (I.3-0.2)a 0 from the surface with appreciable covalent character in the bonding. This adsorption site is separated by a barrier of -- 1 eV from another stable site under the surface in an octahedral interstice, where the O atom is doubly ionized. Na and Li are found to adsorb as positive singly ionized species, and to have low activation energies (0.04 eV and 0.09 eV) for surface diffusion. Calculations of dipole moments are reported, which in comparison with experiment support the geometric predictions of the model calculations.
I
THE ADSORPTION OF SELENIUM ON A W(100) SURFACE Ch. PARK, H.M. KRAMER and E. B A U E R Physikalisches Institut, Technische Universiti~t Clausthal, D-3392 ClausthaI-Zellerfe/d and SFB 126 Gi~ttmgen-Clausthal, Fed. Rep. of Germany Received 13 September 1981 ; accepted for publication 9 November 1981 The adsorption of Se from an electrochemical cell on a W(100) surface at various temperatures is studied by Auger electron spectroscopy (AES), low energy electron diffraction (LEED), work function change measurements (Aqb) and thermal desorption spectroscopy (TDS) without and with thermal annealing. A large number of superstructures is found in LEED which are attributed to adsorption layers on an unreconstructed surface, using AES for relative coverage calibration. The TDS spectra indicate a complex desorption behaviour for coverages above about 0.5 monolayers (ML).
Surface Science 115 (1982) 15-36 North-Holland Publishing Company
15
A CLUSTER MODEL OF THE CHEMISORPTION OF ATOMIC Li, O AND Na BY THE (111) SURFACE OF AI B.N. COX * Joint Institute for ,4dvancement of Flight Sciences, The George Washington University, N,4 S,4 -Langley Research Center, Hampton, Virginia 23665, USA
and
C.W. BAUSCHLICHER, Jr. Polyatomics Research Incorporated, 1101 "San ,4ntonio Road, Suite 420, Mr. View, California 94043, USA Received 9 June 1981; accepted for publicaton 12 November 1981 Hartree-Fock calculations are presented for a cluster of nineteen aluminum atoms representing the AI(111) surface. The chemisorption of Li, O, and Na over an open, three-fold site is studied. It is found that oxygen adsorbs initially as a negative singly ionized species at a perpendicular distance of (I.3-0.2)a 0 from the surface with appreciable covalent character in the bonding. This adsorption site is separated by a barrier of -- 1 eV from another stable site under the surface in an octahedral interstice, where the O atom is doubly ionized. Na and Li are found to adsorb as positive singly ionized species, and to have low activation energies (0.04 eV and 0.09 eV) for surface diffusion. Calculations of dipole moments are reported, which in comparison with experiment support the geometric predictions of the model calculations.