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Surface states, electronic structure and surface energy of the Ag(001) surface
A93 Surface Science 243 (1991) 309-316 North-Holland
309
The, role of Auger processes in slow collisions of Li ÷ ions with cesiated W(110) surfaces H. Brenten, H. Mt~ller, K.H. Knorr, D. Kruse, H. Schall and V. Kempter Physikalisches Institut der Technischen Universitiit Clausthal, Leibnizstrasse 4, W-3392 Clausthal-Zellerfeld, Germany Received 6 July 1990; accepted for publication 6 September 1990 We have investigated 1000 eV Li + collisions under grazing incidence with partially cesiated W(ll0) surfaces by energy analysis of the ejected electrons and the Li + and Li- ions scattered into 45 o. The Li ion fraction and the electron yield are correlated with the coverage dependence of the work function, and both show maxima near the work function minimum. The maximum total electron yield is 0.12 electrons/incident ion between 200 and 1000 eV. The Li ÷ intensity and the Li(2p-2s) photon yield behave quite differently showing maxima near 0.2 ML Cs coverage and a marked decrease towards larger coverages. From the energy analysis of the ejected electrons it is concluded that Auger deexcitation of excited Li states populated by resonant charge transfer between the Li + projectile and the partially cesiated surface is an efficient process
Surface Science 243 (1991) 317-322 North-Holland
317
Surface states, electronic structure and surface energy of the Ag(001) surface H. Erschbaumer, A.J. Freeman Department of Physics and Astronomy, Northwestern University, Evanston, 1L 60208-3112, USA
C.L. Fu Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
and R. Podloucky Institute for Physical Chemistry, University of Vienna, Wien, Austria Received 25 June 1990; accepted for publication 18 September 1990 Surface states, electronic structure and surface energy of a clean Ag(001) surface are determined using the local density full potential linearized augmented plane wave calculations for an 11 layer slab.
Surface Science 243 (1991) 323-333 North-Holland
323
The bonding site location of chemisorbed oxygen on AI(100) from angle resolved secondary ion mass spectrometry L.L. Lauderback 1,, A.J. Lynn, C.J. Waltman and S.A. Larson Department of Chemical Engineering, University of Colorado, Boulder, CO 80309-0424, USA Received 23 April 1990; accepted for publication 14 September 1990 Angle resolved SIMS measurements of the azimuthal angle distribution of O - ions ejected from chemisorbed oxygen adlayers on AI(100) are compared with the predictions of a molecular dynamics model of the ejection process for oxygen chemisorbed at various high symmetry sites above an below the AI(100) surface. The molecular dynamics simulations predict that the angle distribution of ejected oxygen is very sensitive to the oxygen bonding site location, both with respect to registry with the substrate and distance above and below the surface A1 plane. The experimental measurements show that the azimuthal angle distribution of the ejected O ions is essentially isotopic for ejection at polar angles ranging from 33 to 65 o (measured from the surface normal) with kinetic energies of the O - ions ranging from 2 to 20 eV. The measured O - azimuthal angle distributions are shown to be in agreement with the predictions of the molecular dynamics simulations only when oxygen is chemisorbed within or slightly below the surface A1 plane at four-fold hollow sites.
309
The, role of Auger processes in slow collisions of Li ÷ ions with cesiated W(110) surfaces H. Brenten, H. Mt~ller, K.H. Knorr, D. Kruse, H. Schall and V. Kempter Physikalisches Institut der Technischen Universitiit Clausthal, Leibnizstrasse 4, W-3392 Clausthal-Zellerfeld, Germany Received 6 July 1990; accepted for publication 6 September 1990 We have investigated 1000 eV Li + collisions under grazing incidence with partially cesiated W(ll0) surfaces by energy analysis of the ejected electrons and the Li + and Li- ions scattered into 45 o. The Li ion fraction and the electron yield are correlated with the coverage dependence of the work function, and both show maxima near the work function minimum. The maximum total electron yield is 0.12 electrons/incident ion between 200 and 1000 eV. The Li ÷ intensity and the Li(2p-2s) photon yield behave quite differently showing maxima near 0.2 ML Cs coverage and a marked decrease towards larger coverages. From the energy analysis of the ejected electrons it is concluded that Auger deexcitation of excited Li states populated by resonant charge transfer between the Li + projectile and the partially cesiated surface is an efficient process
Surface Science 243 (1991) 317-322 North-Holland
317
Surface states, electronic structure and surface energy of the Ag(001) surface H. Erschbaumer, A.J. Freeman Department of Physics and Astronomy, Northwestern University, Evanston, 1L 60208-3112, USA
C.L. Fu Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
and R. Podloucky Institute for Physical Chemistry, University of Vienna, Wien, Austria Received 25 June 1990; accepted for publication 18 September 1990 Surface states, electronic structure and surface energy of a clean Ag(001) surface are determined using the local density full potential linearized augmented plane wave calculations for an 11 layer slab.
Surface Science 243 (1991) 323-333 North-Holland
323
The bonding site location of chemisorbed oxygen on AI(100) from angle resolved secondary ion mass spectrometry L.L. Lauderback 1,, A.J. Lynn, C.J. Waltman and S.A. Larson Department of Chemical Engineering, University of Colorado, Boulder, CO 80309-0424, USA Received 23 April 1990; accepted for publication 14 September 1990 Angle resolved SIMS measurements of the azimuthal angle distribution of O - ions ejected from chemisorbed oxygen adlayers on AI(100) are compared with the predictions of a molecular dynamics model of the ejection process for oxygen chemisorbed at various high symmetry sites above an below the AI(100) surface. The molecular dynamics simulations predict that the angle distribution of ejected oxygen is very sensitive to the oxygen bonding site location, both with respect to registry with the substrate and distance above and below the surface A1 plane. The experimental measurements show that the azimuthal angle distribution of the ejected O ions is essentially isotopic for ejection at polar angles ranging from 33 to 65 o (measured from the surface normal) with kinetic energies of the O - ions ranging from 2 to 20 eV. The measured O - azimuthal angle distributions are shown to be in agreement with the predictions of the molecular dynamics simulations only when oxygen is chemisorbed within or slightly below the surface A1 plane at four-fold hollow sites.